Alexandre Vassalotti | ce26195 | 2008-05-12 02:31:37 +0000 | [diff] [blame] | 1 | :mod:`socketserver` --- A framework for network servers |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 2 | ======================================================= |
| 3 | |
Alexandre Vassalotti | ce26195 | 2008-05-12 02:31:37 +0000 | [diff] [blame] | 4 | .. module:: socketserver |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 5 | :synopsis: A framework for network servers. |
| 6 | |
Raymond Hettinger | 469271d | 2011-01-27 20:38:46 +0000 | [diff] [blame] | 7 | **Source code:** :source:`Lib/socketserver.py` |
| 8 | |
| 9 | -------------- |
| 10 | |
Alexandre Vassalotti | ce26195 | 2008-05-12 02:31:37 +0000 | [diff] [blame] | 11 | The :mod:`socketserver` module simplifies the task of writing network servers. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 12 | |
| 13 | There are four basic server classes: :class:`TCPServer` uses the Internet TCP |
| 14 | protocol, which provides for continuous streams of data between the client and |
| 15 | server. :class:`UDPServer` uses datagrams, which are discrete packets of |
| 16 | information that may arrive out of order or be lost while in transit. The more |
| 17 | infrequently used :class:`UnixStreamServer` and :class:`UnixDatagramServer` |
| 18 | classes are similar, but use Unix domain sockets; they're not available on |
| 19 | non-Unix platforms. For more details on network programming, consult a book |
| 20 | such as |
| 21 | W. Richard Steven's UNIX Network Programming or Ralph Davis's Win32 Network |
| 22 | Programming. |
| 23 | |
| 24 | These four classes process requests :dfn:`synchronously`; each request must be |
| 25 | completed before the next request can be started. This isn't suitable if each |
| 26 | request takes a long time to complete, because it requires a lot of computation, |
| 27 | or because it returns a lot of data which the client is slow to process. The |
| 28 | solution is to create a separate process or thread to handle each request; the |
| 29 | :class:`ForkingMixIn` and :class:`ThreadingMixIn` mix-in classes can be used to |
| 30 | support asynchronous behaviour. |
| 31 | |
| 32 | Creating a server requires several steps. First, you must create a request |
| 33 | handler class by subclassing the :class:`BaseRequestHandler` class and |
| 34 | overriding its :meth:`handle` method; this method will process incoming |
| 35 | requests. Second, you must instantiate one of the server classes, passing it |
| 36 | the server's address and the request handler class. Finally, call the |
| 37 | :meth:`handle_request` or :meth:`serve_forever` method of the server object to |
| 38 | process one or many requests. |
| 39 | |
| 40 | When inheriting from :class:`ThreadingMixIn` for threaded connection behavior, |
| 41 | you should explicitly declare how you want your threads to behave on an abrupt |
Florent Xicluna | 599d76b | 2011-11-11 19:56:26 +0100 | [diff] [blame] | 42 | shutdown. The :class:`ThreadingMixIn` class defines an attribute |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 43 | *daemon_threads*, which indicates whether or not the server should wait for |
Florent Xicluna | 599d76b | 2011-11-11 19:56:26 +0100 | [diff] [blame] | 44 | thread termination. You should set the flag explicitly if you would like |
| 45 | threads to behave autonomously; the default is :const:`False`, meaning that |
| 46 | Python will not exit until all threads created by :class:`ThreadingMixIn` have |
| 47 | exited. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 48 | |
| 49 | Server classes have the same external methods and attributes, no matter what |
Georg Brandl | fceab5a | 2008-01-19 20:08:23 +0000 | [diff] [blame] | 50 | network protocol they use. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 51 | |
| 52 | |
| 53 | Server Creation Notes |
| 54 | --------------------- |
| 55 | |
| 56 | There are five classes in an inheritance diagram, four of which represent |
| 57 | synchronous servers of four types:: |
| 58 | |
| 59 | +------------+ |
| 60 | | BaseServer | |
| 61 | +------------+ |
| 62 | | |
| 63 | v |
| 64 | +-----------+ +------------------+ |
| 65 | | TCPServer |------->| UnixStreamServer | |
| 66 | +-----------+ +------------------+ |
| 67 | | |
| 68 | v |
| 69 | +-----------+ +--------------------+ |
| 70 | | UDPServer |------->| UnixDatagramServer | |
| 71 | +-----------+ +--------------------+ |
| 72 | |
| 73 | Note that :class:`UnixDatagramServer` derives from :class:`UDPServer`, not from |
