| :mod:`socket` --- Low-level networking interface |
| ================================================ |
| |
| .. module:: socket |
| :synopsis: Low-level networking interface. |
| |
| **Source code:** :source:`Lib/socket.py` |
| |
| -------------- |
| |
| This module provides access to the BSD *socket* interface. It is available on |
| all modern Unix systems, Windows, MacOS, and probably additional platforms. |
| |
| .. note:: |
| |
| Some behavior may be platform dependent, since calls are made to the operating |
| system socket APIs. |
| |
| .. index:: object: socket |
| |
| The Python interface is a straightforward transliteration of the Unix system |
| call and library interface for sockets to Python's object-oriented style: the |
| :func:`.socket` function returns a :dfn:`socket object` whose methods implement |
| the various socket system calls. Parameter types are somewhat higher-level than |
| in the C interface: as with :meth:`read` and :meth:`write` operations on Python |
| files, buffer allocation on receive operations is automatic, and buffer length |
| is implicit on send operations. |
| |
| |
| .. seealso:: |
| |
| Module :mod:`socketserver` |
| Classes that simplify writing network servers. |
| |
| Module :mod:`ssl` |
| A TLS/SSL wrapper for socket objects. |
| |
| |
| Socket families |
| --------------- |
| |
| Depending on the system and the build options, various socket families |
| are supported by this module. |
| |
| The address format required by a particular socket object is automatically |
| selected based on the address family specified when the socket object was |
| created. Socket addresses are represented as follows: |
| |
| - The address of an :const:`AF_UNIX` socket bound to a file system node |
| is represented as a string, using the file system encoding and the |
| ``'surrogateescape'`` error handler (see :pep:`383`). An address in |
| Linux's abstract namespace is returned as a :term:`bytes-like object` with |
| an initial null byte; note that sockets in this namespace can |
| communicate with normal file system sockets, so programs intended to |
| run on Linux may need to deal with both types of address. A string or |
| bytes-like object can be used for either type of address when |
| passing it as an argument. |
| |
| .. versionchanged:: 3.3 |
| Previously, :const:`AF_UNIX` socket paths were assumed to use UTF-8 |
| encoding. |
| |
| .. versionchanged:: 3.5 |
| Writable :term:`bytes-like object` is now accepted. |
| |
| .. _host_port: |
| |
| - A pair ``(host, port)`` is used for the :const:`AF_INET` address family, |
| where *host* is a string representing either a hostname in Internet domain |
| notation like ``'daring.cwi.nl'`` or an IPv4 address like ``'100.50.200.5'``, |
| and *port* is an integer. |
| |
| - For IPv4 addresses, two special forms are accepted instead of a host |
| address: ``''`` represents :const:`INADDR_ANY`, which is used to bind to all |
| interfaces, and the string ``'<broadcast>'`` represents |
| :const:`INADDR_BROADCAST`. This behavior is not compatible with IPv6, |
| therefore, you may want to avoid these if you intend to support IPv6 with your |
| Python programs. |
| |
| - For :const:`AF_INET6` address family, a four-tuple ``(host, port, flowinfo, |
| scope_id)`` is used, where *flowinfo* and *scope_id* represent the ``sin6_flowinfo`` |
| and ``sin6_scope_id`` members in :const:`struct sockaddr_in6` in C. For |
| :mod:`socket` module methods, *flowinfo* and *scope_id* can be omitted just for |
| backward compatibility. Note, however, omission of *scope_id* can cause problems |
| in manipulating scoped IPv6 addresses. |
| |
| .. versionchanged:: 3.7 |
| For multicast addresses (with *scope_id* meaningful) *address* may not contain |
| ``%scope_id`` (or ``zone id``) part. This information is superfluous and may |
| be safely omitted (recommended). |
| |
| - :const:`AF_NETLINK` sockets are represented as pairs ``(pid, groups)``. |
| |
| - Linux-only support for TIPC is available using the :const:`AF_TIPC` |
| address family. TIPC is an open, non-IP based networked protocol designed |
| for use in clustered computer environments. Addresses are represented by a |
| tuple, and the fields depend on the address type. The general tuple form is |
| ``(addr_type, v1, v2, v3 [, scope])``, where: |
| |
| - *addr_type* is one of :const:`TIPC_ADDR_NAMESEQ`, :const:`TIPC_ADDR_NAME`, |
| or :const:`TIPC_ADDR_ID`. |
| - *scope* is one of :const:`TIPC_ZONE_SCOPE`, :const:`TIPC_CLUSTER_SCOPE`, and |
| :const:`TIPC_NODE_SCOPE`. |
| - If *addr_type* is :const:`TIPC_ADDR_NAME`, then *v1* is the server type, *v2* is |
| the port identifier, and *v3* should be 0. |
| |
| If *addr_type* is :const:`TIPC_ADDR_NAMESEQ`, then *v1* is the server type, *v2* |
| is the lower port number, and *v3* is the upper port number. |
| |
| If *addr_type* is :const:`TIPC_ADDR_ID`, then *v1* is the node, *v2* is the |
| reference, and *v3* should be set to 0. |
| |
| - A tuple ``(interface, )`` is used for the :const:`AF_CAN` address family, |
| where *interface* is a string representing a network interface name like |
| ``'can0'``. The network interface name ``''`` can be used to receive packets |
| from all network interfaces of this family. |
| |
| - :const:`CAN_ISOTP` protocol require a tuple ``(interface, rx_addr, tx_addr)`` |
| where both additional parameters are unsigned long integer that represent a |
| CAN identifier (standard or extended). |
| - :const:`CAN_J1939` protocol require a tuple ``(interface, name, pgn, addr)`` |
| where additional parameters are 64-bit unsigned integer representing the |
| ECU name, a 32-bit unsigned integer representing the Parameter Group Number |
| (PGN), and an 8-bit integer representing the address. |
| |
| - A string or a tuple ``(id, unit)`` is used for the :const:`SYSPROTO_CONTROL` |
| protocol of the :const:`PF_SYSTEM` family. The string is the name of a |
| kernel control using a dynamically-assigned ID. The tuple can be used if ID |
| and unit number of the kernel control are known or if a registered ID is |
| used. |
| |
| .. versionadded:: 3.3 |
| |
| - :const:`AF_BLUETOOTH` supports the following protocols and address |
| formats: |
| |
| - :const:`BTPROTO_L2CAP` accepts ``(bdaddr, psm)`` where ``bdaddr`` is |
| the Bluetooth address as a string and ``psm`` is an integer. |
| |
| - :const:`BTPROTO_RFCOMM` accepts ``(bdaddr, channel)`` where ``bdaddr`` |
| is the Bluetooth address as a string and ``channel`` is an integer. |
| |
| - :const:`BTPROTO_HCI` accepts ``(device_id,)`` where ``device_id`` is |
| either an integer or a string with the Bluetooth address of the |
| interface. (This depends on your OS; NetBSD and DragonFlyBSD expect |
| a Bluetooth address while everything else expects an integer.) |
| |
| .. versionchanged:: 3.2 |
| NetBSD and DragonFlyBSD support added. |
| |
| - :const:`BTPROTO_SCO` accepts ``bdaddr`` where ``bdaddr`` is a |
| :class:`bytes` object containing the Bluetooth address in a |
| string format. (ex. ``b'12:23:34:45:56:67'``) This protocol is not |
| supported under FreeBSD. |
| |
| - :const:`AF_ALG` is a Linux-only socket based interface to Kernel |
| cryptography. An algorithm socket is configured with a tuple of two to four |
| elements ``(type, name [, feat [, mask]])``, where: |
| |
| - *type* is the algorithm type as string, e.g. ``aead``, ``hash``, |
| ``skcipher`` or ``rng``. |
| |
| - *name* is the algorithm name and operation mode as string, e.g. |
| ``sha256``, ``hmac(sha256)``, ``cbc(aes)`` or ``drbg_nopr_ctr_aes256``. |
| |
| - *feat* and *mask* are unsigned 32bit integers. |
| |
| .. availability:: Linux 2.6.38, some algorithm types require more recent Kernels. |
| |
| .. versionadded:: 3.6 |
| |
| - :const:`AF_VSOCK` allows communication between virtual machines and |
| their hosts. The sockets are represented as a ``(CID, port)`` tuple |
| where the context ID or CID and port are integers. |
| |
| .. availability:: Linux >= 4.8 QEMU >= 2.8 ESX >= 4.0 ESX Workstation >= 6.5. |
| |
| .. versionadded:: 3.7 |
| |
| - :const:`AF_PACKET` is a low-level interface directly to network devices. |
| The packets are represented by the tuple |
| ``(ifname, proto[, pkttype[, hatype[, addr]]])`` where: |
| |
| - *ifname* - String specifying the device name. |
| - *proto* - An in network-byte-order integer specifying the Ethernet |
| protocol number. |
| - *pkttype* - Optional integer specifying the packet type: |
| |
| - ``PACKET_HOST`` (the default) - Packet addressed to the local host. |
| - ``PACKET_BROADCAST`` - Physical-layer broadcast packet. |
| - ``PACKET_MULTIHOST`` - Packet sent to a physical-layer multicast address. |
| - ``PACKET_OTHERHOST`` - Packet to some other host that has been caught by |
| a device driver in promiscuous mode. |
| - ``PACKET_OUTGOING`` - Packet originating from the local host that is |
| looped back to a packet socket. |
| - *hatype* - Optional integer specifying the ARP hardware address type. |
| - *addr* - Optional bytes-like object specifying the hardware physical |
| address, whose interpretation depends on the device. |
| |
| - :const:`AF_QIPCRTR` is a Linux-only socket based interface for communicating |
| with services running on co-processors in Qualcomm platforms. The address |
| family is represented as a ``(node, port)`` tuple where the *node* and *port* |
| are non-negative integers. |
| |
| .. versionadded:: 3.8 |
| |
| - :const:`IPPROTO_UDPLITE` is a variant of UDP which allows you to specify |
| what portion of a packet is covered with the checksum. It adds two socket |
| options that you can change. |
| ``self.setsockopt(IPPROTO_UDPLITE, UDPLITE_SEND_CSCOV, length)`` will |
| change what portion of outgoing packets are covered by the checksum and |
| ``self.setsockopt(IPPROTO_UDPLITE, UDPLITE_RECV_CSCOV, length)`` will |
| filter out packets which cover too little of their data. In both cases |
| ``length`` should be in ``range(8, 2**16, 8)``. |
| |
| Such a socket should be constructed with |
| ``socket(AF_INET, SOCK_DGRAM, IPPROTO_UDPLITE)`` for IPv4 or |
| ``socket(AF_INET6, SOCK_DGRAM, IPPROTO_UDPLITE)`` for IPv6. |
| |
| .. availability:: Linux >= 2.6.20, FreeBSD >= 10.1-RELEASE |
| |
