1 <h2>libwebsocket_client_connect - Connect to another websocket server</h2>
2 <i>struct libwebsocket *</i>
3 <b>libwebsocket_client_connect</b>
4 (<i>struct libwebsocket_context *</i> <b>context</b>,
5 <i>const char *</i> <b>address</b>,
6 <i>int</i> <b>port</b>,
7 <i>int</i> <b>ssl_connection</b>,
8 <i>const char *</i> <b>path</b>,
9 <i>const char *</i> <b>host</b>,
10 <i>const char *</i> <b>origin</b>,
11 <i>const char *</i> <b>protocol</b>,
12 <i>int</i> <b>ietf_version_or_minus_one</b>)
18 <dd>Remote server address, eg, "myserver.com"
20 <dd>Port to connect to on the remote server, eg, 80
21 <dt><b>ssl_connection</b>
22 <dd>0 = ws://, 1 = wss:// encrypted, 2 = wss:// allow self
25 <dd>Websocket path on server
27 <dd>Hostname on server
29 <dd>Socket origin name
31 <dd>Comma-separated list of protocols being asked for from
32 the server, or just one. The server will pick the one it
34 <dt><b>ietf_version_or_minus_one</b>
35 <dd>-1 to ask to connect using the default, latest
36 protocol supported, or the specific protocol ordinal
40 This function creates a connection to a remote server
43 <h2>libwebsocket_client_connect_extended - Connect to another websocket server</h2>
44 <i>struct libwebsocket *</i>
45 <b>libwebsocket_client_connect_extended</b>
46 (<i>struct libwebsocket_context *</i> <b>context</b>,
47 <i>const char *</i> <b>address</b>,
48 <i>int</i> <b>port</b>,
49 <i>int</i> <b>ssl_connection</b>,
50 <i>const char *</i> <b>path</b>,
51 <i>const char *</i> <b>host</b>,
52 <i>const char *</i> <b>origin</b>,
53 <i>const char *</i> <b>protocol</b>,
54 <i>int</i> <b>ietf_version_or_minus_one</b>,
55 <i>void *</i> <b>userdata</b>)
61 <dd>Remote server address, eg, "myserver.com"
63 <dd>Port to connect to on the remote server, eg, 80
64 <dt><b>ssl_connection</b>
65 <dd>0 = ws://, 1 = wss:// encrypted, 2 = wss:// allow self
68 <dd>Websocket path on server
70 <dd>Hostname on server
72 <dd>Socket origin name
74 <dd>Comma-separated list of protocols being asked for from
75 the server, or just one. The server will pick the one it
77 <dt><b>ietf_version_or_minus_one</b>
78 <dd>-1 to ask to connect using the default, latest
79 protocol supported, or the specific protocol ordinal
81 <dd>Pre-allocated user data
85 This function creates a connection to a remote server
88 <h2>lws_get_library_version - </h2>
90 <b>lws_get_library_version</b>
100 returns a const char * to a string like "1.1 178d78c"
101 representing the library version followed by the git head hash it
105 <h2>libwebsockets_hangup_on_client - Server calls to terminate client connection</h2>
107 <b>libwebsockets_hangup_on_client</b>
108 (<i>struct libwebsocket_context *</i> <b>context</b>,
109 <i>int</i> <b>fd</b>)
113 <dd>libwebsockets context
115 <dd>Connection socket descriptor
118 <h2>libwebsockets_get_peer_addresses - Get client address information</h2>
120 <b>libwebsockets_get_peer_addresses</b>
121 (<i>struct libwebsocket_context *</i> <b>context</b>,
122 <i>struct libwebsocket *</i> <b>wsi</b>,
123 <i>int</i> <b>fd</b>,
124 <i>char *</i> <b>name</b>,
125 <i>int</i> <b>name_len</b>,
126 <i>char *</i> <b>rip</b>,
127 <i>int</i> <b>rip_len</b>)
131 <dd>Libwebsockets context
133 <dd>Local struct libwebsocket associated with
135 <dd>Connection socket descriptor
137 <dd>Buffer to take client address name
139 <dd>Length of client address name buffer
141 <dd>Buffer to take client address IP qotted quad
143 <dd>Length of client address IP buffer
147 This function fills in <tt><b>name</b></tt> and <tt><b>rip</b></tt> with the name and IP of
148 the client connected with socket descriptor <tt><b>fd</b></tt>. Names may be
149 truncated if there is not enough room. If either cannot be
150 determined, they will be returned as valid zero-length strings.