| 74 | :class:`UnixStreamServer` --- the only difference between an IP and a Unix |
| 75 | stream server is the address family, which is simply repeated in both Unix |
| 76 | server classes. |
| 77 | |
| 78 | Forking and threading versions of each type of server can be created using the |
| 79 | :class:`ForkingMixIn` and :class:`ThreadingMixIn` mix-in classes. For instance, |
| 80 | a threading UDP server class is created as follows:: |
| 81 | |
| 82 | class ThreadingUDPServer(ThreadingMixIn, UDPServer): pass |
| 83 | |
| 84 | The mix-in class must come first, since it overrides a method defined in |
Senthil Kumaran | a6bac95 | 2011-07-04 11:28:30 -0700 | [diff] [blame] | 85 | :class:`UDPServer`. Setting the various attributes also change the |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 86 | behavior of the underlying server mechanism. |
| 87 | |
| 88 | To implement a service, you must derive a class from :class:`BaseRequestHandler` |
| 89 | and redefine its :meth:`handle` method. You can then run various versions of |
| 90 | the service by combining one of the server classes with your request handler |
| 91 | class. The request handler class must be different for datagram or stream |
| 92 | services. This can be hidden by using the handler subclasses |
| 93 | :class:`StreamRequestHandler` or :class:`DatagramRequestHandler`. |
| 94 | |
| 95 | Of course, you still have to use your head! For instance, it makes no sense to |
| 96 | use a forking server if the service contains state in memory that can be |
| 97 | modified by different requests, since the modifications in the child process |
| 98 | would never reach the initial state kept in the parent process and passed to |
| 99 | each child. In this case, you can use a threading server, but you will probably |
| 100 | have to use locks to protect the integrity of the shared data. |
| 101 | |
| 102 | On the other hand, if you are building an HTTP server where all data is stored |
| 103 | externally (for instance, in the file system), a synchronous class will |
| 104 | essentially render the service "deaf" while one request is being handled -- |
| 105 | which may be for a very long time if a client is slow to receive all the data it |
| 106 | has requested. Here a threading or forking server is appropriate. |
| 107 | |
| 108 | In some cases, it may be appropriate to process part of a request synchronously, |
| 109 | but to finish processing in a forked child depending on the request data. This |
| 110 | can be implemented by using a synchronous server and doing an explicit fork in |
| 111 | the request handler class :meth:`handle` method. |
| 112 | |
| 113 | Another approach to handling multiple simultaneous requests in an environment |
Serhiy Storchaka | bfdcd43 | 2013-10-13 23:09:14 +0300 | [diff] [blame] | 114 | that supports neither threads nor :func:`~os.fork` (or where these are too |
| 115 | expensive or inappropriate for the service) is to maintain an explicit table of |
| 116 | partially finished requests and to use :func:`~select.select` to decide which |
| 117 | request to work on next (or whether to handle a new incoming request). This is |
| 118 | particularly important for stream services where each client can potentially be |
| 119 | connected for a long time (if threads or subprocesses cannot be used). See |
| 120 | :mod:`asyncore` for another way to manage this. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 121 | |
Christian Heimes | 5b5e81c | 2007-12-31 16:14:33 +0000 | [diff] [blame] | 122 | .. XXX should data and methods be intermingled, or separate? |
| 123 | how should the distinction between class and instance variables be drawn? |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 124 | |
| 125 | |
| 126 | Server Objects |
| 127 | -------------- |
| 128 | |
Benjamin Peterson | d23f822 | 2009-04-05 19:13:16 +0000 | [diff] [blame] | 129 | .. class:: BaseServer |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 130 | |
Benjamin Peterson | d23f822 | 2009-04-05 19:13:16 +0000 | [diff] [blame] | 131 | This is the superclass of all Server objects in the module. It defines the |
| 132 | interface, given below, but does not implement most of the methods, which is |
| 133 | done in subclasses. |
| 134 | |
| 135 | |
| 136 | .. method:: BaseServer.fileno() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 137 | |
| 138 | Return an integer file descriptor for the socket on which the server is |
| 139 | listening. This function is most commonly passed to :func:`select.select`, to |