| .. versionadded:: 3.9 |
| |
| If you use a hostname in the *host* portion of IPv4/v6 socket address, the |
| program may show a nondeterministic behavior, as Python uses the first address |
| returned from the DNS resolution. The socket address will be resolved |
| differently into an actual IPv4/v6 address, depending on the results from DNS |
| resolution and/or the host configuration. For deterministic behavior use a |
| numeric address in *host* portion. |
| |
| All errors raise exceptions. The normal exceptions for invalid argument types |
| and out-of-memory conditions can be raised; starting from Python 3.3, errors |
| related to socket or address semantics raise :exc:`OSError` or one of its |
| subclasses (they used to raise :exc:`socket.error`). |
| |
| Non-blocking mode is supported through :meth:`~socket.setblocking`. A |
| generalization of this based on timeouts is supported through |
| :meth:`~socket.settimeout`. |
| |
| |
| Module contents |
| --------------- |
| |
| The module :mod:`socket` exports the following elements. |
| |
| |
| Exceptions |
| ^^^^^^^^^^ |
| |
| .. exception:: error |
| |
| A deprecated alias of :exc:`OSError`. |
| |
| .. versionchanged:: 3.3 |
| Following :pep:`3151`, this class was made an alias of :exc:`OSError`. |
| |
| |
| .. exception:: herror |
| |
| A subclass of :exc:`OSError`, this exception is raised for |
| address-related errors, i.e. for functions that use *h_errno* in the POSIX |
| C API, including :func:`gethostbyname_ex` and :func:`gethostbyaddr`. |
| The accompanying value is a pair ``(h_errno, string)`` representing an |
| error returned by a library call. *h_errno* is a numeric value, while |
| *string* represents the description of *h_errno*, as returned by the |
| :c:func:`hstrerror` C function. |
| |
| .. versionchanged:: 3.3 |
| This class was made a subclass of :exc:`OSError`. |
| |
| .. exception:: gaierror |
| |
| A subclass of :exc:`OSError`, this exception is raised for |
| address-related errors by :func:`getaddrinfo` and :func:`getnameinfo`. |
| The accompanying value is a pair ``(error, string)`` representing an error |
| returned by a library call. *string* represents the description of |
| *error*, as returned by the :c:func:`gai_strerror` C function. The |
| numeric *error* value will match one of the :const:`EAI_\*` constants |
| defined in this module. |
| |
| .. versionchanged:: 3.3 |
| This class was made a subclass of :exc:`OSError`. |
| |
| .. exception:: timeout |
| |
| A deprecated alias of :exc:`TimeoutError`. |
| |
| A subclass of :exc:`OSError`, this exception is raised when a timeout |
| occurs on a socket which has had timeouts enabled via a prior call to |
| :meth:`~socket.settimeout` (or implicitly through |
| :func:`~socket.setdefaulttimeout`). The accompanying value is a string |
| whose value is currently always "timed out". |
| |
| .. versionchanged:: 3.3 |
| This class was made a subclass of :exc:`OSError`. |
| |
| .. versionchanged:: 3.10 |
| This class was made an alias of :exc:`TimeoutError`. |
| |
| |
| Constants |
| ^^^^^^^^^ |
| |
| The AF_* and SOCK_* constants are now :class:`AddressFamily` and |
| :class:`SocketKind` :class:`.IntEnum` collections. |
| |
| .. versionadded:: 3.4 |
| |
| .. data:: AF_UNIX |
| AF_INET |
| AF_INET6 |
| |
| These constants represent the address (and protocol) families, used for the |
| first argument to :func:`.socket`. If the :const:`AF_UNIX` constant is not |
| defined then this protocol is unsupported. More constants may be available |
| depending on the system. |
| |
| |
| .. data:: SOCK_STREAM |
| SOCK_DGRAM |
| SOCK_RAW |
| SOCK_RDM |
| SOCK_SEQPACKET |
| |
| These constants represent the socket types, used for the second argument to |
| :func:`.socket`. More constants may be available depending on the system. |
| (Only :const:`SOCK_STREAM` and :const:`SOCK_DGRAM` appear to be generally |
| useful.) |
| |
| .. data:: SOCK_CLOEXEC |
| SOCK_NONBLOCK |
| |
| These two constants, if defined, can be combined with the socket types and |
| allow you to set some flags atomically (thus avoiding possible race |
| conditions and the need for separate calls). |
| |
| .. seealso:: |
| |
| `Secure File Descriptor Handling <http://udrepper.livejournal.com/20407.html>`_ |
| for a more thorough explanation. |
| |
| .. availability:: Linux >= 2.6.27. |
| |
| .. versionadded:: 3.2 |
| |
| .. data:: SO_* |
| SOMAXCONN |
| MSG_* |
| SOL_* |
| SCM_* |
| IPPROTO_* |
| IPPORT_* |
| INADDR_* |
| IP_* |
| IPV6_* |
| EAI_* |
| AI_* |
| NI_* |
| TCP_* |
| |
| Many constants of these forms, documented in the Unix documentation on sockets |
| and/or the IP protocol, are also defined in the socket module. They are |
| generally used in arguments to the :meth:`setsockopt` and :meth:`getsockopt` |
| methods of socket objects. In most cases, only those symbols that are defined |
| in the Unix header files are defined; for a few symbols, default values are |
| provided. |
| |
| .. versionchanged:: 3.6 |
| ``SO_DOMAIN``, ``SO_PROTOCOL``, ``SO_PEERSEC``, ``SO_PASSSEC``, |
| ``TCP_USER_TIMEOUT``, ``TCP_CONGESTION`` were added. |
| |
| .. versionchanged:: 3.6.5 |
| On Windows, ``TCP_FASTOPEN``, ``TCP_KEEPCNT`` appear if run-time Windows |
| supports. |
| |
| .. versionchanged:: 3.7 |
| ``TCP_NOTSENT_LOWAT`` was added. |
| |
| On Windows, ``TCP_KEEPIDLE``, ``TCP_KEEPINTVL`` appear if run-time Windows |
| supports. |
| |
| .. data:: AF_CAN |
| PF_CAN |
| SOL_CAN_* |
| CAN_* |
| |
| Many constants of these forms, documented in the Linux documentation, are |
| also defined in the socket module. |
| |
| .. availability:: Linux >= 2.6.25. |
| |
| .. versionadded:: 3.3 |
| |
| .. data:: CAN_BCM |
| CAN_BCM_* |
| |
| CAN_BCM, in the CAN protocol family, is the broadcast manager (BCM) protocol. |
| Broadcast manager constants, documented in the Linux documentation, are also |
| defined in the socket module. |
| |
| .. availability:: Linux >= 2.6.25. |
| |
| .. note:: |
| The :data:`CAN_BCM_CAN_FD_FRAME` flag is only available on Linux >= 4.8. |
| |
| .. versionadded:: 3.4 |
| |
| .. data:: CAN_RAW_FD_FRAMES |
| |
| Enables CAN FD support in a CAN_RAW socket. This is disabled by default. |
| This allows your application to send both CAN and CAN FD frames; however, |
| you must accept both CAN and CAN FD frames when reading from the socket. |
| |
| This constant is documented in the Linux documentation. |
| |
| .. availability:: Linux >= 3.6. |
| |
| .. versionadded:: 3.5 |
| |
| .. data:: CAN_RAW_JOIN_FILTERS |
| |
| Joins the applied CAN filters such that only CAN frames that match all |
| given CAN filters are passed to user space. |
| |
| This constant is documented in the Linux documentation. |
| |
| .. availability:: Linux >= 4.1. |
| |
| .. versionadded:: 3.9 |
| |
| .. data:: CAN_ISOTP |
| |
| CAN_ISOTP, in the CAN protocol family, is the ISO-TP (ISO 15765-2) protocol. |
| ISO-TP constants, documented in the Linux documentation. |
| |
| .. availability:: Linux >= 2.6.25. |
| |
| .. versionadded:: 3.7 |
| |
| .. data:: CAN_J1939 |
| |
| CAN_J1939, in the CAN protocol family, is the SAE J1939 protocol. |
| J1939 constants, documented in the Linux documentation. |
| |
| .. availability:: Linux >= 5.4. |
| |
| .. versionadded:: 3.9 |
| |
| |
| .. data:: AF_PACKET |
| PF_PACKET |
| PACKET_* |
| |
| Many constants of these forms, documented in the Linux documentation, are |
| also defined in the socket module. |
| |
| .. availability:: Linux >= 2.2. |
| |
| |
| .. data:: AF_RDS |
| PF_RDS |
| SOL_RDS |
| RDS_* |
| |
| Many constants of these forms, documented in the Linux documentation, are |
| also defined in the socket module. |
| |
| .. availability:: Linux >= 2.6.30. |
| |
| .. versionadded:: 3.3 |
| |
| |
| .. data:: SIO_RCVALL |
| SIO_KEEPALIVE_VALS |
| SIO_LOOPBACK_FAST_PATH |
| RCVALL_* |
| |
| Constants for Windows' WSAIoctl(). The constants are used as arguments to the |
| :meth:`~socket.socket.ioctl` method of socket objects. |
| |
| .. versionchanged:: 3.6 |
| ``SIO_LOOPBACK_FAST_PATH`` was added. |
| |
| |
| .. data:: TIPC_* |
| |
| TIPC related constants, matching the ones exported by the C socket API. See |
| the TIPC documentation for more information. |
| |
| .. data:: AF_ALG |
| SOL_ALG |
| ALG_* |
| |
| Constants for Linux Kernel cryptography. |
| |
| .. availability:: Linux >= 2.6.38. |
| |
| .. versionadded:: 3.6 |
| |
| |
| .. data:: AF_VSOCK |
| IOCTL_VM_SOCKETS_GET_LOCAL_CID |
| VMADDR* |
| SO_VM* |
| |
| Constants for Linux host/guest communication. |
| |
| .. availability:: Linux >= 4.8. |
| |
| .. versionadded:: 3.7 |
| |
| .. data:: AF_LINK |
| |
| .. availability:: BSD, OSX. |
| |
| .. versionadded:: 3.4 |
| |
| .. data:: has_ipv6 |
| |
| This constant contains a boolean value which indicates if IPv6 is supported on |
| this platform. |
| |
| .. data:: BDADDR_ANY |
| BDADDR_LOCAL |
| |
| These are string constants containing Bluetooth addresses with special |
| meanings. For example, :const:`BDADDR_ANY` can be used to indicate |
| any address when specifying the binding socket with |
| :const:`BTPROTO_RFCOMM`. |
| |
| .. data:: HCI_FILTER |
| HCI_TIME_STAMP |
| HCI_DATA_DIR |
| |
| For use with :const:`BTPROTO_HCI`. :const:`HCI_FILTER` is not |
| available for NetBSD or DragonFlyBSD. :const:`HCI_TIME_STAMP` and |
| :const:`HCI_DATA_DIR` are not available for FreeBSD, NetBSD, or |
| DragonFlyBSD. |
| |
| .. data:: AF_QIPCRTR |
| |
| Constant for Qualcomm's IPC router protocol, used to communicate with |
| service providing remote processors. |
| |
| .. availability:: Linux >= 4.7. |
| |
| Functions |
| ^^^^^^^^^ |
| |
| Creating sockets |
| '''''''''''''''' |
| |
| The following functions all create :ref:`socket objects <socket-objects>`. |
| |
| |
| .. function:: socket(family=AF_INET, type=SOCK_STREAM, proto=0, fileno=None) |
| |
| Create a new socket using the given address family, socket type and protocol |
| number. The address family should be :const:`AF_INET` (the default), |
| :const:`AF_INET6`, :const:`AF_UNIX`, :const:`AF_CAN`, :const:`AF_PACKET`, |
| or :const:`AF_RDS`. The socket type should be :const:`SOCK_STREAM` (the |
| default), :const:`SOCK_DGRAM`, :const:`SOCK_RAW` or perhaps one of the other |