153 <h2>libwebsocket_service_fd - Service polled socket with something waiting</h2>
155 <b>libwebsocket_service_fd</b>
156 (<i>struct libwebsocket_context *</i> <b>context</b>,
157 <i>struct pollfd *</i> <b>pollfd</b>)
161 <dd>Websocket context
163 <dd>The pollfd entry describing the socket fd and which events
168 This function takes a pollfd that has POLLIN or POLLOUT activity and
169 services it according to the state of the associated struct libwebsocket.
171 The one call deals with all "service" that might happen on a socket
172 including listen accepts, http files as well as websocket protocol.
175 <h2>libwebsocket_context_destroy - Destroy the websocket context</h2>
177 <b>libwebsocket_context_destroy</b>
178 (<i>struct libwebsocket_context *</i> <b>context</b>)
182 <dd>Websocket context
186 This function closes any active connections and then frees the
187 context. After calling this, any further use of the context is
191 <h2>libwebsocket_context_user - get the user data associated with the whole context</h2>
192 <i>LWS_EXTERN void *</i>
193 <b>libwebsocket_context_user</b>
194 (<i>struct libwebsocket_context *</i> <b>context</b>)
198 <dd>Websocket context
202 This returns the optional user allocation that can be attached to
203 the context the sockets live in at context_create time. It's a way
204 to let all sockets serviced in the same context share data without
205 using globals statics in the user code.
208 <h2>libwebsocket_service - Service any pending websocket activity</h2>
210 <b>libwebsocket_service</b>
211 (<i>struct libwebsocket_context *</i> <b>context</b>,
212 <i>int</i> <b>timeout_ms</b>)
216 <dd>Websocket context
217 <dt><b>timeout_ms</b>
218 <dd>Timeout for poll; 0 means return immediately if nothing needed
219 service otherwise block and service immediately, returning
220 after the timeout if nothing needed service.
224 This function deals with any pending websocket traffic, for three
225 kinds of event. It handles these events on both server and client
226 types of connection the same.
228 1) Accept new connections to our context's server
230 2) Call the receive callback for incoming frame data received by
231 server or client connections.
233 You need to call this service function periodically to all the above
234 functions to happen; if your application is single-threaded you can
235 just call it in your main event loop.
237 Alternatively you can fork a new process that asynchronously handles
238 calling this service in a loop. In that case you are happy if this
239 call blocks your thread until it needs to take care of something and
240 would call it with a large nonzero timeout. Your loop then takes no
241 CPU while there is nothing happening.
243 If you are calling it in a single-threaded app, you don't want it to
244 wait around blocking other things in your loop from happening, so you
245 would call it with a timeout_ms of 0, so it returns immediately if
246 nothing is pending, or as soon as it services whatever was pending.
249 <h2>libwebsocket_callback_on_writable - Request a callback when this socket becomes able to be written to without blocking</h2>
251 <b>libwebsocket_callback_on_writable</b>
252 (<i>struct libwebsocket_context *</i> <b>context</b>,
253 <i>struct libwebsocket *</i> <b>wsi</b>)
257 <dd>libwebsockets context
259 <dd>Websocket connection instance to get callback for
262 <h2>libwebsocket_callback_on_writable_all_protocol - Request a callback for all connections using the given protocol when it becomes possible to write to each socket without blocking in turn.</h2>
264 <b>libwebsocket_callback_on_writable_all_protocol</b>
265 (<i>const struct libwebsocket_protocols *</i> <b>protocol</b>)
269 <dd>Protocol whose connections will get callbacks
272 <h2>libwebsocket_set_timeout - marks the wsi as subject to a timeout</h2>
274 <b>libwebsocket_set_timeout</b>
275 (<i>struct libwebsocket *</i> <b>wsi</b>,
276 <i>enum pending_timeout</i> <b>reason</b>,
277 <i>int</i> <b>secs</b>)
281 <dd>Websocket connection instance
290 You will not need this unless you are doing something special
293 <h2>libwebsocket_get_socket_fd - returns the socket file descriptor</h2>
295 <b>libwebsocket_get_socket_fd</b>
296 (<i>struct libwebsocket *</i> <b>wsi</b>)
300 <dd>Websocket connection instance
305 You will not need this unless you are doing something special
308 <h2>libwebsocket_rx_flow_control - Enable and disable socket servicing for receieved packets.</h2>
310 <b>libwebsocket_rx_flow_control</b>
311 (<i>struct libwebsocket *</i> <b>wsi</b>,
312 <i>int</i> <b>enable</b>)
316 <dd>Websocket connection instance to get callback for
318 <dd>0 = disable read servicing for this connection, 1 = enable
323 If the output side of a server process becomes choked, this allows flow
324 control for the input side.
