libwebsockets-api-doc.html

<h2>libwebsocket_context_destroy - Destroy the websocket context</h2>
<i>void</i>
<b>libwebsocket_context_destroy</b>
(<i>struct libwebsocket_context *</i> <b>this</b>)
<h3>Arguments</h3>
<dl>
<dt><b>this</b>
<dd>Websocket context
</dl>
<h3>Description</h3>
<blockquote>
This function closes any active connections and then frees the
context.  After calling this, any further use of the context is
undefined.
</blockquote>
<hr>
<h2>libwebsocket_service - Service any pending websocket activity</h2>
<i>int</i>
<b>libwebsocket_service</b>
(<i>struct libwebsocket_context *</i> <b>this</b>,
<i>int</i> <b>timeout_ms</b>)
<h3>Arguments</h3>
<dl>
<dt><b>this</b>
<dd>Websocket context
<dt><b>timeout_ms</b>
<dd>Timeout for poll; 0 means return immediately if nothing needed
service otherwise block and service immediately, returning
after the timeout if nothing needed service.
</dl>
<h3>Description</h3>
<blockquote>
This function deals with any pending websocket traffic, for three
kinds of event.  It handles these events on both server and client
types of connection the same.
<p>
1) Accept new connections to our context's server
<p>
2) Perform pending broadcast writes initiated from other forked
processes (effectively serializing asynchronous broadcasts)
<p>
3) Call the receive callback for incoming frame data received by
server or client connections.
<p>
You need to call this service function periodically to all the above
functions to happen; if your application is single-threaded you can
just call it in your main event loop.
<p>
Alternatively you can fork a new process that asynchronously handles
calling this service in a loop.  In that case you are happy if this
call blocks your thread until it needs to take care of something and
would call it with a large nonzero timeout.  Your loop then takes no
CPU while there is nothing happening.
<p>
If you are calling it in a single-threaded app, you don't want it to
wait around blocking other things in your loop from happening, so you
would call it with a timeout_ms of 0, so it returns immediately if
nothing is pending, or as soon as it services whatever was pending.
</blockquote>
<hr>
<h2>libwebsocket_create_context - Create the websocket handler</h2>
<i>struct libwebsocket_context *</i>
<b>libwebsocket_create_context</b>
(<i>int</i> <b>port</b>,
<i>struct libwebsocket_protocols *</i> <b>protocols</b>,
<i>const char *</i> <b>ssl_cert_filepath</b>,
<i>const char *</i> <b>ssl_private_key_filepath</b>,
<i>int</i> <b>gid</b>,
<i>int</i> <b>uid</b>)
<h3>Arguments</h3>
<dl>
<dt><b>port</b>
<dd>Port to listen on... you can use 0 to suppress listening on
any port, that's what you want if you are not running a
websocket server at all but just using it as a client
<dt><b>protocols</b>
<dd>Array of structures listing supported protocols and a protocol-
specific callback for each one.  The list is ended with an
entry that has a NULL callback pointer.
It's not const because we write the owning_server member
<dt><b>ssl_cert_filepath</b>
<dd>If libwebsockets was compiled to use ssl, and you want
to listen using SSL, set to the filepath to fetch the
server cert from, otherwise NULL for unencrypted
<dt><b>ssl_private_key_filepath</b>
<dd>filepath to private key if wanting SSL mode,
else ignored
<dt><b>gid</b>
<dd>group id to change to after setting listen socket, or -1.
<dt><b>uid</b>
<dd>user id to change to after setting listen socket, or -1.
</dl>
<h3>Description</h3>
<blockquote>
This function creates the listening socket and takes care
of all initialization in one step.
<p>
After initialization, it returns a struct libwebsocket_context * that
represents this server.  After calling, user code needs to take care
of calling <b>libwebsocket_service</b> with the context pointer to get the
server's sockets serviced.  This can be done in the same process context
or a forked process, or another thread,
<p>
The protocol callback functions are called for a handful of events
including http requests coming in, websocket connections becoming
established, and data arriving; it's also called periodically to allow
async transmission.
<p>
HTTP requests are sent always to the FIRST protocol in <tt><b>protocol</b></tt>, since
at that time websocket protocol has not been negotiated.  Other
protocols after the first one never see any HTTP callack activity.
<p>
The server created is a simple http server by default; part of the
websocket standard is upgrading this http connection to a websocket one.
<p>
This allows the same server to provide files like scripts and favicon /
images or whatever over http and dynamic data over websockets all in
one place; they're all handled in the user callback.