| ``SOCK_`` constants. The protocol number is usually zero and may be omitted |
| or in the case where the address family is :const:`AF_CAN` the protocol |
| should be one of :const:`CAN_RAW`, :const:`CAN_BCM`, :const:`CAN_ISOTP` or |
| :const:`CAN_J1939`. |
| |
| If *fileno* is specified, the values for *family*, *type*, and *proto* are |
| auto-detected from the specified file descriptor. Auto-detection can be |
| overruled by calling the function with explicit *family*, *type*, or *proto* |
| arguments. This only affects how Python represents e.g. the return value |
| of :meth:`socket.getpeername` but not the actual OS resource. Unlike |
| :func:`socket.fromfd`, *fileno* will return the same socket and not a |
| duplicate. This may help close a detached socket using |
| :meth:`socket.close()`. |
| |
| The newly created socket is :ref:`non-inheritable <fd_inheritance>`. |
| |
| .. audit-event:: socket.__new__ self,family,type,protocol socket.socket |
| |
| .. versionchanged:: 3.3 |
| The AF_CAN family was added. |
| The AF_RDS family was added. |
| |
| .. versionchanged:: 3.4 |
| The CAN_BCM protocol was added. |
| |
| .. versionchanged:: 3.4 |
| The returned socket is now non-inheritable. |
| |
| .. versionchanged:: 3.7 |
| The CAN_ISOTP protocol was added. |
| |
| .. versionchanged:: 3.7 |
| When :const:`SOCK_NONBLOCK` or :const:`SOCK_CLOEXEC` |
| bit flags are applied to *type* they are cleared, and |
| :attr:`socket.type` will not reflect them. They are still passed |
| to the underlying system `socket()` call. Therefore, |
| |
| :: |
| |
| sock = socket.socket( |
| socket.AF_INET, |
| socket.SOCK_STREAM | socket.SOCK_NONBLOCK) |
| |
| will still create a non-blocking socket on OSes that support |
| ``SOCK_NONBLOCK``, but ``sock.type`` will be set to |
| ``socket.SOCK_STREAM``. |
| |
| .. versionchanged:: 3.9 |
| The CAN_J1939 protocol was added. |
| |
| .. function:: socketpair([family[, type[, proto]]]) |
| |
| Build a pair of connected socket objects using the given address family, socket |
| type, and protocol number. Address family, socket type, and protocol number are |
| as for the :func:`.socket` function above. The default family is :const:`AF_UNIX` |
| if defined on the platform; otherwise, the default is :const:`AF_INET`. |
| |
| The newly created sockets are :ref:`non-inheritable <fd_inheritance>`. |
| |
| .. versionchanged:: 3.2 |
| The returned socket objects now support the whole socket API, rather |
| than a subset. |
| |
| .. versionchanged:: 3.4 |
| The returned sockets are now non-inheritable. |
| |
| .. versionchanged:: 3.5 |
| Windows support added. |
| |
| |
| .. function:: create_connection(address[, timeout[, source_address]]) |
| |
| Connect to a TCP service listening on the Internet *address* (a 2-tuple |
| ``(host, port)``), and return the socket object. This is a higher-level |
| function than :meth:`socket.connect`: if *host* is a non-numeric hostname, |
| it will try to resolve it for both :data:`AF_INET` and :data:`AF_INET6`, |
| and then try to connect to all possible addresses in turn until a |
| connection succeeds. This makes it easy to write clients that are |
| compatible to both IPv4 and IPv6. |
| |
| Passing the optional *timeout* parameter will set the timeout on the |
| socket instance before attempting to connect. If no *timeout* is |
| supplied, the global default timeout setting returned by |
| :func:`getdefaulttimeout` is used. |
| |
| If supplied, *source_address* must be a 2-tuple ``(host, port)`` for the |
| socket to bind to as its source address before connecting. If host or port |
| are '' or 0 respectively the OS default behavior will be used. |
| |
| .. versionchanged:: 3.2 |
| *source_address* was added. |
| |
| .. function:: create_server(address, *, family=AF_INET, backlog=None, reuse_port=False, dualstack_ipv6=False) |
| |
| Convenience function which creates a TCP socket bound to *address* (a 2-tuple |
| ``(host, port)``) and return the socket object. |
| |
| *family* should be either :data:`AF_INET` or :data:`AF_INET6`. |
| *backlog* is the queue size passed to :meth:`socket.listen`; when ``0`` |
| a default reasonable value is chosen. |
| *reuse_port* dictates whether to set the :data:`SO_REUSEPORT` socket option. |
| |
| If *dualstack_ipv6* is true and the platform supports it the socket will |
| be able to accept both IPv4 and IPv6 connections, else it will raise |
| :exc:`ValueError`. Most POSIX platforms and Windows are supposed to support |
| this functionality. |
| When this functionality is enabled the address returned by |
| :meth:`socket.getpeername` when an IPv4 connection occurs will be an IPv6 |
| address represented as an IPv4-mapped IPv6 address. |
| If *dualstack_ipv6* is false it will explicitly disable this functionality |
| on platforms that enable it by default (e.g. Linux). |
| This parameter can be used in conjunction with :func:`has_dualstack_ipv6`: |
| |
| :: |
| |
| import socket |
| |
| addr = ("", 8080) # all interfaces, port 8080 |
| if socket.has_dualstack_ipv6(): |
| s = socket.create_server(addr, family=socket.AF_INET6, dualstack_ipv6=True) |
| else: |
| s = socket.create_server(addr) |
| |
| .. note:: |
| On POSIX platforms the :data:`SO_REUSEADDR` socket option is set in order to |
| immediately reuse previous sockets which were bound on the same *address* |
| and remained in TIME_WAIT state. |
| |
| .. versionadded:: 3.8 |
| |
| .. function:: has_dualstack_ipv6() |
| |
| Return ``True`` if the platform supports creating a TCP socket which can |
| handle both IPv4 and IPv6 connections. |
| |
| .. versionadded:: 3.8 |
| |
| .. function:: fromfd(fd, family, type, proto=0) |
| |
| Duplicate the file descriptor *fd* (an integer as returned by a file object's |
| :meth:`fileno` method) and build a socket object from the result. Address |
| family, socket type and protocol number are as for the :func:`.socket` function |
| above. The file descriptor should refer to a socket, but this is not checked --- |
| subsequent operations on the object may fail if the file descriptor is invalid. |
| This function is rarely needed, but can be used to get or set socket options on |
| a socket passed to a program as standard input or output (such as a server |
| started by the Unix inet daemon). The socket is assumed to be in blocking mode. |
| |
| The newly created socket is :ref:`non-inheritable <fd_inheritance>`. |
| |
| .. versionchanged:: 3.4 |
| The returned socket is now non-inheritable. |
| |
| |
| .. function:: fromshare(data) |
| |
| Instantiate a socket from data obtained from the :meth:`socket.share` |
| method. The socket is assumed to be in blocking mode. |
| |
| .. availability:: Windows. |
| |
| .. versionadded:: 3.3 |
| |
| |
| .. data:: SocketType |
| |
| This is a Python type object that represents the socket object type. It is the |
| same as ``type(socket(...))``. |
| |
| |
| Other functions |
| ''''''''''''''' |
| |
| The :mod:`socket` module also offers various network-related services: |
| |
| |
| .. function:: close(fd) |
| |
| Close a socket file descriptor. This is like :func:`os.close`, but for |
| sockets. On some platforms (most noticeable Windows) :func:`os.close` |
| does not work for socket file descriptors. |
| |
| .. versionadded:: 3.7 |
| |
| .. function:: getaddrinfo(host, port, family=0, type=0, proto=0, flags=0) |
| |
| Translate the *host*/*port* argument into a sequence of 5-tuples that contain |
| all the necessary arguments for creating a socket connected to that service. |
| *host* is a domain name, a string representation of an IPv4/v6 address |
| or ``None``. *port* is a string service name such as ``'http'``, a numeric |
| port number or ``None``. By passing ``None`` as the value of *host* |
| and *port*, you can pass ``NULL`` to the underlying C API. |
| |
| The *family*, *type* and *proto* arguments can be optionally specified |
| in order to narrow the list of addresses returned. Passing zero as a |
| value for each of these arguments selects the full range of results. |
| The *flags* argument can be one or several of the ``AI_*`` constants, |
| and will influence how results are computed and returned. |
| For example, :const:`AI_NUMERICHOST` will disable domain name resolution |
| and will raise an error if *host* is a domain name. |
| |
| The function returns a list of 5-tuples with the following structure: |
| |
| ``(family, type, proto, canonname, sockaddr)`` |
| |
| In these tuples, *family*, *type*, *proto* are all integers and are |
| meant to be passed to the :func:`.socket` function. *canonname* will be |
| a string representing the canonical name of the *host* if |
| :const:`AI_CANONNAME` is part of the *flags* argument; else *canonname* |
| will be empty. *sockaddr* is a tuple describing a socket address, whose |
| format depends on the returned *family* (a ``(address, port)`` 2-tuple for |
| :const:`AF_INET`, a ``(address, port, flowinfo, scope_id)`` 4-tuple for |
| :const:`AF_INET6`), and is meant to be passed to the :meth:`socket.connect` |
| method. |
| |
| .. audit-event:: socket.getaddrinfo host,port,family,type,protocol socket.getaddrinfo |
| |
| The following example fetches address information for a hypothetical TCP |
| connection to ``example.org`` on port 80 (results may differ on your |
| system if IPv6 isn't enabled):: |
| |
| >>> socket.getaddrinfo("example.org", 80, proto=socket.IPPROTO_TCP) |
| [(<AddressFamily.AF_INET6: 10>, <SocketType.SOCK_STREAM: 1>, |
| 6, '', ('2606:2800:220:1:248:1893:25c8:1946', 80, 0, 0)), |
| (<AddressFamily.AF_INET: 2>, <SocketType.SOCK_STREAM: 1>, |
| 6, '', ('93.184.216.34', 80))] |
| |
| .. versionchanged:: 3.2 |
| parameters can now be passed using keyword arguments. |
| |
| .. versionchanged:: 3.7 |
| for IPv6 multicast addresses, string representing an address will not |
| contain ``%scope_id`` part. |
| |
| .. function:: getfqdn([name]) |
| |
| Return a fully qualified domain name for *name*. If *name* is omitted or empty, |
| it is interpreted as the local host. To find the fully qualified name, the |
| hostname returned by :func:`gethostbyaddr` is checked, followed by aliases for the |
| host, if available. The first name which includes a period is selected. In |