| 140 | allow monitoring multiple servers in the same process. |
| 141 | |
| 142 | |
Benjamin Peterson | d23f822 | 2009-04-05 19:13:16 +0000 | [diff] [blame] | 143 | .. method:: BaseServer.handle_request() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 144 | |
Christian Heimes | dd15f6c | 2008-03-16 00:07:10 +0000 | [diff] [blame] | 145 | Process a single request. This function calls the following methods in |
| 146 | order: :meth:`get_request`, :meth:`verify_request`, and |
| 147 | :meth:`process_request`. If the user-provided :meth:`handle` method of the |
| 148 | handler class raises an exception, the server's :meth:`handle_error` method |
| 149 | will be called. If no request is received within :attr:`self.timeout` |
| 150 | seconds, :meth:`handle_timeout` will be called and :meth:`handle_request` |
| 151 | will return. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 152 | |
| 153 | |
Benjamin Peterson | d23f822 | 2009-04-05 19:13:16 +0000 | [diff] [blame] | 154 | .. method:: BaseServer.serve_forever(poll_interval=0.5) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 155 | |
R David Murray | 258fabe | 2012-10-01 21:43:46 -0400 | [diff] [blame] | 156 | Handle requests until an explicit :meth:`shutdown` request. Poll for |
| 157 | shutdown every *poll_interval* seconds. Ignores :attr:`self.timeout`. It |
| 158 | also calls :meth:`service_actions`, which may be used by a subclass or mixin |
| 159 | to provide actions specific to a given service. For example, the |
| 160 | :class:`ForkingMixIn` class uses :meth:`service_actions` to clean up zombie |
| 161 | child processes. |
Christian Heimes | dd15f6c | 2008-03-16 00:07:10 +0000 | [diff] [blame] | 162 | |
Senthil Kumaran | 5e826e8 | 2011-05-26 00:22:59 +0800 | [diff] [blame] | 163 | .. versionchanged:: 3.3 |
R David Murray | 258fabe | 2012-10-01 21:43:46 -0400 | [diff] [blame] | 164 | Added ``service_actions`` call to the ``serve_forever`` method. |
Senthil Kumaran | 5e826e8 | 2011-05-26 00:22:59 +0800 | [diff] [blame] | 165 | |
| 166 | |
| 167 | .. method:: BaseServer.service_actions() |
| 168 | |
Ezio Melotti | a3b255f | 2013-04-12 19:19:21 +0300 | [diff] [blame] | 169 | This is called in the :meth:`serve_forever` loop. This method can be |
R David Murray | 258fabe | 2012-10-01 21:43:46 -0400 | [diff] [blame] | 170 | overridden by subclasses or mixin classes to perform actions specific to |
| 171 | a given service, such as cleanup actions. |
Senthil Kumaran | 5e826e8 | 2011-05-26 00:22:59 +0800 | [diff] [blame] | 172 | |
| 173 | .. versionadded:: 3.3 |
Christian Heimes | dd15f6c | 2008-03-16 00:07:10 +0000 | [diff] [blame] | 174 | |
Benjamin Peterson | d23f822 | 2009-04-05 19:13:16 +0000 | [diff] [blame] | 175 | .. method:: BaseServer.shutdown() |
Christian Heimes | dd15f6c | 2008-03-16 00:07:10 +0000 | [diff] [blame] | 176 | |
Sandro Tosi | 753b79c | 2012-01-03 22:35:54 +0100 | [diff] [blame] | 177 | Tell the :meth:`serve_forever` loop to stop and wait until it does. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 178 | |
| 179 | |
Benjamin Peterson | d23f822 | 2009-04-05 19:13:16 +0000 | [diff] [blame] | 180 | .. attribute:: BaseServer.address_family |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 181 | |
| 182 | The family of protocols to which the server's socket belongs. |
Alexandre Vassalotti | 5f8ced2 | 2008-05-16 00:03:33 +0000 | [diff] [blame] | 183 | Common examples are :const:`socket.AF_INET` and :const:`socket.AF_UNIX`. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 184 | |
| 185 | |
Benjamin Peterson | d23f822 | 2009-04-05 19:13:16 +0000 | [diff] [blame] | 186 | .. attribute:: BaseServer.RequestHandlerClass |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 187 | |
| 188 | The user-provided request handler class; an instance of this class is created |
| 189 | for each request. |
| 190 | |
| 191 | |
Benjamin Peterson | d23f822 | 2009-04-05 19:13:16 +0000 | [diff] [blame] | 192 | .. attribute:: BaseServer.server_address |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 193 | |
| 194 | The address on which the server is listening. The format of addresses varies |
| 195 | depending on the protocol family; see the documentation for the socket module |
| 196 | for details. For Internet protocols, this is a tuple containing a string giving |
| 197 | the address, and an integer port number: ``('127.0.0.1', 80)``, for example. |
| 198 | |
| 199 | |