</blockquote>
<hr>
<h2>libwebsockets_fork_service_loop - Optional helper function forks off a process for the websocket server loop. You don't have to use this but if not, you have to make sure you are calling libwebsocket_service periodically to service the websocket traffic</h2>
<i>int</i>
<b>libwebsockets_fork_service_loop</b>
(<i>struct libwebsocket_context *</i> <b>this</b>)
<h3>Arguments</h3>
<dl>
<dt><b>this</b>
<dd>server context returned by creation function
</dl>
<hr>
<h2>libwebsockets_get_protocol - Returns a protocol pointer from a websocket connection.</h2>
<i>const struct libwebsocket_protocols *</i>
<b>libwebsockets_get_protocol</b>
(<i>struct libwebsocket *</i> <b>wsi</b>)
<h3>Arguments</h3>
<dl>
<dt><b>wsi</b>
<dd>pointer to struct websocket you want to know the protocol of
</dl>
<h3>Description</h3>
<blockquote>
<p>
This is useful to get the protocol to broadcast back to from inside
the callback.
</blockquote>
<hr>
<h2>libwebsockets_broadcast - Sends a buffer to the callback for all active connections of the given protocol.</h2>
<i>int</i>
<b>libwebsockets_broadcast</b>
(<i>const struct libwebsocket_protocols *</i> <b>protocol</b>,
<i>unsigned char *</i> <b>buf</b>,
<i>size_t</i> <b>len</b>)
<h3>Arguments</h3>
<dl>
<dt><b>protocol</b>
<dd>pointer to the protocol you will broadcast to all members of
<dt><b>buf</b>
<dd>buffer containing the data to be broadcase.  NOTE: this has to be
allocated with LWS_SEND_BUFFER_PRE_PADDING valid bytes before
the pointer and LWS_SEND_BUFFER_POST_PADDING afterwards in the
case you are calling this function from callback context.
<dt><b>len</b>
<dd>length of payload data in buf, starting from buf.
</dl>
<h3>Description</h3>
<blockquote>
This function allows bulk sending of a packet to every connection using
the given protocol.  It does not send the data directly; instead it calls
the callback with a reason type of LWS_CALLBACK_BROADCAST.  If the callback
wants to actually send the data for that connection, the callback itself
should call <b>libwebsocket_write</b>.
<p>
<b>libwebsockets_broadcast</b> can be called from another fork context without
having to take any care about data visibility between the processes, it'll
"just work".
</blockquote>
<hr>
<h2>libwebsocket_write - Apply protocol then write data to client</h2>
<i>int</i>
<b>libwebsocket_write</b>
(<i>struct libwebsocket *</i> <b>wsi</b>,
<i>unsigned char *</i> <b>buf</b>,
<i>size_t</i> <b>len</b>,
<i>enum libwebsocket_write_protocol</i> <b>protocol</b>)
<h3>Arguments</h3>
<dl>
<dt><b>wsi</b>
<dd>Websocket instance (available from user callback)
<dt><b>buf</b>
<dd>The data to send.  For data being sent on a websocket
connection (ie, not default http), this buffer MUST have
LWS_SEND_BUFFER_PRE_PADDING bytes valid BEFORE the pointer
and an additional LWS_SEND_BUFFER_POST_PADDING bytes valid
in the buffer after (buf + len).  This is so the protocol
header and trailer data can be added in-situ.
<dt><b>len</b>
<dd>Count of the data bytes in the payload starting from buf
<dt><b>protocol</b>
<dd>Use LWS_WRITE_HTTP to reply to an http connection, and one
of LWS_WRITE_BINARY or LWS_WRITE_TEXT to send appropriate
data on a websockets connection.  Remember to allow the extra
bytes before and after buf if LWS_WRITE_BINARY or LWS_WRITE_TEXT
are used.
</dl>
<h3>Description</h3>
<blockquote>
This function provides the way to issue data back to the client
for both http and websocket protocols.
<p>
In the case of sending using websocket protocol, be sure to allocate
valid storage before and after buf as explained above.  This scheme
allows maximum efficiency of sending data and protocol in a single
packet while not burdening the user code with any protocol knowledge.
</blockquote>
<hr>
<h2>libwebsockets_serve_http_file - Send a file back to the client using http</h2>
<i>int</i>
<b>libwebsockets_serve_http_file</b>
(<i>struct libwebsocket *</i> <b>wsi</b>,
<i>const char *</i> <b>file</b>,
<i>const char *</i> <b>content_type</b>)
<h3>Arguments</h3>
<dl>
<dt><b>wsi</b>
<dd>Websocket instance (available from user callback)
<dt><b>file</b>
<dd>The file to issue over http
<dt><b>content_type</b>
<dd>The http content type, eg, text/html
</dl>
<h3>Description</h3>
<blockquote>
This function is intended to be called from the callback in response
to http requests from the client.  It allows the callback to issue
local files down the http link in a single step.
</blockquote>
<hr>
<h2>libwebsockets_remaining_packet_payload - Bytes to come before "overall" rx packet is complete</h2>
<i>size_t</i>
<b>libwebsockets_remaining_packet_payload</b>
(<i>struct libwebsocket *</i> <b>wsi</b>)
<h3>Arguments</h3>
<dl>
<dt><b>wsi</b>
<dd>Websocket instance (available from user callback)
</dl>
<h3>Description</h3>
<blockquote>
This function is intended to be called from the callback if the
user code is interested in "complete packets" from the client.
libwebsockets just passes through payload as it comes and issues a buffer
additionally when it hits a built-in limit.  The LWS_CALLBACK_RECEIVE
callback handler can use this API to find out if the buffer it has just
been given is the last piece of a "complete packet" from the client --
when that is the case <b>libwebsockets_remaining_packet_payload</b> will return
0.