| case no fully qualified domain name is available, the hostname as returned by |
| :func:`gethostname` is returned. |
| |
| |
| .. function:: gethostbyname(hostname) |
| |
| Translate a host name to IPv4 address format. The IPv4 address is returned as a |
| string, such as ``'100.50.200.5'``. If the host name is an IPv4 address itself |
| it is returned unchanged. See :func:`gethostbyname_ex` for a more complete |
| interface. :func:`gethostbyname` does not support IPv6 name resolution, and |
| :func:`getaddrinfo` should be used instead for IPv4/v6 dual stack support. |
| |
| .. audit-event:: socket.gethostbyname hostname socket.gethostbyname |
| |
| |
| .. function:: gethostbyname_ex(hostname) |
| |
| Translate a host name to IPv4 address format, extended interface. Return a |
| triple ``(hostname, aliaslist, ipaddrlist)`` where *hostname* is the primary |
| host name responding to the given *ip_address*, *aliaslist* is a (possibly |
| empty) list of alternative host names for the same address, and *ipaddrlist* is |
| a list of IPv4 addresses for the same interface on the same host (often but not |
| always a single address). :func:`gethostbyname_ex` does not support IPv6 name |
| resolution, and :func:`getaddrinfo` should be used instead for IPv4/v6 dual |
| stack support. |
| |
| .. audit-event:: socket.gethostbyname hostname socket.gethostbyname_ex |
| |
| |
| .. function:: gethostname() |
| |
| Return a string containing the hostname of the machine where the Python |
| interpreter is currently executing. |
| |
| .. audit-event:: socket.gethostname "" socket.gethostname |
| |
| Note: :func:`gethostname` doesn't always return the fully qualified domain |
| name; use :func:`getfqdn` for that. |
| |
| |
| .. function:: gethostbyaddr(ip_address) |
| |
| Return a triple ``(hostname, aliaslist, ipaddrlist)`` where *hostname* is the |
| primary host name responding to the given *ip_address*, *aliaslist* is a |
| (possibly empty) list of alternative host names for the same address, and |
| *ipaddrlist* is a list of IPv4/v6 addresses for the same interface on the same |
| host (most likely containing only a single address). To find the fully qualified |
| domain name, use the function :func:`getfqdn`. :func:`gethostbyaddr` supports |
| both IPv4 and IPv6. |
| |
| .. audit-event:: socket.gethostbyaddr ip_address socket.gethostbyaddr |
| |
| |
| .. function:: getnameinfo(sockaddr, flags) |
| |
| Translate a socket address *sockaddr* into a 2-tuple ``(host, port)``. Depending |
| on the settings of *flags*, the result can contain a fully-qualified domain name |
| or numeric address representation in *host*. Similarly, *port* can contain a |
| string port name or a numeric port number. |
| |
| For IPv6 addresses, ``%scope_id`` is appended to the host part if *sockaddr* |
| contains meaningful *scope_id*. Usually this happens for multicast addresses. |
| |
| For more information about *flags* you can consult :manpage:`getnameinfo(3)`. |
| |
| .. audit-event:: socket.getnameinfo sockaddr socket.getnameinfo |
| |
| .. function:: getprotobyname(protocolname) |
| |
| Translate an Internet protocol name (for example, ``'icmp'``) to a constant |
| suitable for passing as the (optional) third argument to the :func:`.socket` |
| function. This is usually only needed for sockets opened in "raw" mode |
| (:const:`SOCK_RAW`); for the normal socket modes, the correct protocol is chosen |
| automatically if the protocol is omitted or zero. |
| |
| |
| .. function:: getservbyname(servicename[, protocolname]) |
| |
| Translate an Internet service name and protocol name to a port number for that |
| service. The optional protocol name, if given, should be ``'tcp'`` or |
| ``'udp'``, otherwise any protocol will match. |
| |
| .. audit-event:: socket.getservbyname servicename,protocolname socket.getservbyname |
| |
| |
| .. function:: getservbyport(port[, protocolname]) |
| |
| Translate an Internet port number and protocol name to a service name for that |
| service. The optional protocol name, if given, should be ``'tcp'`` or |
| ``'udp'``, otherwise any protocol will match. |
| |
| .. audit-event:: socket.getservbyport port,protocolname socket.getservbyport |
| |
| |
| .. function:: ntohl(x) |
| |
| Convert 32-bit positive integers from network to host byte order. On machines |
| where the host byte order is the same as network byte order, this is a no-op; |
| otherwise, it performs a 4-byte swap operation. |
| |
| |
| .. function:: ntohs(x) |
| |
| Convert 16-bit positive integers from network to host byte order. On machines |
| where the host byte order is the same as network byte order, this is a no-op; |
| otherwise, it performs a 2-byte swap operation. |
| |
| .. deprecated:: 3.7 |
| In case *x* does not fit in 16-bit unsigned integer, but does fit in a |
| positive C int, it is silently truncated to 16-bit unsigned integer. |
| This silent truncation feature is deprecated, and will raise an |
| exception in future versions of Python. |
| |
| |
| .. function:: htonl(x) |
| |
| Convert 32-bit positive integers from host to network byte order. On machines |
| where the host byte order is the same as network byte order, this is a no-op; |
| otherwise, it performs a 4-byte swap operation. |
| |
| |
| .. function:: htons(x) |
| |
| Convert 16-bit positive integers from host to network byte order. On machines |
| where the host byte order is the same as network byte order, this is a no-op; |
| otherwise, it performs a 2-byte swap operation. |
| |
| .. deprecated:: 3.7 |
| In case *x* does not fit in 16-bit unsigned integer, but does fit in a |
| positive C int, it is silently truncated to 16-bit unsigned integer. |
| This silent truncation feature is deprecated, and will raise an |
| exception in future versions of Python. |
| |
| |
| .. function:: inet_aton(ip_string) |
| |
| Convert an IPv4 address from dotted-quad string format (for example, |
| '123.45.67.89') to 32-bit packed binary format, as a bytes object four characters in |
| length. This is useful when conversing with a program that uses the standard C |
| library and needs objects of type :c:type:`struct in_addr`, which is the C type |
| for the 32-bit packed binary this function returns. |
| |
| :func:`inet_aton` also accepts strings with less than three dots; see the |
| Unix manual page :manpage:`inet(3)` for details. |
| |
| If the IPv4 address string passed to this function is invalid, |
| :exc:`OSError` will be raised. Note that exactly what is valid depends on |
| the underlying C implementation of :c:func:`inet_aton`. |
| |
| :func:`inet_aton` does not support IPv6, and :func:`inet_pton` should be used |
| instead for IPv4/v6 dual stack support. |
| |
| |
| .. function:: inet_ntoa(packed_ip) |
| |
| Convert a 32-bit packed IPv4 address (a :term:`bytes-like object` four |
| bytes in length) to its standard dotted-quad string representation (for example, |
| '123.45.67.89'). This is useful when conversing with a program that uses the |
| standard C library and needs objects of type :c:type:`struct in_addr`, which |
| is the C type for the 32-bit packed binary data this function takes as an |
| argument. |
| |
| If the byte sequence passed to this function is not exactly 4 bytes in |
| length, :exc:`OSError` will be raised. :func:`inet_ntoa` does not |
| support IPv6, and :func:`inet_ntop` should be used instead for IPv4/v6 dual |
| stack support. |
| |
| .. versionchanged:: 3.5 |
| Writable :term:`bytes-like object` is now accepted. |
| |
| |
| .. function:: inet_pton(address_family, ip_string) |
| |
| Convert an IP address from its family-specific string format to a packed, |
| binary format. :func:`inet_pton` is useful when a library or network protocol |
| calls for an object of type :c:type:`struct in_addr` (similar to |
| :func:`inet_aton`) or :c:type:`struct in6_addr`. |
| |
| Supported values for *address_family* are currently :const:`AF_INET` and |
| :const:`AF_INET6`. If the IP address string *ip_string* is invalid, |
| :exc:`OSError` will be raised. Note that exactly what is valid depends on |
| both the value of *address_family* and the underlying implementation of |
| :c:func:`inet_pton`. |
| |
| .. availability:: Unix (maybe not all platforms), Windows. |
| |
| .. versionchanged:: 3.4 |
| Windows support added |
| |
| |
| .. function:: inet_ntop(address_family, packed_ip) |
| |
| Convert a packed IP address (a :term:`bytes-like object` of some number of |
| bytes) to its standard, family-specific string representation (for |
| example, ``'7.10.0.5'`` or ``'5aef:2b::8'``). |
| :func:`inet_ntop` is useful when a library or network protocol returns an |
| object of type :c:type:`struct in_addr` (similar to :func:`inet_ntoa`) or |
| :c:type:`struct in6_addr`. |
| |
| Supported values for *address_family* are currently :const:`AF_INET` and |
| :const:`AF_INET6`. If the bytes object *packed_ip* is not the correct |
| length for the specified address family, :exc:`ValueError` will be raised. |
| :exc:`OSError` is raised for errors from the call to :func:`inet_ntop`. |
| |
| .. availability:: Unix (maybe not all platforms), Windows. |
| |
| .. versionchanged:: 3.4 |
| Windows support added |
| |
| .. versionchanged:: 3.5 |
| Writable :term:`bytes-like object` is now accepted. |
| |
| |
| .. |
| XXX: Are sendmsg(), recvmsg() and CMSG_*() available on any |
| non-Unix platforms? The old (obsolete?) 4.2BSD form of the |
| interface, in which struct msghdr has no msg_control or |
| msg_controllen members, is not currently supported. |
| |
| .. function:: CMSG_LEN(length) |
| |
| Return the total length, without trailing padding, of an ancillary |
| data item with associated data of the given *length*. This value |
| can often be used as the buffer size for :meth:`~socket.recvmsg` to |
| receive a single item of ancillary data, but :rfc:`3542` requires |
| portable applications to use :func:`CMSG_SPACE` and thus include |
| space for padding, even when the item will be the last in the |
| buffer. Raises :exc:`OverflowError` if *length* is outside the |
| permissible range of values. |
| |
| .. availability:: most Unix platforms, possibly others. |
| |
| .. versionadded:: 3.3 |
| |
| |
| .. function:: CMSG_SPACE(length) |