Benjamin Peterson | d23f822 | 2009-04-05 19:13:16 +0000 | [diff] [blame] | 200 | .. attribute:: BaseServer.socket |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 201 | |
| 202 | The socket object on which the server will listen for incoming requests. |
| 203 | |
Benjamin Peterson | d23f822 | 2009-04-05 19:13:16 +0000 | [diff] [blame] | 204 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 205 | The server classes support the following class variables: |
| 206 | |
Christian Heimes | 5b5e81c | 2007-12-31 16:14:33 +0000 | [diff] [blame] | 207 | .. XXX should class variables be covered before instance variables, or vice versa? |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 208 | |
Benjamin Peterson | d23f822 | 2009-04-05 19:13:16 +0000 | [diff] [blame] | 209 | .. attribute:: BaseServer.allow_reuse_address |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 210 | |
Florent Xicluna | 599d76b | 2011-11-11 19:56:26 +0100 | [diff] [blame] | 211 | Whether the server will allow the reuse of an address. This defaults to |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 212 | :const:`False`, and can be set in subclasses to change the policy. |
| 213 | |
| 214 | |
Benjamin Peterson | d23f822 | 2009-04-05 19:13:16 +0000 | [diff] [blame] | 215 | .. attribute:: BaseServer.request_queue_size |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 216 | |
| 217 | The size of the request queue. If it takes a long time to process a single |
| 218 | request, any requests that arrive while the server is busy are placed into a |
| 219 | queue, up to :attr:`request_queue_size` requests. Once the queue is full, |
| 220 | further requests from clients will get a "Connection denied" error. The default |
| 221 | value is usually 5, but this can be overridden by subclasses. |
| 222 | |
| 223 | |
Benjamin Peterson | d23f822 | 2009-04-05 19:13:16 +0000 | [diff] [blame] | 224 | .. attribute:: BaseServer.socket_type |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 225 | |
| 226 | The type of socket used by the server; :const:`socket.SOCK_STREAM` and |
Alexandre Vassalotti | 5f8ced2 | 2008-05-16 00:03:33 +0000 | [diff] [blame] | 227 | :const:`socket.SOCK_DGRAM` are two common values. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 228 | |
Benjamin Peterson | d23f822 | 2009-04-05 19:13:16 +0000 | [diff] [blame] | 229 | |
| 230 | .. attribute:: BaseServer.timeout |
Georg Brandl | fceab5a | 2008-01-19 20:08:23 +0000 | [diff] [blame] | 231 | |
Christian Heimes | dd15f6c | 2008-03-16 00:07:10 +0000 | [diff] [blame] | 232 | Timeout duration, measured in seconds, or :const:`None` if no timeout is |
| 233 | desired. If :meth:`handle_request` receives no incoming requests within the |
| 234 | timeout period, the :meth:`handle_timeout` method is called. |
Georg Brandl | fceab5a | 2008-01-19 20:08:23 +0000 | [diff] [blame] | 235 | |
Benjamin Peterson | d23f822 | 2009-04-05 19:13:16 +0000 | [diff] [blame] | 236 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 237 | There are various server methods that can be overridden by subclasses of base |
| 238 | server classes like :class:`TCPServer`; these methods aren't useful to external |
| 239 | users of the server object. |
| 240 | |
Christian Heimes | 5b5e81c | 2007-12-31 16:14:33 +0000 | [diff] [blame] | 241 | .. XXX should the default implementations of these be documented, or should |
Alexandre Vassalotti | ce26195 | 2008-05-12 02:31:37 +0000 | [diff] [blame] | 242 | it be assumed that the user will look at socketserver.py? |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 243 | |
Benjamin Peterson | d23f822 | 2009-04-05 19:13:16 +0000 | [diff] [blame] | 244 | .. method:: BaseServer.finish_request() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 245 | |
| 246 | Actually processes the request by instantiating :attr:`RequestHandlerClass` and |
| 247 | calling its :meth:`handle` method. |
| 248 | |
| 249 | |
Benjamin Peterson | d23f822 | 2009-04-05 19:13:16 +0000 | [diff] [blame] | 250 | .. method:: BaseServer.get_request() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 251 | |
| 252 | Must accept a request from the socket, and return a 2-tuple containing the *new* |
| 253 | socket object to be used to communicate with the client, and the client's |
| 254 | address. |
| 255 | |
| 256 | |
Benjamin Peterson | d23f822 | 2009-04-05 19:13:16 +0000 | [diff] [blame] | 257 | .. method:: BaseServer.handle_error(request, client_address) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 258 | |
| 259 | This function is called if the :attr:`RequestHandlerClass`'s :meth:`handle` |