327 <h2>libwebsocket_canonical_hostname - returns this host's hostname</h2>
329 <b>libwebsocket_canonical_hostname</b>
330 (<i>struct libwebsocket_context *</i> <b>context</b>)
334 <dd>Websocket context
339 This is typically used by client code to fill in the host parameter
340 when making a client connection. You can only call it after the context
344 <h2>libwebsocket_create_context - Create the websocket handler</h2>
345 <i>struct libwebsocket_context *</i>
346 <b>libwebsocket_create_context</b>
347 (<i>int</i> <b>port</b>,
348 <i>const char *</i> <b>interf</b>,
349 <i>struct libwebsocket_protocols *</i> <b>protocols</b>,
350 <i>struct libwebsocket_extension *</i> <b>extensions</b>,
351 <i>const char *</i> <b>ssl_cert_filepath</b>,
352 <i>const char *</i> <b>ssl_private_key_filepath</b>,
353 <i>const char *</i> <b>ssl_ca_filepath</b>,
354 <i>int</i> <b>gid</b>,
355 <i>int</i> <b>uid</b>,
356 <i>unsigned int</i> <b>options</b>,
357 <i>void *</i> <b>user</b>)
361 <dd>Port to listen on... you can use 0 to suppress listening on
362 any port, that's what you want if you are not running a
363 websocket server at all but just using it as a client
365 <dd>NULL to bind the listen socket to all interfaces, or the
366 interface name, eg, "eth2"
368 <dd>Array of structures listing supported protocols and a protocol-
369 specific callback for each one. The list is ended with an
370 entry that has a NULL callback pointer.
371 It's not const because we write the owning_server member
372 <dt><b>extensions</b>
373 <dd>NULL or array of libwebsocket_extension structs listing the
374 extensions this context supports. If you configured with
375 --without-extensions, you should give NULL here.
376 <dt><b>ssl_cert_filepath</b>
377 <dd>If libwebsockets was compiled to use ssl, and you want
378 to listen using SSL, set to the filepath to fetch the
379 server cert from, otherwise NULL for unencrypted
380 <dt><b>ssl_private_key_filepath</b>
381 <dd>filepath to private key if wanting SSL mode,
383 <dt><b>ssl_ca_filepath</b>
384 <dd>CA certificate filepath or NULL
386 <dd>group id to change to after setting listen socket, or -1.
388 <dd>user id to change to after setting listen socket, or -1.
390 <dd>0, or LWS_SERVER_OPTION_DEFEAT_CLIENT_MASK
392 <dd>optional user pointer that can be recovered via the context
393 pointer using libwebsocket_context_user
397 This function creates the listening socket and takes care
398 of all initialization in one step.
400 After initialization, it returns a struct libwebsocket_context * that
401 represents this server. After calling, user code needs to take care
402 of calling <b>libwebsocket_service</b> with the context pointer to get the
403 server's sockets serviced. This can be done in the same process context
404 or a forked process, or another thread,
406 The protocol callback functions are called for a handful of events
407 including http requests coming in, websocket connections becoming
408 established, and data arriving; it's also called periodically to allow
411 HTTP requests are sent always to the FIRST protocol in <tt><b>protocol</b></tt>, since
412 at that time websocket protocol has not been negotiated. Other
413 protocols after the first one never see any HTTP callack activity.
415 The server created is a simple http server by default; part of the
416 websocket standard is upgrading this http connection to a websocket one.