| |
| Return the buffer size needed for :meth:`~socket.recvmsg` to |
| receive an ancillary data item with associated data of the given |
| *length*, along with any trailing padding. The buffer space needed |
| to receive multiple items is the sum of the :func:`CMSG_SPACE` |
| values for their associated data lengths. Raises |
| :exc:`OverflowError` if *length* is outside the permissible range |
| of values. |
| |
| Note that some systems might support ancillary data without |
| providing this function. Also note that setting the buffer size |
| using the results of this function may not precisely limit the |
| amount of ancillary data that can be received, since additional |
| data may be able to fit into the padding area. |
| |
| .. availability:: most Unix platforms, possibly others. |
| |
| .. versionadded:: 3.3 |
| |
| |
| .. function:: getdefaulttimeout() |
| |
| Return the default timeout in seconds (float) for new socket objects. A value |
| of ``None`` indicates that new socket objects have no timeout. When the socket |
| module is first imported, the default is ``None``. |
| |
| |
| .. function:: setdefaulttimeout(timeout) |
| |
| Set the default timeout in seconds (float) for new socket objects. When |
| the socket module is first imported, the default is ``None``. See |
| :meth:`~socket.settimeout` for possible values and their respective |
| meanings. |
| |
| |
| .. function:: sethostname(name) |
| |
| Set the machine's hostname to *name*. This will raise an |
| :exc:`OSError` if you don't have enough rights. |
| |
| .. audit-event:: socket.sethostname name socket.sethostname |
| |
| .. availability:: Unix. |
| |
| .. versionadded:: 3.3 |
| |
| |
| .. function:: if_nameindex() |
| |
| Return a list of network interface information |
| (index int, name string) tuples. |
| :exc:`OSError` if the system call fails. |
| |
| .. availability:: Unix, Windows. |
| |
| .. versionadded:: 3.3 |
| |
| .. versionchanged:: 3.8 |
| Windows support was added. |
| |
| .. note:: |
| |
| On Windows network interfaces have different names in different contexts |
| (all names are examples): |
| |
| * UUID: ``{FB605B73-AAC2-49A6-9A2F-25416AEA0573}`` |
| * name: ``ethernet_32770`` |
| * friendly name: ``vEthernet (nat)`` |
| * description: ``Hyper-V Virtual Ethernet Adapter`` |
| |
| This function returns names of the second form from the list, ``ethernet_32770`` |
| in this example case. |
| |
| |
| .. function:: if_nametoindex(if_name) |
| |
| Return a network interface index number corresponding to an |
| interface name. |
| :exc:`OSError` if no interface with the given name exists. |
| |
| .. availability:: Unix, Windows. |
| |
| .. versionadded:: 3.3 |
| |
| .. versionchanged:: 3.8 |
| Windows support was added. |
| |
| .. seealso:: |
| "Interface name" is a name as documented in :func:`if_nameindex`. |
| |
| |
| .. function:: if_indextoname(if_index) |
| |
| Return a network interface name corresponding to an |
| interface index number. |
| :exc:`OSError` if no interface with the given index exists. |
| |
| .. availability:: Unix, Windows. |
| |
| .. versionadded:: 3.3 |
| |
| .. versionchanged:: 3.8 |
| Windows support was added. |
| |
| .. seealso:: |
| "Interface name" is a name as documented in :func:`if_nameindex`. |
| |
| |
| .. _socket-objects: |
| |
| Socket Objects |
| -------------- |
| |
| Socket objects have the following methods. Except for |
| :meth:`~socket.makefile`, these correspond to Unix system calls applicable |
| to sockets. |
| |
| .. versionchanged:: 3.2 |
| Support for the :term:`context manager` protocol was added. Exiting the |
| context manager is equivalent to calling :meth:`~socket.close`. |
| |
| |
| .. method:: socket.accept() |
| |
| Accept a connection. The socket must be bound to an address and listening for |
| connections. The return value is a pair ``(conn, address)`` where *conn* is a |
| *new* socket object usable to send and receive data on the connection, and |
| *address* is the address bound to the socket on the other end of the connection. |
| |
| The newly created socket is :ref:`non-inheritable <fd_inheritance>`. |
| |
| .. versionchanged:: 3.4 |
| The socket is now non-inheritable. |
| |
| .. versionchanged:: 3.5 |
| If the system call is interrupted and the signal handler does not raise |
| an exception, the method now retries the system call instead of raising |
| an :exc:`InterruptedError` exception (see :pep:`475` for the rationale). |
| |
| |
| .. method:: socket.bind(address) |
| |
| Bind the socket to *address*. The socket must not already be bound. (The format |
| of *address* depends on the address family --- see above.) |
| |
| .. audit-event:: socket.bind self,address socket.socket.bind |
| |
| .. method:: socket.close() |
| |
| Mark the socket closed. The underlying system resource (e.g. a file |
| descriptor) is also closed when all file objects from :meth:`makefile()` |
| are closed. Once that happens, all future operations on the socket |
| object will fail. The remote end will receive no more data (after |
| queued data is flushed). |
| |
| Sockets are automatically closed when they are garbage-collected, but |
| it is recommended to :meth:`close` them explicitly, or to use a |
| :keyword:`with` statement around them. |
| |
| .. versionchanged:: 3.6 |
| :exc:`OSError` is now raised if an error occurs when the underlying |
| :c:func:`close` call is made. |
| |
| .. note:: |
| |
| :meth:`close()` releases the resource associated with a connection but |
| does not necessarily close the connection immediately. If you want |
| to close the connection in a timely fashion, call :meth:`shutdown()` |
| before :meth:`close()`. |
| |
| |
| .. method:: socket.connect(address) |
| |
| Connect to a remote socket at *address*. (The format of *address* depends on the |
| address family --- see above.) |
| |
| If the connection is interrupted by a signal, the method waits until the |
| connection completes, or raise a :exc:`TimeoutError` on timeout, if the |
| signal handler doesn't raise an exception and the socket is blocking or has |
| a timeout. For non-blocking sockets, the method raises an |
| :exc:`InterruptedError` exception if the connection is interrupted by a |
| signal (or the exception raised by the signal handler). |
| |
| .. audit-event:: socket.connect self,address socket.socket.connect |
| |
| .. versionchanged:: 3.5 |
| The method now waits until the connection completes instead of raising an |
| :exc:`InterruptedError` exception if the connection is interrupted by a |
| signal, the signal handler doesn't raise an exception and the socket is |
| blocking or has a timeout (see the :pep:`475` for the rationale). |
| |
| |
| .. method:: socket.connect_ex(address) |
| |
| Like ``connect(address)``, but return an error indicator instead of raising an |
| exception for errors returned by the C-level :c:func:`connect` call (other |
| problems, such as "host not found," can still raise exceptions). The error |
| indicator is ``0`` if the operation succeeded, otherwise the value of the |
| :c:data:`errno` variable. This is useful to support, for example, asynchronous |
| connects. |
| |
| .. audit-event:: socket.connect self,address socket.socket.connect_ex |
| |
| .. method:: socket.detach() |
| |
| Put the socket object into closed state without actually closing the |
| underlying file descriptor. The file descriptor is returned, and can |
| be reused for other purposes. |
| |
| .. versionadded:: 3.2 |
| |
| |
| .. method:: socket.dup() |
| |
| Duplicate the socket. |
| |
| The newly created socket is :ref:`non-inheritable <fd_inheritance>`. |
| |
| .. versionchanged:: 3.4 |
| The socket is now non-inheritable. |
| |
| |
| .. method:: socket.fileno() |
| |
| Return the socket's file descriptor (a small integer), or -1 on failure. This |
| is useful with :func:`select.select`. |
| |
| Under Windows the small integer returned by this method cannot be used where a |
| file descriptor can be used (such as :func:`os.fdopen`). Unix does not have |
| this limitation. |
| |
| .. method:: socket.get_inheritable() |
| |
| Get the :ref:`inheritable flag <fd_inheritance>` of the socket's file |
| descriptor or socket's handle: ``True`` if the socket can be inherited in |
| child processes, ``False`` if it cannot. |
| |
| .. versionadded:: 3.4 |
| |
| |
| .. method:: socket.getpeername() |
| |
| Return the remote address to which the socket is connected. This is useful to |
| find out the port number of a remote IPv4/v6 socket, for instance. (The format |
| of the address returned depends on the address family --- see above.) On some |
| systems this function is not supported. |
| |
| |
| .. method:: socket.getsockname() |
| |
| Return the socket's own address. This is useful to find out the port number of |
| an IPv4/v6 socket, for instance. (The format of the address returned depends on |
| the address family --- see above.) |
| |
| |
| .. method:: socket.getsockopt(level, optname[, buflen]) |
| |
| Return the value of the given socket option (see the Unix man page |
| :manpage:`getsockopt(2)`). The needed symbolic constants (:const:`SO_\*` etc.) |
| are defined in this module. If *buflen* is absent, an integer option is assumed |
| and its integer value is returned by the function. If *buflen* is present, it |
| specifies the maximum length of the buffer used to receive the option in, and |
| this buffer is returned as a bytes object. It is up to the caller to decode the |
| contents of the buffer (see the optional built-in module :mod:`struct` for a way |
| to decode C structures encoded as byte strings). |
| |
| |
| .. method:: socket.getblocking() |
| |
| Return ``True`` if socket is in blocking mode, ``False`` if in |
| non-blocking. |
| |
| This is equivalent to checking ``socket.gettimeout() == 0``. |
| |
| .. versionadded:: 3.7 |
| |
| |
| .. method:: socket.gettimeout() |
| |
| Return the timeout in seconds (float) associated with socket operations, |
| or ``None`` if no timeout is set. This reflects the last call to |
| :meth:`setblocking` or :meth:`settimeout`. |
| |
| |
| .. method:: socket.ioctl(control, option) |
| |
| :platform: Windows |
| |
| The :meth:`ioctl` method is a limited interface to the WSAIoctl system |