| 260 | method raises an exception. The default action is to print the traceback to |
| 261 | standard output and continue handling further requests. |
| 262 | |
Benjamin Peterson | d23f822 | 2009-04-05 19:13:16 +0000 | [diff] [blame] | 263 | |
| 264 | .. method:: BaseServer.handle_timeout() |
Georg Brandl | fceab5a | 2008-01-19 20:08:23 +0000 | [diff] [blame] | 265 | |
Georg Brandl | b533e26 | 2008-05-25 18:19:30 +0000 | [diff] [blame] | 266 | This function is called when the :attr:`timeout` attribute has been set to a |
| 267 | value other than :const:`None` and the timeout period has passed with no |
Georg Brandl | fceab5a | 2008-01-19 20:08:23 +0000 | [diff] [blame] | 268 | requests being received. The default action for forking servers is |
| 269 | to collect the status of any child processes that have exited, while |
| 270 | in threading servers this method does nothing. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 271 | |
Benjamin Peterson | d23f822 | 2009-04-05 19:13:16 +0000 | [diff] [blame] | 272 | |
| 273 | .. method:: BaseServer.process_request(request, client_address) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 274 | |
| 275 | Calls :meth:`finish_request` to create an instance of the |
| 276 | :attr:`RequestHandlerClass`. If desired, this function can create a new process |
| 277 | or thread to handle the request; the :class:`ForkingMixIn` and |
| 278 | :class:`ThreadingMixIn` classes do this. |
| 279 | |
Benjamin Peterson | d23f822 | 2009-04-05 19:13:16 +0000 | [diff] [blame] | 280 | |
Christian Heimes | 5b5e81c | 2007-12-31 16:14:33 +0000 | [diff] [blame] | 281 | .. Is there any point in documenting the following two functions? |
| 282 | What would the purpose of overriding them be: initializing server |
| 283 | instance variables, adding new network families? |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 284 | |
Benjamin Peterson | d23f822 | 2009-04-05 19:13:16 +0000 | [diff] [blame] | 285 | .. method:: BaseServer.server_activate() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 286 | |
| 287 | Called by the server's constructor to activate the server. The default behavior |
Florent Xicluna | 599d76b | 2011-11-11 19:56:26 +0100 | [diff] [blame] | 288 | just :meth:`listen`\ s to the server's socket. May be overridden. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 289 | |
| 290 | |
Benjamin Peterson | d23f822 | 2009-04-05 19:13:16 +0000 | [diff] [blame] | 291 | .. method:: BaseServer.server_bind() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 292 | |
| 293 | Called by the server's constructor to bind the socket to the desired address. |
| 294 | May be overridden. |
| 295 | |
| 296 | |
Benjamin Peterson | d23f822 | 2009-04-05 19:13:16 +0000 | [diff] [blame] | 297 | .. method:: BaseServer.verify_request(request, client_address) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 298 | |
Florent Xicluna | 599d76b | 2011-11-11 19:56:26 +0100 | [diff] [blame] | 299 | Must return a Boolean value; if the value is :const:`True`, the request will |
| 300 | be processed, and if it's :const:`False`, the request will be denied. This |
| 301 | function can be overridden to implement access controls for a server. The |
| 302 | default implementation always returns :const:`True`. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 303 | |
| 304 | |
| 305 | RequestHandler Objects |
| 306 | ---------------------- |
| 307 | |
| 308 | The request handler class must define a new :meth:`handle` method, and can |
| 309 | override any of the following methods. A new instance is created for each |
| 310 | request. |
| 311 | |
| 312 | |
Benjamin Peterson | d23f822 | 2009-04-05 19:13:16 +0000 | [diff] [blame] | 313 | .. method:: RequestHandler.finish() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 314 | |
Georg Brandl | b533e26 | 2008-05-25 18:19:30 +0000 | [diff] [blame] | 315 | Called after the :meth:`handle` method to perform any clean-up actions |
Kristján Valur Jónsson | 36852b7 | 2012-12-25 22:46:32 +0000 | [diff] [blame] | 316 | required. The default implementation does nothing. If :meth:`setup` |
| 317 | raises an exception, this function will not be called. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 318 | |
| 319 | |
Benjamin Peterson | d23f822 | 2009-04-05 19:13:16 +0000 | [diff] [blame] | 320 | .. method:: RequestHandler.handle() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 321 | |
Georg Brandl | b533e26 | 2008-05-25 18:19:30 +0000 | [diff] [blame] | 322 | This function must do all the work required to service a request. The |