<p>
Many protocols won't care becuse their packets are always small.
</blockquote>
<hr>
<h2>callback - User server actions</h2>
<i>int</i>
<b>callback</b>
(<i>struct libwebsocket *</i> <b>wsi</b>,
<i>enum libwebsocket_callback_reasons</i> <b>reason</b>,
<i>void *</i> <b>user</b>,
<i>void *</i> <b>in</b>,
<i>size_t</i> <b>len</b>)
<h3>Arguments</h3>
<dl>
<dt><b>wsi</b>
<dd>Opaque websocket instance pointer
<dt><b>reason</b>
<dd>The reason for the call
<dt><b>user</b>
<dd>Pointer to per-session user data allocated by library
<dt><b>in</b>
<dd>Pointer used for some callback reasons
<dt><b>len</b>
<dd>Length set for some callback reasons
</dl>
<h3>Description</h3>
<blockquote>
This callback is the way the user controls what is served.  All the
protocol detail is hidden and handled by the library.
<p>
For each connection / session there is user data allocated that is
pointed to by "user".  You set the size of this user data area when
the library is initialized with libwebsocket_create_server.
<p>
You get an opportunity to initialize user data when called back with
LWS_CALLBACK_ESTABLISHED reason.
</blockquote>
<h3>LWS_CALLBACK_ESTABLISHED</h3>
<blockquote>
after successful websocket handshake
</blockquote>
<h3>LWS_CALLBACK_CLOSED</h3>
<blockquote>
when the websocket session ends
</blockquote>
<h3>LWS_CALLBACK_BROADCAST</h3>
<blockquote>
signal to send to client (you would use
<b>libwebsocket_write</b> taking care about the
special buffer requirements
</blockquote>
<h3>LWS_CALLBACK_RECEIVE</h3>
<blockquote>
data has appeared for the server, it can be
found at *in and is len bytes long
</blockquote>
<h3>LWS_CALLBACK_HTTP</h3>
<blockquote>
an http request has come from a client that is not
asking to upgrade the connection to a websocket
one.  This is a chance to serve http content,
for example, to send a script to the client
which will then open the websockets connection.
<tt><b>in</b></tt> points to the URI path requested and 
<b>libwebsockets_serve_http_file</b> makes it very
simple to send back a file to the client.
</blockquote>
<hr>
<h2>struct libwebsocket_protocols - List of protocols and handlers server supports.</h2>
<b>struct libwebsocket_protocols</b> {<br>
&nbsp; &nbsp; <i>const char *</i> <b>name</b>;<br>
&nbsp; &nbsp; <i>int (*</i><b>callback</b>) <i>(struct libwebsocket *wsi,enum libwebsocket_callback_reasons reason, void *user,void *in, size_t len)</i>;<br>
&nbsp; &nbsp; <i>size_t</i> <b>per_session_data_size</b>;<br>
&nbsp; &nbsp; <i>struct libwebsocket_context *</i> <b>owning_server</b>;<br>
&nbsp; &nbsp; <i>int</i> <b>broadcast_socket_port</b>;<br>
&nbsp; &nbsp; <i>int</i> <b>broadcast_socket_user_fd</b>;<br>
&nbsp; &nbsp; <i>int</i> <b>protocol_index</b>;<br>
};<br>
<h3>Members</h3>
<dl>
<dt><b>name</b>
<dd>Protocol name that must match the one given in the client
Javascript new WebSocket(url, 'protocol') name
<dt><b>callback</b>
<dd>The service callback used for this protocol.  It allows the
service action for an entire protocol to be encapsulated in
the protocol-specific callback
<dt><b>per_session_data_size</b>
<dd>Each new connection using this protocol gets
this much memory allocated on connection establishment and
freed on connection takedown.  A pointer to this per-connection
allocation is passed into the callback in the 'user' parameter
<dt><b>owning_server</b>
<dd>the server init call fills in this opaque pointer when
registering this protocol with the server.
<dt><b>broadcast_socket_port</b>
<dd>the server init call fills this in with the
localhost port number used to forward broadcasts for this
protocol
<dt><b>broadcast_socket_user_fd</b>
<dd>the server init call fills this in ... the <b>main</b>
process context can write to this socket to perform broadcasts
(use the <b>libwebsockets_broadcast</b> api to do this instead,
it works from any process context)
<dt><b>protocol_index</b>
<dd>which protocol we are starting from zero
</dl>
<h3>Description</h3>
<blockquote>
This structure represents one protocol supported by the server.  An
array of these structures is passed to <b>libwebsocket_create_server</b>
allows as many protocols as you like to be handled by one server.
</blockquote>
<hr>