| interface. Please refer to the `Win32 documentation |
| <https://msdn.microsoft.com/en-us/library/ms741621%28VS.85%29.aspx>`_ for more |
| information. |
| |
| On other platforms, the generic :func:`fcntl.fcntl` and :func:`fcntl.ioctl` |
| functions may be used; they accept a socket object as their first argument. |
| |
| Currently only the following control codes are supported: |
| ``SIO_RCVALL``, ``SIO_KEEPALIVE_VALS``, and ``SIO_LOOPBACK_FAST_PATH``. |
| |
| .. versionchanged:: 3.6 |
| ``SIO_LOOPBACK_FAST_PATH`` was added. |
| |
| .. method:: socket.listen([backlog]) |
| |
| Enable a server to accept connections. If *backlog* is specified, it must |
| be at least 0 (if it is lower, it is set to 0); it specifies the number of |
| unaccepted connections that the system will allow before refusing new |
| connections. If not specified, a default reasonable value is chosen. |
| |
| .. versionchanged:: 3.5 |
| The *backlog* parameter is now optional. |
| |
| .. method:: socket.makefile(mode='r', buffering=None, *, encoding=None, \ |
| errors=None, newline=None) |
| |
| .. index:: single: I/O control; buffering |
| |
| Return a :term:`file object` associated with the socket. The exact returned |
| type depends on the arguments given to :meth:`makefile`. These arguments are |
| interpreted the same way as by the built-in :func:`open` function, except |
| the only supported *mode* values are ``'r'`` (default), ``'w'`` and ``'b'``. |
| |
| The socket must be in blocking mode; it can have a timeout, but the file |
| object's internal buffer may end up in an inconsistent state if a timeout |
| occurs. |
| |
| Closing the file object returned by :meth:`makefile` won't close the |
| original socket unless all other file objects have been closed and |
| :meth:`socket.close` has been called on the socket object. |
| |
| .. note:: |
| |
| On Windows, the file-like object created by :meth:`makefile` cannot be |
| used where a file object with a file descriptor is expected, such as the |
| stream arguments of :meth:`subprocess.Popen`. |
| |
| |
| .. method:: socket.recv(bufsize[, flags]) |
| |
| Receive data from the socket. The return value is a bytes object representing the |
| data received. The maximum amount of data to be received at once is specified |
| by *bufsize*. See the Unix manual page :manpage:`recv(2)` for the meaning of |
| the optional argument *flags*; it defaults to zero. |
| |
| .. note:: |
| |
| For best match with hardware and network realities, the value of *bufsize* |
| should be a relatively small power of 2, for example, 4096. |
| |
| .. versionchanged:: 3.5 |
| If the system call is interrupted and the signal handler does not raise |
| an exception, the method now retries the system call instead of raising |
| an :exc:`InterruptedError` exception (see :pep:`475` for the rationale). |
| |
| |
| .. method:: socket.recvfrom(bufsize[, flags]) |
| |
| Receive data from the socket. The return value is a pair ``(bytes, address)`` |
| where *bytes* is a bytes object representing the data received and *address* is the |
| address of the socket sending the data. See the Unix manual page |
| :manpage:`recv(2)` for the meaning of the optional argument *flags*; it defaults |
| to zero. (The format of *address* depends on the address family --- see above.) |
| |
| .. versionchanged:: 3.5 |
| If the system call is interrupted and the signal handler does not raise |
| an exception, the method now retries the system call instead of raising |
| an :exc:`InterruptedError` exception (see :pep:`475` for the rationale). |
| |
| .. versionchanged:: 3.7 |
| For multicast IPv6 address, first item of *address* does not contain |
| ``%scope_id`` part anymore. In order to get full IPv6 address use |
| :func:`getnameinfo`. |
| |
| .. method:: socket.recvmsg(bufsize[, ancbufsize[, flags]]) |
| |
| Receive normal data (up to *bufsize* bytes) and ancillary data from |
| the socket. The *ancbufsize* argument sets the size in bytes of |
| the internal buffer used to receive the ancillary data; it defaults |
| to 0, meaning that no ancillary data will be received. Appropriate |
| buffer sizes for ancillary data can be calculated using |
| :func:`CMSG_SPACE` or :func:`CMSG_LEN`, and items which do not fit |
| into the buffer might be truncated or discarded. The *flags* |
| argument defaults to 0 and has the same meaning as for |
| :meth:`recv`. |
| |
| The return value is a 4-tuple: ``(data, ancdata, msg_flags, |
| address)``. The *data* item is a :class:`bytes` object holding the |
| non-ancillary data received. The *ancdata* item is a list of zero |
| or more tuples ``(cmsg_level, cmsg_type, cmsg_data)`` representing |
| the ancillary data (control messages) received: *cmsg_level* and |
| *cmsg_type* are integers specifying the protocol level and |
| protocol-specific type respectively, and *cmsg_data* is a |
| :class:`bytes` object holding the associated data. The *msg_flags* |
| item is the bitwise OR of various flags indicating conditions on |
| the received message; see your system documentation for details. |
| If the receiving socket is unconnected, *address* is the address of |
| the sending socket, if available; otherwise, its value is |
| unspecified. |
| |
| On some systems, :meth:`sendmsg` and :meth:`recvmsg` can be used to |
| pass file descriptors between processes over an :const:`AF_UNIX` |
| socket. When this facility is used (it is often restricted to |
| :const:`SOCK_STREAM` sockets), :meth:`recvmsg` will return, in its |
| ancillary data, items of the form ``(socket.SOL_SOCKET, |
| socket.SCM_RIGHTS, fds)``, where *fds* is a :class:`bytes` object |
| representing the new file descriptors as a binary array of the |
| native C :c:type:`int` type. If :meth:`recvmsg` raises an |
| exception after the system call returns, it will first attempt to |
| close any file descriptors received via this mechanism. |
| |
| Some systems do not indicate the truncated length of ancillary data |
| items which have been only partially received. If an item appears |
| to extend beyond the end of the buffer, :meth:`recvmsg` will issue |
| a :exc:`RuntimeWarning`, and will return the part of it which is |
| inside the buffer provided it has not been truncated before the |
| start of its associated data. |
| |
| On systems which support the :const:`SCM_RIGHTS` mechanism, the |
| following function will receive up to *maxfds* file descriptors, |
| returning the message data and a list containing the descriptors |
| (while ignoring unexpected conditions such as unrelated control |
| messages being received). See also :meth:`sendmsg`. :: |
| |
| import socket, array |
| |
| def recv_fds(sock, msglen, maxfds): |
| fds = array.array("i") # Array of ints |
| msg, ancdata, flags, addr = sock.recvmsg(msglen, socket.CMSG_LEN(maxfds * fds.itemsize)) |
| for cmsg_level, cmsg_type, cmsg_data in ancdata: |
| if cmsg_level == socket.SOL_SOCKET and cmsg_type == socket.SCM_RIGHTS: |
| # Append data, ignoring any truncated integers at the end. |
| fds.frombytes(cmsg_data[:len(cmsg_data) - (len(cmsg_data) % fds.itemsize)]) |
| return msg, list(fds) |
| |
| .. availability:: most Unix platforms, possibly others. |
| |
| .. versionadded:: 3.3 |
| |
| .. versionchanged:: 3.5 |
| If the system call is interrupted and the signal handler does not raise |
| an exception, the method now retries the system call instead of raising |
| an :exc:`InterruptedError` exception (see :pep:`475` for the rationale). |
| |
| |
| .. method:: socket.recvmsg_into(buffers[, ancbufsize[, flags]]) |
| |
| Receive normal data and ancillary data from the socket, behaving as |
| :meth:`recvmsg` would, but scatter the non-ancillary data into a |
| series of buffers instead of returning a new bytes object. The |
| *buffers* argument must be an iterable of objects that export |
| writable buffers (e.g. :class:`bytearray` objects); these will be |
| filled with successive chunks of the non-ancillary data until it |
| has all been written or there are no more buffers. The operating |
| system may set a limit (:func:`~os.sysconf` value ``SC_IOV_MAX``) |
| on the number of buffers that can be used. The *ancbufsize* and |
| *flags* arguments have the same meaning as for :meth:`recvmsg`. |
| |
| The return value is a 4-tuple: ``(nbytes, ancdata, msg_flags, |
| address)``, where *nbytes* is the total number of bytes of |
| non-ancillary data written into the buffers, and *ancdata*, |
| *msg_flags* and *address* are the same as for :meth:`recvmsg`. |
| |
| Example:: |
| |
| >>> import socket |
| >>> s1, s2 = socket.socketpair() |
| >>> b1 = bytearray(b'----') |
| >>> b2 = bytearray(b'0123456789') |
| >>> b3 = bytearray(b'--------------') |
| >>> s1.send(b'Mary had a little lamb') |
| 22 |
| >>> s2.recvmsg_into([b1, memoryview(b2)[2:9], b3]) |
| (22, [], 0, None) |
| >>> [b1, b2, b3] |
| [bytearray(b'Mary'), bytearray(b'01 had a 9'), bytearray(b'little lamb---')] |
| |
| .. availability:: most Unix platforms, possibly others. |
| |
| .. versionadded:: 3.3 |
| |
| |
| .. method:: socket.recvfrom_into(buffer[, nbytes[, flags]]) |
| |
| Receive data from the socket, writing it into *buffer* instead of creating a |
| new bytestring. The return value is a pair ``(nbytes, address)`` where *nbytes* is |
| the number of bytes received and *address* is the address of the socket sending |
| the data. See the Unix manual page :manpage:`recv(2)` for the meaning of the |
| optional argument *flags*; it defaults to zero. (The format of *address* |
| depends on the address family --- see above.) |
| |
| |
| .. method:: socket.recv_into(buffer[, nbytes[, flags]]) |
| |
| Receive up to *nbytes* bytes from the socket, storing the data into a buffer |
| rather than creating a new bytestring. If *nbytes* is not specified (or 0), |
| receive up to the size available in the given buffer. Returns the number of |
| bytes received. See the Unix manual page :manpage:`recv(2)` for the meaning |
| of the optional argument *flags*; it defaults to zero. |
| |
| |
| .. method:: socket.send(bytes[, flags]) |
| |
| Send data to the socket. The socket must be connected to a remote socket. The |
| optional *flags* argument has the same meaning as for :meth:`recv` above. |