| 323 | default implementation does nothing. Several instance attributes are |
| 324 | available to it; the request is available as :attr:`self.request`; the client |
| 325 | address as :attr:`self.client_address`; and the server instance as |
| 326 | :attr:`self.server`, in case it needs access to per-server information. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 327 | |
Georg Brandl | b533e26 | 2008-05-25 18:19:30 +0000 | [diff] [blame] | 328 | The type of :attr:`self.request` is different for datagram or stream |
| 329 | services. For stream services, :attr:`self.request` is a socket object; for |
| 330 | datagram services, :attr:`self.request` is a pair of string and socket. |
| 331 | However, this can be hidden by using the request handler subclasses |
| 332 | :class:`StreamRequestHandler` or :class:`DatagramRequestHandler`, which |
| 333 | override the :meth:`setup` and :meth:`finish` methods, and provide |
| 334 | :attr:`self.rfile` and :attr:`self.wfile` attributes. :attr:`self.rfile` and |
| 335 | :attr:`self.wfile` can be read or written, respectively, to get the request |
| 336 | data or return data to the client. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 337 | |
| 338 | |
Benjamin Peterson | d23f822 | 2009-04-05 19:13:16 +0000 | [diff] [blame] | 339 | .. method:: RequestHandler.setup() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 340 | |
| 341 | Called before the :meth:`handle` method to perform any initialization actions |
| 342 | required. The default implementation does nothing. |
| 343 | |
Georg Brandl | b533e26 | 2008-05-25 18:19:30 +0000 | [diff] [blame] | 344 | |
| 345 | Examples |
| 346 | -------- |
| 347 | |
| 348 | :class:`socketserver.TCPServer` Example |
| 349 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
| 350 | |
| 351 | This is the server side:: |
| 352 | |
| 353 | import socketserver |
| 354 | |
| 355 | class MyTCPHandler(socketserver.BaseRequestHandler): |
| 356 | """ |
| 357 | The RequestHandler class for our server. |
| 358 | |
| 359 | It is instantiated once per connection to the server, and must |
| 360 | override the handle() method to implement communication to the |
| 361 | client. |
| 362 | """ |
| 363 | |
| 364 | def handle(self): |
| 365 | # self.request is the TCP socket connected to the client |
| 366 | self.data = self.request.recv(1024).strip() |
Florent Xicluna | 023611f | 2011-10-23 22:40:37 +0200 | [diff] [blame] | 367 | print("{} wrote:".format(self.client_address[0])) |
Benjamin Peterson | 06fd5f8 | 2008-11-08 17:24:34 +0000 | [diff] [blame] | 368 | print(self.data) |
Georg Brandl | b533e26 | 2008-05-25 18:19:30 +0000 | [diff] [blame] | 369 | # just send back the same data, but upper-cased |
Senthil Kumaran | 6e13f13 | 2012-02-09 17:54:17 +0800 | [diff] [blame] | 370 | self.request.sendall(self.data.upper()) |
Georg Brandl | b533e26 | 2008-05-25 18:19:30 +0000 | [diff] [blame] | 371 | |
| 372 | if __name__ == "__main__": |
| 373 | HOST, PORT = "localhost", 9999 |
| 374 | |
| 375 | # Create the server, binding to localhost on port 9999 |
| 376 | server = socketserver.TCPServer((HOST, PORT), MyTCPHandler) |
| 377 | |
| 378 | # Activate the server; this will keep running until you |
| 379 | # interrupt the program with Ctrl-C |
| 380 | server.serve_forever() |
| 381 | |
| 382 | An alternative request handler class that makes use of streams (file-like |
| 383 | objects that simplify communication by providing the standard file interface):: |
| 384 | |
| 385 | class MyTCPHandler(socketserver.StreamRequestHandler): |
| 386 | |
| 387 | def handle(self): |
| 388 | # self.rfile is a file-like object created by the handler; |
| 389 | # we can now use e.g. readline() instead of raw recv() calls |
| 390 | self.data = self.rfile.readline().strip() |
Florent Xicluna | 023611f | 2011-10-23 22:40:37 +0200 | [diff] [blame] | 391 | print("{} wrote:".format(self.client_address[0])) |
Benjamin Peterson | 06fd5f8 | 2008-11-08 17:24:34 +0000 | [diff] [blame] | 392 | print(self.data) |
Georg Brandl | b533e26 | 2008-05-25 18:19:30 +0000 | [diff] [blame] | 393 | # Likewise, self.wfile is a file-like object used to write back |
| 394 | # to the client |
| 395 | self.wfile.write(self.data.upper()) |
| 396 | |
| 397 | The difference is that the ``readline()`` call in the second handler will call |
| 398 | ``recv()`` multiple times until it encounters a newline character, while the |
| 399 | single ``recv()`` call in the first handler will just return what has been sent |