418 This allows the same server to provide files like scripts and favicon /
419 images or whatever over http and dynamic data over websockets all in
420 one place; they're all handled in the user callback.
423 <h2>libwebsockets_get_protocol - Returns a protocol pointer from a websocket connection.</h2>
424 <i>const struct libwebsocket_protocols *</i>
425 <b>libwebsockets_get_protocol</b>
426 (<i>struct libwebsocket *</i> <b>wsi</b>)
430 <dd>pointer to struct websocket you want to know the protocol of
435 Some apis can act on all live connections of a given protocol,
436 this is how you can get a pointer to the active protocol if needed.
439 <h2>lws_set_log_level - Set the logging bitfield</h2>
441 <b>lws_set_log_level</b>
442 (<i>int</i> <b>level</b>,
443 <i>void (*</i><b>log_emit_function</b>) <i>(int level, const char *line)</i>)
447 <dd>OR together the LLL_ debug contexts you want output from
448 <dt><b>log_emit_function</b>
449 <dd>NULL to leave it as it is, or a user-supplied
450 function to perform log string emission instead of
451 the default stderr one.
455 log level defaults to "err" and "warn" contexts enabled only and
459 <h2>libwebsocket_write - Apply protocol then write data to client</h2>
461 <b>libwebsocket_write</b>
462 (<i>struct libwebsocket *</i> <b>wsi</b>,
463 <i>unsigned char *</i> <b>buf</b>,
464 <i>size_t</i> <b>len</b>,
465 <i>enum libwebsocket_write_protocol</i> <b>protocol</b>)
469 <dd>Websocket instance (available from user callback)
471 <dd>The data to send. For data being sent on a websocket
472 connection (ie, not default http), this buffer MUST have
473 LWS_SEND_BUFFER_PRE_PADDING bytes valid BEFORE the pointer
474 and an additional LWS_SEND_BUFFER_POST_PADDING bytes valid
475 in the buffer after (buf + len). This is so the protocol
476 header and trailer data can be added in-situ.
478 <dd>Count of the data bytes in the payload starting from buf
480 <dd>Use LWS_WRITE_HTTP to reply to an http connection, and one
481 of LWS_WRITE_BINARY or LWS_WRITE_TEXT to send appropriate
482 data on a websockets connection. Remember to allow the extra
483 bytes before and after buf if LWS_WRITE_BINARY or LWS_WRITE_TEXT
488 This function provides the way to issue data back to the client
489 for both http and websocket protocols.
491 In the case of sending using websocket protocol, be sure to allocate
492 valid storage before and after buf as explained above. This scheme
493 allows maximum efficiency of sending data and protocol in a single
494 packet while not burdening the user code with any protocol knowledge.
497 <h2>libwebsockets_serve_http_file - Send a file back to the client using http</h2>
499 <b>libwebsockets_serve_http_file</b>
500 (<i>struct libwebsocket_context *</i> <b>context</b>,
501 <i>struct libwebsocket *</i> <b>wsi</b>,
502 <i>const char *</i> <b>file</b>,
503 <i>const char *</i> <b>content_type</b>)
507 <dd>libwebsockets context
509 <dd>Websocket instance (available from user callback)
511 <dd>The file to issue over http
512 <dt><b>content_type</b>
513 <dd>The http content type, eg, text/html
517 This function is intended to be called from the callback in response
518 to http requests from the client. It allows the callback to issue
519 local files down the http link in a single step.
522 <h2>lws_frame_is_binary - </h2>
524 <b>lws_frame_is_binary</b>
525 (<i>struct libwebsocket *</i> <b>wsi</b>)
529 <dd>the connection we are inquiring about
533 This is intended to be called from the LWS_CALLBACK_RECEIVE callback if
534 it's interested to see if the frame it's dealing with was sent in binary
538 <h2>libwebsockets_remaining_packet_payload - Bytes to come before "overall" rx packet is complete</h2>
540 <b>libwebsockets_remaining_packet_payload</b>
541 (<i>struct libwebsocket *</i> <b>wsi</b>)
545 <dd>Websocket instance (available from user callback)
549 This function is intended to be called from the callback if the
550 user code is interested in "complete packets" from the client.