| Returns the number of bytes sent. Applications are responsible for checking that |
| all data has been sent; if only some of the data was transmitted, the |
| application needs to attempt delivery of the remaining data. For further |
| information on this topic, consult the :ref:`socket-howto`. |
| |
| .. versionchanged:: 3.5 |
| If the system call is interrupted and the signal handler does not raise |
| an exception, the method now retries the system call instead of raising |
| an :exc:`InterruptedError` exception (see :pep:`475` for the rationale). |
| |
| |
| .. method:: socket.sendall(bytes[, flags]) |
| |
| Send data to the socket. The socket must be connected to a remote socket. The |
| optional *flags* argument has the same meaning as for :meth:`recv` above. |
| Unlike :meth:`send`, this method continues to send data from *bytes* until |
| either all data has been sent or an error occurs. ``None`` is returned on |
| success. On error, an exception is raised, and there is no way to determine how |
| much data, if any, was successfully sent. |
| |
| .. versionchanged:: 3.5 |
| The socket timeout is no more reset each time data is sent successfully. |
| The socket timeout is now the maximum total duration to send all data. |
| |
| .. versionchanged:: 3.5 |
| If the system call is interrupted and the signal handler does not raise |
| an exception, the method now retries the system call instead of raising |
| an :exc:`InterruptedError` exception (see :pep:`475` for the rationale). |
| |
| |
| .. method:: socket.sendto(bytes, address) |
| socket.sendto(bytes, flags, address) |
| |
| Send data to the socket. The socket should not be connected to a remote socket, |
| since the destination socket is specified by *address*. The optional *flags* |
| argument has the same meaning as for :meth:`recv` above. Return the number of |
| bytes sent. (The format of *address* depends on the address family --- see |
| above.) |
| |
| .. audit-event:: socket.sendto self,address socket.socket.sendto |
| |
| .. versionchanged:: 3.5 |
| If the system call is interrupted and the signal handler does not raise |
| an exception, the method now retries the system call instead of raising |
| an :exc:`InterruptedError` exception (see :pep:`475` for the rationale). |
| |
| |
| .. method:: socket.sendmsg(buffers[, ancdata[, flags[, address]]]) |
| |
| Send normal and ancillary data to the socket, gathering the |
| non-ancillary data from a series of buffers and concatenating it |
| into a single message. The *buffers* argument specifies the |
| non-ancillary data as an iterable of |
| :term:`bytes-like objects <bytes-like object>` |
| (e.g. :class:`bytes` objects); the operating system may set a limit |
| (:func:`~os.sysconf` value ``SC_IOV_MAX``) on the number of buffers |
| that can be used. The *ancdata* argument specifies the ancillary |
| data (control messages) as an iterable of zero or more tuples |
| ``(cmsg_level, cmsg_type, cmsg_data)``, where *cmsg_level* and |
| *cmsg_type* are integers specifying the protocol level and |
| protocol-specific type respectively, and *cmsg_data* is a |
| bytes-like object holding the associated data. Note that |
| some systems (in particular, systems without :func:`CMSG_SPACE`) |
| might support sending only one control message per call. The |
| *flags* argument defaults to 0 and has the same meaning as for |
| :meth:`send`. If *address* is supplied and not ``None``, it sets a |
| destination address for the message. The return value is the |
| number of bytes of non-ancillary data sent. |
| |
| The following function sends the list of file descriptors *fds* |
| over an :const:`AF_UNIX` socket, on systems which support the |
| :const:`SCM_RIGHTS` mechanism. See also :meth:`recvmsg`. :: |
| |
| import socket, array |
| |
| def send_fds(sock, msg, fds): |
| return sock.sendmsg([msg], [(socket.SOL_SOCKET, socket.SCM_RIGHTS, array.array("i", fds))]) |
| |
| .. availability:: most Unix platforms, possibly others. |
| |
| .. audit-event:: socket.sendmsg self,address socket.socket.sendmsg |
| |
| .. versionadded:: 3.3 |
| |
| .. versionchanged:: 3.5 |
| If the system call is interrupted and the signal handler does not raise |
| an exception, the method now retries the system call instead of raising |
| an :exc:`InterruptedError` exception (see :pep:`475` for the rationale). |
| |
| .. method:: socket.sendmsg_afalg([msg], *, op[, iv[, assoclen[, flags]]]) |
| |
| Specialized version of :meth:`~socket.sendmsg` for :const:`AF_ALG` socket. |
| Set mode, IV, AEAD associated data length and flags for :const:`AF_ALG` socket. |
| |
| .. availability:: Linux >= 2.6.38. |
| |
| .. versionadded:: 3.6 |
| |
| .. method:: socket.send_fds(sock, buffers, fds[, flags[, address]]) |
| |
| Send the list of file descriptors *fds* over an :const:`AF_UNIX` socket. |
| The *fds* parameter is a sequence of file descriptors. |
| Consult :meth:`sendmsg` for the documentation of these parameters. |
| |
| .. availability:: Unix supporting :meth:`~socket.sendmsg` and :const:`SCM_RIGHTS` mechanism. |
| |
| .. versionadded:: 3.9 |
| |
| .. method:: socket.recv_fds(sock, bufsize, maxfds[, flags]) |
| |
| Receive up to *maxfds* file descriptors. Return ``(msg, list(fds), flags, addr)``. Consult |
| :meth:`recvmsg` for the documentation of these parameters. |
| |
| .. availability:: Unix supporting :meth:`~socket.recvmsg` and :const:`SCM_RIGHTS` mechanism. |
| |
| .. versionadded:: 3.9 |
| |
| .. note:: |
| |
| Any truncated integers at the end of the list of file descriptors. |
| |
| .. method:: socket.sendfile(file, offset=0, count=None) |
| |
| Send a file until EOF is reached by using high-performance |
| :mod:`os.sendfile` and return the total number of bytes which were sent. |
| *file* must be a regular file object opened in binary mode. If |
| :mod:`os.sendfile` is not available (e.g. Windows) or *file* is not a |
| regular file :meth:`send` will be used instead. *offset* tells from where to |
| start reading the file. If specified, *count* is the total number of bytes |
| to transmit as opposed to sending the file until EOF is reached. File |
| position is updated on return or also in case of error in which case |
| :meth:`file.tell() <io.IOBase.tell>` can be used to figure out the number of |
| bytes which were sent. The socket must be of :const:`SOCK_STREAM` type. |
| Non-blocking sockets are not supported. |
| |
| .. versionadded:: 3.5 |
| |
| .. method:: socket.set_inheritable(inheritable) |
| |
| Set the :ref:`inheritable flag <fd_inheritance>` of the socket's file |
| descriptor or socket's handle. |
| |
| .. versionadded:: 3.4 |
| |
| |
| .. method:: socket.setblocking(flag) |
| |
| Set blocking or non-blocking mode of the socket: if *flag* is false, the |
| socket is set to non-blocking, else to blocking mode. |
| |
| This method is a shorthand for certain :meth:`~socket.settimeout` calls: |
| |
| * ``sock.setblocking(True)`` is equivalent to ``sock.settimeout(None)`` |
| |
| * ``sock.setblocking(False)`` is equivalent to ``sock.settimeout(0.0)`` |
| |
| .. versionchanged:: 3.7 |
| The method no longer applies :const:`SOCK_NONBLOCK` flag on |
| :attr:`socket.type`. |
| |
| |
| .. method:: socket.settimeout(value) |
| |
| Set a timeout on blocking socket operations. The *value* argument can be a |
| nonnegative floating point number expressing seconds, or ``None``. |
| If a non-zero value is given, subsequent socket operations will raise a |
| :exc:`timeout` exception if the timeout period *value* has elapsed before |
| the operation has completed. If zero is given, the socket is put in |
| non-blocking mode. If ``None`` is given, the socket is put in blocking mode. |
| |
| For further information, please consult the :ref:`notes on socket timeouts <socket-timeouts>`. |
| |
| .. versionchanged:: 3.7 |
| The method no longer toggles :const:`SOCK_NONBLOCK` flag on |
| :attr:`socket.type`. |
| |
| |
| .. method:: socket.setsockopt(level, optname, value: int) |
| .. method:: socket.setsockopt(level, optname, value: buffer) |
| :noindex: |
| .. method:: socket.setsockopt(level, optname, None, optlen: int) |
| :noindex: |
| |
| .. index:: module: struct |
| |
| Set the value of the given socket option (see the Unix manual page |
| :manpage:`setsockopt(2)`). The needed symbolic constants are defined in the |
| :mod:`socket` module (:const:`SO_\*` etc.). The value can be an integer, |
| ``None`` or a :term:`bytes-like object` representing a buffer. In the later |
| case it is up to the caller to ensure that the bytestring contains the |
| proper bits (see the optional built-in module :mod:`struct` for a way to |
| encode C structures as bytestrings). When *value* is set to ``None``, |
| *optlen* argument is required. It's equivalent to call :c:func:`setsockopt` C |
| function with ``optval=NULL`` and ``optlen=optlen``. |
| |
| |
| .. versionchanged:: 3.5 |
| Writable :term:`bytes-like object` is now accepted. |
| |
| .. versionchanged:: 3.6 |
| setsockopt(level, optname, None, optlen: int) form added. |
| |
| |
| .. method:: socket.shutdown(how) |
| |
| Shut down one or both halves of the connection. If *how* is :const:`SHUT_RD`, |
| further receives are disallowed. If *how* is :const:`SHUT_WR`, further sends |
| are disallowed. If *how* is :const:`SHUT_RDWR`, further sends and receives are |
| disallowed. |
| |
| |
| .. method:: socket.share(process_id) |
| |
| Duplicate a socket and prepare it for sharing with a target process. The |
| target process must be provided with *process_id*. The resulting bytes object |
| can then be passed to the target process using some form of interprocess |
| communication and the socket can be recreated there using :func:`fromshare`. |
| Once this method has been called, it is safe to close the socket since |
| the operating system has already duplicated it for the target process. |
| |
| .. availability:: Windows. |
| |
| .. versionadded:: 3.3 |
| |
| |
| Note that there are no methods :meth:`read` or :meth:`write`; use |
| :meth:`~socket.recv` and :meth:`~socket.send` without *flags* argument instead. |
| |
| Socket objects also have these (read-only) attributes that correspond to the |