Senthil Kumaran | 6e13f13 | 2012-02-09 17:54:17 +0800 | [diff] [blame] | 400 | from the client in one ``sendall()`` call. |
Georg Brandl | b533e26 | 2008-05-25 18:19:30 +0000 | [diff] [blame] | 401 | |
| 402 | |
| 403 | This is the client side:: |
| 404 | |
| 405 | import socket |
| 406 | import sys |
| 407 | |
| 408 | HOST, PORT = "localhost", 9999 |
| 409 | data = " ".join(sys.argv[1:]) |
| 410 | |
| 411 | # Create a socket (SOCK_STREAM means a TCP socket) |
| 412 | sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) |
| 413 | |
Florent Xicluna | 023611f | 2011-10-23 22:40:37 +0200 | [diff] [blame] | 414 | try: |
| 415 | # Connect to server and send data |
| 416 | sock.connect((HOST, PORT)) |
Senthil Kumaran | 6e13f13 | 2012-02-09 17:54:17 +0800 | [diff] [blame] | 417 | sock.sendall(bytes(data + "\n", "utf-8")) |
Georg Brandl | b533e26 | 2008-05-25 18:19:30 +0000 | [diff] [blame] | 418 | |
Florent Xicluna | 023611f | 2011-10-23 22:40:37 +0200 | [diff] [blame] | 419 | # Receive data from the server and shut down |
| 420 | received = str(sock.recv(1024), "utf-8") |
| 421 | finally: |
| 422 | sock.close() |
Georg Brandl | b533e26 | 2008-05-25 18:19:30 +0000 | [diff] [blame] | 423 | |
Florent Xicluna | 023611f | 2011-10-23 22:40:37 +0200 | [diff] [blame] | 424 | print("Sent: {}".format(data)) |
| 425 | print("Received: {}".format(received)) |
Georg Brandl | b533e26 | 2008-05-25 18:19:30 +0000 | [diff] [blame] | 426 | |
| 427 | |
| 428 | The output of the example should look something like this: |
| 429 | |
| 430 | Server:: |
| 431 | |
| 432 | $ python TCPServer.py |
| 433 | 127.0.0.1 wrote: |
Benjamin Peterson | 06fd5f8 | 2008-11-08 17:24:34 +0000 | [diff] [blame] | 434 | b'hello world with TCP' |
Georg Brandl | b533e26 | 2008-05-25 18:19:30 +0000 | [diff] [blame] | 435 | 127.0.0.1 wrote: |
Benjamin Peterson | 06fd5f8 | 2008-11-08 17:24:34 +0000 | [diff] [blame] | 436 | b'python is nice' |
Georg Brandl | b533e26 | 2008-05-25 18:19:30 +0000 | [diff] [blame] | 437 | |
| 438 | Client:: |
| 439 | |
| 440 | $ python TCPClient.py hello world with TCP |
| 441 | Sent: hello world with TCP |
Florent Xicluna | 023611f | 2011-10-23 22:40:37 +0200 | [diff] [blame] | 442 | Received: HELLO WORLD WITH TCP |
Georg Brandl | b533e26 | 2008-05-25 18:19:30 +0000 | [diff] [blame] | 443 | $ python TCPClient.py python is nice |
| 444 | Sent: python is nice |
Florent Xicluna | 023611f | 2011-10-23 22:40:37 +0200 | [diff] [blame] | 445 | Received: PYTHON IS NICE |
Georg Brandl | b533e26 | 2008-05-25 18:19:30 +0000 | [diff] [blame] | 446 | |
| 447 | |
| 448 | :class:`socketserver.UDPServer` Example |
| 449 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
| 450 | |
| 451 | This is the server side:: |
| 452 | |
| 453 | import socketserver |
| 454 | |
| 455 | class MyUDPHandler(socketserver.BaseRequestHandler): |
| 456 | """ |
| 457 | This class works similar to the TCP handler class, except that |
| 458 | self.request consists of a pair of data and client socket, and since |
| 459 | there is no connection the client address must be given explicitly |
| 460 | when sending data back via sendto(). |
| 461 | """ |
| 462 | |
| 463 | def handle(self): |
| 464 | data = self.request[0].strip() |
| 465 | socket = self.request[1] |
Florent Xicluna | 023611f | 2011-10-23 22:40:37 +0200 | [diff] [blame] | 466 | print("{} wrote:".format(self.client_address[0])) |
Benjamin Peterson | 06fd5f8 | 2008-11-08 17:24:34 +0000 | [diff] [blame] | 467 | print(data) |
Georg Brandl | b533e26 | 2008-05-25 18:19:30 +0000 | [diff] [blame] | 468 | socket.sendto(data.upper(), self.client_address) |
| 469 | |
| 470 | if __name__ == "__main__": |
Benjamin Peterson | 2021100 | 2009-11-25 18:34:42 +0000 | [diff] [blame] | 471 | HOST, PORT = "localhost", 9999 |
| 472 | server = socketserver.UDPServer((HOST, PORT), MyUDPHandler) |
| 473 | server.serve_forever() |
Georg Brandl | b533e26 | 2008-05-25 18:19:30 +0000 | [diff] [blame] | 474 | |
| 475 | This is the client side:: |
| 476 | |
| 477 | import socket |
| 478 | import sys |
| 479 | |
Benjamin Peterson | 06fd5f8 | 2008-11-08 17:24:34 +0000 | [diff] [blame] | 480 | HOST, PORT = "localhost", 9999 |
Georg Brandl | b533e26 | 2008-05-25 18:19:30 +0000 | [diff] [blame] | 481 | data = " ".join(sys.argv[1:]) |
| 482 | |
| 483 | # SOCK_DGRAM is the socket type to use for UDP sockets |
| 484 | sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) |
| 485 | |
| 486 | # As you can see, there is no connect() call; UDP has no connections. |