551 libwebsockets just passes through payload as it comes and issues a buffer
552 additionally when it hits a built-in limit. The LWS_CALLBACK_RECEIVE
553 callback handler can use this API to find out if the buffer it has just
554 been given is the last piece of a "complete packet" from the client --
555 when that is the case <b>libwebsockets_remaining_packet_payload</b> will return
558 Many protocols won't care becuse their packets are always small.
561 <h2>callback - User server actions</h2>
562 <i>LWS_EXTERN int</i>
564 (<i>struct libwebsocket_context *</i> <b>context</b>,
565 <i>struct libwebsocket *</i> <b>wsi</b>,
566 <i>enum libwebsocket_callback_reasons</i> <b>reason</b>,
567 <i>void *</i> <b>user</b>,
568 <i>void *</i> <b>in</b>,
569 <i>size_t</i> <b>len</b>)
573 <dd>Websockets context
575 <dd>Opaque websocket instance pointer
577 <dd>The reason for the call
579 <dd>Pointer to per-session user data allocated by library
581 <dd>Pointer used for some callback reasons
583 <dd>Length set for some callback reasons
587 This callback is the way the user controls what is served. All the
588 protocol detail is hidden and handled by the library.
590 For each connection / session there is user data allocated that is
591 pointed to by "user". You set the size of this user data area when
592 the library is initialized with libwebsocket_create_server.
594 You get an opportunity to initialize user data when called back with
595 LWS_CALLBACK_ESTABLISHED reason.
597 <h3>LWS_CALLBACK_ESTABLISHED</h3>
599 after the server completes a handshake with
602 <h3>LWS_CALLBACK_CLIENT_CONNECTION_ERROR</h3>
604 the request client connection has
605 been unable to complete a handshake with the remote server
607 <h3>LWS_CALLBACK_CLIENT_FILTER_PRE_ESTABLISH</h3>
609 this is the last chance for the
610 client user code to examine the http headers
611 and decide to reject the connection. If the
612 content in the headers is interesting to the
613 client (url, etc) it needs to copy it out at
614 this point since it will be destroyed before
615 the CLIENT_ESTABLISHED call
617 <h3>LWS_CALLBACK_CLIENT_ESTABLISHED</h3>
619 after your client connection completed
620 a handshake with the remote server
622 <h3>LWS_CALLBACK_CLOSED</h3>
624 when the websocket session ends
626 <h3>LWS_CALLBACK_RECEIVE</h3>
628 data has appeared for this server endpoint from a
629 remote client, it can be found at *in and is
632 <h3>LWS_CALLBACK_CLIENT_RECEIVE_PONG</h3>
634 if you elected to see PONG packets,
635 they appear with this callback reason. PONG
636 packets only exist in 04+ protocol
638 <h3>LWS_CALLBACK_CLIENT_RECEIVE</h3>
640 data has appeared from the server for the
641 client connection, it can be found at *in and
644 <h3>LWS_CALLBACK_HTTP</h3>
646 an http request has come from a client that is not
647 asking to upgrade the connection to a websocket
648 one. This is a chance to serve http content,
649 for example, to send a script to the client
650 which will then open the websockets connection.
651 <tt><b>in</b></tt> points to the URI path requested and
652 <b>libwebsockets_serve_http_file</b> makes it very
653 simple to send back a file to the client.
654 Normally after sending the file you are done
655 with the http connection, since the rest of the
656 activity will come by websockets from the script
657 that was delivered by http, so you will want to
658 return 1; to close and free up the connection.
659 That's important because it uses a slot in the
660 total number of client connections allowed set
663 <h3>LWS_CALLBACK_HTTP_FILE_COMPLETION</h3>
665 a file requested to be send down
666 http link has completed.
668 <h3>LWS_CALLBACK_SERVER_WRITEABLE</h3>
671 <b>libwebsocket_callback_on_writable</b> on a connection, you will
672 get one of these callbacks coming when the connection socket
673 is able to accept another write packet without blocking.
674 If it already was able to take another packet without blocking,
675 you'll get this callback at the next call to the service loop
676 function. Notice that CLIENTs get LWS_CALLBACK_CLIENT_WRITEABLE
677 and servers get LWS_CALLBACK_SERVER_WRITEABLE.