| values given to the :class:`~socket.socket` constructor. |
| |
| |
| .. attribute:: socket.family |
| |
| The socket family. |
| |
| |
| .. attribute:: socket.type |
| |
| The socket type. |
| |
| |
| .. attribute:: socket.proto |
| |
| The socket protocol. |
| |
| |
| |
| .. _socket-timeouts: |
| |
| Notes on socket timeouts |
| ------------------------ |
| |
| A socket object can be in one of three modes: blocking, non-blocking, or |
| timeout. Sockets are by default always created in blocking mode, but this |
| can be changed by calling :func:`setdefaulttimeout`. |
| |
| * In *blocking mode*, operations block until complete or the system returns |
| an error (such as connection timed out). |
| |
| * In *non-blocking mode*, operations fail (with an error that is unfortunately |
| system-dependent) if they cannot be completed immediately: functions from the |
| :mod:`select` can be used to know when and whether a socket is available for |
| reading or writing. |
| |
| * In *timeout mode*, operations fail if they cannot be completed within the |
| timeout specified for the socket (they raise a :exc:`timeout` exception) |
| or if the system returns an error. |
| |
| .. note:: |
| At the operating system level, sockets in *timeout mode* are internally set |
| in non-blocking mode. Also, the blocking and timeout modes are shared between |
| file descriptors and socket objects that refer to the same network endpoint. |
| This implementation detail can have visible consequences if e.g. you decide |
| to use the :meth:`~socket.fileno()` of a socket. |
| |
| Timeouts and the ``connect`` method |
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
| |
| The :meth:`~socket.connect` operation is also subject to the timeout |
| setting, and in general it is recommended to call :meth:`~socket.settimeout` |
| before calling :meth:`~socket.connect` or pass a timeout parameter to |
| :meth:`create_connection`. However, the system network stack may also |
| return a connection timeout error of its own regardless of any Python socket |
| timeout setting. |
| |
| Timeouts and the ``accept`` method |
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
| |
| If :func:`getdefaulttimeout` is not :const:`None`, sockets returned by |
| the :meth:`~socket.accept` method inherit that timeout. Otherwise, the |
| behaviour depends on settings of the listening socket: |
| |
| * if the listening socket is in *blocking mode* or in *timeout mode*, |
| the socket returned by :meth:`~socket.accept` is in *blocking mode*; |
| |
| * if the listening socket is in *non-blocking mode*, whether the socket |
| returned by :meth:`~socket.accept` is in blocking or non-blocking mode |
| is operating system-dependent. If you want to ensure cross-platform |
| behaviour, it is recommended you manually override this setting. |
| |
| |
| .. _socket-example: |
| |
| Example |
| ------- |
| |
| Here are four minimal example programs using the TCP/IP protocol: a server that |
| echoes all data that it receives back (servicing only one client), and a client |
| using it. Note that a server must perform the sequence :func:`.socket`, |
| :meth:`~socket.bind`, :meth:`~socket.listen`, :meth:`~socket.accept` (possibly |
| repeating the :meth:`~socket.accept` to service more than one client), while a |
| client only needs the sequence :func:`.socket`, :meth:`~socket.connect`. Also |
| note that the server does not :meth:`~socket.sendall`/:meth:`~socket.recv` on |
| the socket it is listening on but on the new socket returned by |
| :meth:`~socket.accept`. |
| |
| The first two examples support IPv4 only. :: |
| |
| # Echo server program |
| import socket |
| |
| HOST = '' # Symbolic name meaning all available interfaces |
| PORT = 50007 # Arbitrary non-privileged port |
| with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s: |
| s.bind((HOST, PORT)) |
| s.listen(1) |
| conn, addr = s.accept() |
| with conn: |
| print('Connected by', addr) |
| while True: |
| data = conn.recv(1024) |
| if not data: break |
| conn.sendall(data) |
| |
| :: |
| |
| # Echo client program |
| import socket |
| |
| HOST = 'daring.cwi.nl' # The remote host |
| PORT = 50007 # The same port as used by the server |
| with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s: |
| s.connect((HOST, PORT)) |
| s.sendall(b'Hello, world') |
| data = s.recv(1024) |
| print('Received', repr(data)) |
| |
| The next two examples are identical to the above two, but support both IPv4 and |
| IPv6. The server side will listen to the first address family available (it |
| should listen to both instead). On most of IPv6-ready systems, IPv6 will take |
| precedence and the server may not accept IPv4 traffic. The client side will try |
| to connect to the all addresses returned as a result of the name resolution, and |
| sends traffic to the first one connected successfully. :: |
| |
| # Echo server program |
| import socket |
| import sys |
| |
| HOST = None # Symbolic name meaning all available interfaces |
| PORT = 50007 # Arbitrary non-privileged port |
| s = None |
| for res in socket.getaddrinfo(HOST, PORT, socket.AF_UNSPEC, |
| socket.SOCK_STREAM, 0, socket.AI_PASSIVE): |
| af, socktype, proto, canonname, sa = res |
| try: |
| s = socket.socket(af, socktype, proto) |
| except OSError as msg: |
| s = None |
| continue |
| try: |
| s.bind(sa) |
| s.listen(1) |
| except OSError as msg: |
| s.close() |
| s = None |
| continue |
| break |
| if s is None: |
| print('could not open socket') |
| sys.exit(1) |
| conn, addr = s.accept() |
| with conn: |
| print('Connected by', addr) |
| while True: |
| data = conn.recv(1024) |
| if not data: break |
| conn.send(data) |
| |
| :: |
| |
| # Echo client program |
| import socket |
| import sys |
| |
| HOST = 'daring.cwi.nl' # The remote host |
| PORT = 50007 # The same port as used by the server |
| s = None |
| for res in socket.getaddrinfo(HOST, PORT, socket.AF_UNSPEC, socket.SOCK_STREAM): |
| af, socktype, proto, canonname, sa = res |
| try: |
| s = socket.socket(af, socktype, proto) |
| except OSError as msg: |
| s = None |
| continue |
| try: |
| s.connect(sa) |
| except OSError as msg: |
| s.close() |
| s = None |
| continue |
| break |
| if s is None: |
| print('could not open socket') |
| sys.exit(1) |
| with s: |
| s.sendall(b'Hello, world') |
| data = s.recv(1024) |
| print('Received', repr(data)) |
| |
| The next example shows how to write a very simple network sniffer with raw |
| sockets on Windows. The example requires administrator privileges to modify |
| the interface:: |
| |
| import socket |
| |
| # the public network interface |
| HOST = socket.gethostbyname(socket.gethostname()) |
| |
| # create a raw socket and bind it to the public interface |
| s = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_IP) |
| s.bind((HOST, 0)) |
| |
| # Include IP headers |
| s.setsockopt(socket.IPPROTO_IP, socket.IP_HDRINCL, 1) |
| |
| # receive all packages |
| s.ioctl(socket.SIO_RCVALL, socket.RCVALL_ON) |
| |
| # receive a package |
| print(s.recvfrom(65565)) |
| |
| # disabled promiscuous mode |
| s.ioctl(socket.SIO_RCVALL, socket.RCVALL_OFF) |
| |
| The next example shows how to use the socket interface to communicate to a CAN |
| network using the raw socket protocol. To use CAN with the broadcast |
| manager protocol instead, open a socket with:: |
| |
| socket.socket(socket.AF_CAN, socket.SOCK_DGRAM, socket.CAN_BCM) |
| |
| After binding (:const:`CAN_RAW`) or connecting (:const:`CAN_BCM`) the socket, you |
| can use the :meth:`socket.send`, and the :meth:`socket.recv` operations (and |
| their counterparts) on the socket object as usual. |
| |
| This last example might require special privileges:: |
| |
| import socket |
| import struct |
| |
| |
| # CAN frame packing/unpacking (see 'struct can_frame' in <linux/can.h>) |
| |
| can_frame_fmt = "=IB3x8s" |
| can_frame_size = struct.calcsize(can_frame_fmt) |
| |
| def build_can_frame(can_id, data): |
| can_dlc = len(data) |
| data = data.ljust(8, b'\x00') |
| return struct.pack(can_frame_fmt, can_id, can_dlc, data) |
| |
| def dissect_can_frame(frame): |
| can_id, can_dlc, data = struct.unpack(can_frame_fmt, frame) |
| return (can_id, can_dlc, data[:can_dlc]) |
| |
| |
| # create a raw socket and bind it to the 'vcan0' interface |
| s = socket.socket(socket.AF_CAN, socket.SOCK_RAW, socket.CAN_RAW) |
| s.bind(('vcan0',)) |
| |
| while True: |
| cf, addr = s.recvfrom(can_frame_size) |
| |
| print('Received: can_id=%x, can_dlc=%x, data=%s' % dissect_can_frame(cf)) |
| |
| try: |
| s.send(cf) |
| except OSError: |
| print('Error sending CAN frame') |
| |
| try: |
| s.send(build_can_frame(0x01, b'\x01\x02\x03')) |
| except OSError: |
| print('Error sending CAN frame') |
| |
| Running an example several times with too small delay between executions, could |
| lead to this error:: |
| |
| OSError: [Errno 98] Address already in use |
| |
| This is because the previous execution has left the socket in a ``TIME_WAIT`` |
| state, and can't be immediately reused. |
| |
| There is a :mod:`socket` flag to set, in order to prevent this, |
| :data:`socket.SO_REUSEADDR`:: |
| |
| s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) |
| s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) |
| s.bind((HOST, PORT)) |
| |
| the :data:`SO_REUSEADDR` flag tells the kernel to reuse a local socket in |
| ``TIME_WAIT`` state, without waiting for its natural timeout to expire. |
| |
| |
| .. seealso:: |
| |
| For an introduction to socket programming (in C), see the following papers: |
| |
| - *An Introductory 4.3BSD Interprocess Communication Tutorial*, by Stuart Sechrest |
| |
| - *An Advanced 4.3BSD Interprocess Communication Tutorial*, by Samuel J. Leffler et |
| al, |
| |
| both in the UNIX Programmer's Manual, Supplementary Documents 1 (sections |
| PS1:7 and PS1:8). The platform-specific reference material for the various |
| socket-related system calls are also a valuable source of information on the |
| details of socket semantics. For Unix, refer to the manual pages; for Windows, |
| see the WinSock (or Winsock 2) specification. For IPv6-ready APIs, readers may |
| want to refer to :rfc:`3493` titled Basic Socket Interface Extensions for IPv6. |