| 487 | # Instead, data is directly sent to the recipient via sendto(). |
Florent Xicluna | 023611f | 2011-10-23 22:40:37 +0200 | [diff] [blame] | 488 | sock.sendto(bytes(data + "\n", "utf-8"), (HOST, PORT)) |
| 489 | received = str(sock.recv(1024), "utf-8") |
Georg Brandl | b533e26 | 2008-05-25 18:19:30 +0000 | [diff] [blame] | 490 | |
Florent Xicluna | 023611f | 2011-10-23 22:40:37 +0200 | [diff] [blame] | 491 | print("Sent: {}".format(data)) |
| 492 | print("Received: {}".format(received)) |
Georg Brandl | b533e26 | 2008-05-25 18:19:30 +0000 | [diff] [blame] | 493 | |
| 494 | The output of the example should look exactly like for the TCP server example. |
| 495 | |
| 496 | |
| 497 | Asynchronous Mixins |
| 498 | ~~~~~~~~~~~~~~~~~~~ |
| 499 | |
| 500 | To build asynchronous handlers, use the :class:`ThreadingMixIn` and |
| 501 | :class:`ForkingMixIn` classes. |
| 502 | |
| 503 | An example for the :class:`ThreadingMixIn` class:: |
| 504 | |
| 505 | import socket |
| 506 | import threading |
| 507 | import socketserver |
| 508 | |
| 509 | class ThreadedTCPRequestHandler(socketserver.BaseRequestHandler): |
| 510 | |
| 511 | def handle(self): |
Florent Xicluna | 023611f | 2011-10-23 22:40:37 +0200 | [diff] [blame] | 512 | data = str(self.request.recv(1024), 'ascii') |
Georg Brandl | f992640 | 2008-06-13 06:32:25 +0000 | [diff] [blame] | 513 | cur_thread = threading.current_thread() |
Florent Xicluna | 023611f | 2011-10-23 22:40:37 +0200 | [diff] [blame] | 514 | response = bytes("{}: {}".format(cur_thread.name, data), 'ascii') |
Senthil Kumaran | 6e13f13 | 2012-02-09 17:54:17 +0800 | [diff] [blame] | 515 | self.request.sendall(response) |
Georg Brandl | b533e26 | 2008-05-25 18:19:30 +0000 | [diff] [blame] | 516 | |
| 517 | class ThreadedTCPServer(socketserver.ThreadingMixIn, socketserver.TCPServer): |
| 518 | pass |
| 519 | |
| 520 | def client(ip, port, message): |
| 521 | sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) |
| 522 | sock.connect((ip, port)) |
Florent Xicluna | 023611f | 2011-10-23 22:40:37 +0200 | [diff] [blame] | 523 | try: |
Senthil Kumaran | 6e13f13 | 2012-02-09 17:54:17 +0800 | [diff] [blame] | 524 | sock.sendall(bytes(message, 'ascii')) |
Florent Xicluna | 023611f | 2011-10-23 22:40:37 +0200 | [diff] [blame] | 525 | response = str(sock.recv(1024), 'ascii') |
| 526 | print("Received: {}".format(response)) |
| 527 | finally: |
| 528 | sock.close() |
Georg Brandl | b533e26 | 2008-05-25 18:19:30 +0000 | [diff] [blame] | 529 | |
| 530 | if __name__ == "__main__": |
| 531 | # Port 0 means to select an arbitrary unused port |
| 532 | HOST, PORT = "localhost", 0 |
| 533 | |
| 534 | server = ThreadedTCPServer((HOST, PORT), ThreadedTCPRequestHandler) |
| 535 | ip, port = server.server_address |
| 536 | |
| 537 | # Start a thread with the server -- that thread will then start one |
| 538 | # more thread for each request |
| 539 | server_thread = threading.Thread(target=server.serve_forever) |
| 540 | # Exit the server thread when the main thread terminates |
Florent Xicluna | 023611f | 2011-10-23 22:40:37 +0200 | [diff] [blame] | 541 | server_thread.daemon = True |
Georg Brandl | b533e26 | 2008-05-25 18:19:30 +0000 | [diff] [blame] | 542 | server_thread.start() |
Benjamin Peterson | d75fcb4 | 2009-02-19 04:22:03 +0000 | [diff] [blame] | 543 | print("Server loop running in thread:", server_thread.name) |
Georg Brandl | b533e26 | 2008-05-25 18:19:30 +0000 | [diff] [blame] | 544 | |
Florent Xicluna | 023611f | 2011-10-23 22:40:37 +0200 | [diff] [blame] | 545 | client(ip, port, "Hello World 1") |
| 546 | client(ip, port, "Hello World 2") |
| 547 | client(ip, port, "Hello World 3") |
Georg Brandl | b533e26 | 2008-05-25 18:19:30 +0000 | [diff] [blame] | 548 | |
| 549 | server.shutdown() |
| 550 | |
Benjamin Peterson | 06fd5f8 | 2008-11-08 17:24:34 +0000 | [diff] [blame] | 551 | |
Georg Brandl | b533e26 | 2008-05-25 18:19:30 +0000 | [diff] [blame] | 552 | The output of the example should look something like this:: |
| 553 | |
| 554 | $ python ThreadedTCPServer.py |
| 555 | Server loop running in thread: Thread-1 |
Florent Xicluna | 023611f | 2011-10-23 22:40:37 +0200 | [diff] [blame] | 556 | Received: Thread-2: Hello World 1 |
| 557 | Received: Thread-3: Hello World 2 |
| 558 | Received: Thread-4: Hello World 3 |
Georg Brandl | b533e26 | 2008-05-25 18:19:30 +0000 | [diff] [blame] | 559 | |
| 560 | |
| 561 | The :class:`ForkingMixIn` class is used in the same way, except that the server |
| 562 | will spawn a new process for each request. |