679 <h3>LWS_CALLBACK_FILTER_NETWORK_CONNECTION</h3>
681 called when a client connects to
682 the server at network level; the connection is accepted but then
683 passed to this callback to decide whether to hang up immediately
684 or not, based on the client IP. <tt><b>user</b></tt> contains the connection
685 socket's descriptor. Return non-zero to terminate
686 the connection before sending or receiving anything.
687 Because this happens immediately after the network connection
688 from the client, there's no websocket protocol selected yet so
689 this callback is issued only to protocol 0.
691 <h3>LWS_CALLBACK_FILTER_PROTOCOL_CONNECTION</h3>
693 called when the handshake has
694 been received and parsed from the client, but the response is
695 not sent yet. Return non-zero to disallow the connection.
696 <tt><b>user</b></tt> is a pointer to an array of struct lws_tokens, you can
697 use the header enums lws_token_indexes from libwebsockets.h
698 to check for and read the supported header presence and
699 content before deciding to allow the handshake to proceed or
700 to kill the connection.
702 <h3>LWS_CALLBACK_OPENSSL_LOAD_EXTRA_CLIENT_VERIFY_CERTS</h3>
705 including OpenSSL support, this callback allows your user code
706 to perform extra <b>SSL_CTX_load_verify_locations</b> or similar
707 calls to direct OpenSSL where to find certificates the client
708 can use to confirm the remote server identity. <tt><b>user</b></tt> is the
711 <h3>LWS_CALLBACK_OPENSSL_LOAD_EXTRA_SERVER_VERIFY_CERTS</h3>
714 including OpenSSL support, this callback allows your user code
715 to load extra certifcates into the server which allow it to
716 verify the validity of certificates returned by clients. <tt><b>user</b></tt>
717 is the server's OpenSSL SSL_CTX*
719 <h3>LWS_CALLBACK_OPENSSL_PERFORM_CLIENT_CERT_VERIFICATION</h3>
722 libwebsockets context was created with the option
723 LWS_SERVER_OPTION_REQUIRE_VALID_OPENSSL_CLIENT_CERT, then this
724 callback is generated during OpenSSL verification of the cert
725 sent from the client. It is sent to protocol[0] callback as
726 no protocol has been negotiated on the connection yet.
727 Notice that the libwebsockets context and wsi are both NULL
728 during this callback. See
732 //www.openssl.org/docs/ssl/SSL_CTX_set_verify.html
733 to understand more detail about the OpenSSL callback that
734 generates this libwebsockets callback and the meanings of the
735 arguments passed. In this callback, <tt><b>user</b></tt> is the x509_ctx,
736 <tt><b>in</b></tt> is the ssl pointer and <tt><b>len</b></tt> is preverify_ok
737 Notice that this callback maintains libwebsocket return
738 conventions, return 0 to mean the cert is OK or 1 to fail it.
739 This also means that if you don't handle this callback then
740 the default callback action of returning 0 allows the client
743 <h3>LWS_CALLBACK_CLIENT_APPEND_HANDSHAKE_HEADER</h3>
745 this callback happens
746 when a client handshake is being compiled. <tt><b>user</b></tt> is NULL,
747 <tt><b>in</b></tt> is a char **, it's pointing to a char * which holds the
748 next location in the header buffer where you can add
749 headers, and <tt><b>len</b></tt> is the remaining space in the header buffer,
750 which is typically some hundreds of bytes. So, to add a canned
751 cookie, your handler code might look similar to:
753 char **p = (char **)in;
758 *p += sprintf(*p, "Cookie: a=b\x0d\x0a");
762 Notice if you add anything, you just have to take care about
763 the CRLF on the line you added. Obviously this callback is
764 optional, if you don't handle it everything is fine.
766 Notice the callback is coming to protocols[0] all the time,
767 because there is no specific protocol handshook yet.
769 <h3>LWS_CALLBACK_CONFIRM_EXTENSION_OKAY</h3>
771 When the server handshake code
772 sees that it does support a requested extension, before
773 accepting the extension by additing to the list sent back to
774 the client it gives this callback just to check that it's okay
775 to use that extension. It calls back to the requested protocol
776 and with <tt><b>in</b></tt> being the extension name, <tt><b>len</b></tt> is 0 and <tt><b>user</b></tt> is
777 valid. Note though at this time the ESTABLISHED callback hasn't
778 happened yet so if you initialize <tt><b>user</b></tt> content there, <tt><b>user</b></tt>
779 content during this callback might not be useful for anything.
780 Notice this callback comes to protocols[0].
782 <h3>LWS_CALLBACK_CLIENT_CONFIRM_EXTENSION_SUPPORTED</h3>
785 connection is being prepared to start a handshake to a server,
786 each supported extension is checked with protocols[0] callback
787 with this reason, giving the user code a chance to suppress the
788 claim to support that extension by returning non-zero. If
789 unhandled, by default 0 will be returned and the extension
790 support included in the header to the server. Notice this
791 callback comes to protocols[0].
793 The next four reasons are optional and only need taking care of if you
794 will be integrating libwebsockets sockets into an external polling
797 <h3>LWS_CALLBACK_ADD_POLL_FD</h3>
799 libwebsocket deals with its <b>poll</b> loop
800 internally, but in the case you are integrating with another
801 server you will need to have libwebsocket sockets share a
802 polling array with the other server. This and the other
803 POLL_FD related callbacks let you put your specialized
804 poll array interface code in the callback for protocol 0, the
805 first protocol you support, usually the HTTP protocol in the
806 serving case. This callback happens when a socket needs to be
808 <h3>added to the polling loop</h3>
810 <tt><b>user</b></tt> contains the fd, and
811 <tt><b>len</b></tt> is the events bitmap (like, POLLIN). If you are using the
812 internal polling loop (the "service" callback), you can just
813 ignore these callbacks.
815 <h3>LWS_CALLBACK_DEL_POLL_FD</h3>
817 This callback happens when a socket descriptor
818 needs to be removed from an external polling array. <tt><b>user</b></tt> is
819 the socket desricptor. If you are using the internal polling
820 loop, you can just ignore it.
822 <h3>LWS_CALLBACK_SET_MODE_POLL_FD</h3>
824 This callback happens when libwebsockets
825 wants to modify the events for the socket descriptor in <tt><b>user</b></tt>.
826 The handler should OR <tt><b>len</b></tt> on to the events member of the pollfd
827 struct for this socket descriptor. If you are using the
828 internal polling loop, you can just ignore it.
830 <h3>LWS_CALLBACK_CLEAR_MODE_POLL_FD</h3>
832 This callback occurs when libwebsockets
833 wants to modify the events for the socket descriptor in <tt><b>user</b></tt>.
834 The handler should AND ~<tt><b>len</b></tt> on to the events member of the
835 pollfd struct for this socket descriptor. If you are using the
836 internal polling loop, you can just ignore it.
839 <h2>extension_callback - Hooks to allow extensions to operate</h2>
840 <i>LWS_EXTERN int</i>
841 <b>extension_callback</b>
842 (<i>struct libwebsocket_context *</i> <b>context</b>,
843 <i>struct libwebsocket_extension *</i> <b>ext</b>,
844 <i>struct libwebsocket *</i> <b>wsi</b>,
845 <i>enum libwebsocket_extension_callback_reasons</i> <b>reason</b>,
846 <i>void *</i> <b>user</b>,
847 <i>void *</i> <b>in</b>,
848 <i>size_t</i> <b>len</b>)
852 <dd>Websockets context
856 <dd>Opaque websocket instance pointer
858 <dd>The reason for the call
860 <dd>Pointer to per-session user data allocated by library
862 <dd>Pointer used for some callback reasons
864 <dd>Length set for some callback reasons
868 Each extension that is active on a particular connection receives
869 callbacks during the connection lifetime to allow the extension to
870 operate on websocket data and manage itself.
872 Libwebsockets takes care of allocating and freeing "user" memory for
873 each active extension on each connection. That is what is pointed to
874 by the <tt><b>user</b></tt> parameter.
876 <h3>LWS_EXT_CALLBACK_CONSTRUCT</h3>
878 called when the server has decided to
879 select this extension from the list provided by the client,
880 just before the server will send back the handshake accepting
881 the connection with this extension active. This gives the
882 extension a chance to initialize its connection context found
883 in <tt><b>user</b></tt>.
885 <h3>LWS_EXT_CALLBACK_CLIENT_CONSTRUCT</h3>
887 same as LWS_EXT_CALLBACK_CONSTRUCT
888 but called when client is instantiating this extension. Some
889 extensions will work the same on client and server side and then
890 you can just merge handlers for both CONSTRUCTS.
892 <h3>LWS_EXT_CALLBACK_DESTROY</h3>
894 called when the connection the extension was
895 being used on is about to be closed and deallocated. It's the
896 last chance for the extension to deallocate anything it has
897 allocated in the user data (pointed to by <tt><b>user</b></tt>) before the
898 user data is deleted. This same callback is used whether you
899 are in client or server instantiation context.
901 <h3>LWS_EXT_CALLBACK_PACKET_RX_PREPARSE</h3>
903 when this extension was active on
904 a connection, and a packet of data arrived at the connection,
905 it is passed to this callback to give the extension a chance to
906 change the data, eg, decompress it. <tt><b>user</b></tt> is pointing to the
907 extension's private connection context data, <tt><b>in</b></tt> is pointing
908 to an lws_tokens struct, it consists of a char * pointer called
909 token, and an int called token_len. At entry, these are
910 set to point to the received buffer and set to the content
911 length. If the extension will grow the content, it should use
912 a new buffer allocated in its private user context data and
913 set the pointed-to lws_tokens members to point to its buffer.
915 <h3>LWS_EXT_CALLBACK_PACKET_TX_PRESEND</h3>
917 this works the same way as
918 LWS_EXT_CALLBACK_PACKET_RX_PREPARSE above, except it gives the
919 extension a chance to change websocket data just before it will
920 be sent out. Using the same lws_token pointer scheme in <tt><b>in</b></tt>,
921 the extension can change the buffer and the length to be
922 transmitted how it likes. Again if it wants to grow the
923 buffer safely, it should copy the data into its own buffer and
924 set the lws_tokens token pointer to it.
927 <h2>struct libwebsocket_protocols - List of protocols and handlers server supports.</h2>
928 <b>struct libwebsocket_protocols</b> {<br>
929 <i>const char *</i> <b>name</b>;<br>
930 <i>callback_function *</i> <b>callback</b>;<br>
931 <i>size_t</i> <b>per_session_data_size</b>;<br>
932 <i>struct libwebsocket_context *</i> <b>owning_server</b>;<br>
933 <i>int</i> <b>protocol_index</b>;<br>
938 <dd>Protocol name that must match the one given in the client
939 Javascript new WebSocket(url, 'protocol') name
941 <dd>The service callback used for this protocol. It allows the
942 service action for an entire protocol to be encapsulated in
943 the protocol-specific callback
944 <dt><b>per_session_data_size</b>
945 <dd>Each new connection using this protocol gets
946 this much memory allocated on connection establishment and
947 freed on connection takedown. A pointer to this per-connection
948 allocation is passed into the callback in the 'user' parameter
949 <dt><b>owning_server</b>
950 <dd>the server init call fills in this opaque pointer when
951 registering this protocol with the server.
952 <dt><b>protocol_index</b>
953 <dd>which protocol we are starting from zero
957 This structure represents one protocol supported by the server. An
958 array of these structures is passed to <b>libwebsocket_create_server</b>
959 allows as many protocols as you like to be handled by one server.
962 <h2>struct libwebsocket_extension - An extension we know how to cope with</h2>
963 <b>struct libwebsocket_extension</b> {<br>
964 <i>const char *</i> <b>name</b>;<br>
965 <i>extension_callback_function *</i> <b>callback</b>;<br>
966 <i>size_t</i> <b>per_session_data_size</b>;<br>
967 <i>void *</i> <b>per_context_private_data</b>;<br>
972 <dd>Formal extension name, eg, "deflate-stream"
975 <dt><b>per_session_data_size</b>
976 <dd>Libwebsockets will auto-malloc this much
977 memory for the use of the extension, a pointer
978 to it comes in the <tt><b>user</b></tt> callback parameter
979 <dt><b>per_context_private_data</b>
980 <dd>Optional storage for this externsion that
981 is per-context, so it can track stuff across
982 all sessions, etc, if it wants
projects / platform / upstream / libwebsockets.git / blob