libwebsockets-api-doc.html

<h2>lws_client_reset - retarget a connected wsi to start over with a new connection (ie, redirect) this only works if still in HTTP, ie, not upgraded yet</h2>
<i>struct lws *</i>
<b>lws_client_reset</b>
(<i>struct lws *</i> <b>wsi</b>,
<i>int</i> <b>ssl</b>,
<i>const char *</i> <b>address</b>,
<i>int</i> <b>port</b>,
<i>const char *</i> <b>path</b>,
<i>const char *</i> <b>host</b>)
<h3>Arguments</h3>
<dl>
</dl>
<h3>wsi</h3>
<blockquote>
connection to reset
</blockquote>
<h3>address</h3>
<blockquote>
network address of the new server
</blockquote>
<h3>port</h3>
<blockquote>
port to connect to
</blockquote>
<h3>path</h3>
<blockquote>
uri path to connect to on the new server
</blockquote>
<h3>host</h3>
<blockquote>
host header to send to the new server
</blockquote>
<hr>
<h2>lws_client_connect_via_info - Connect to another websocket server</h2>
<i>struct lws *</i>
<b>lws_client_connect_via_info</b>
(<i>struct lws_client_connect_info *</i> <b>i</b>)
<h3>Arguments</h3>
<dl>
<dt><b>i</b>
<dd>pointer to lws_client_connect_info struct
</dl>
<h3>Description</h3>
<blockquote>
This function creates a connection to a remote server
</blockquote>
<hr>
<h2>lws_client_connect_extended - Connect to another websocket server DEPRECATED use lws_client_connect_via_info</h2>
<i>struct lws *</i>
<b>lws_client_connect_extended</b>
(<i>struct lws_context *</i> <b>context</b>,
<i>const char *</i> <b>address</b>,
<i>int</i> <b>port</b>,
<i>int</i> <b>ssl_connection</b>,
<i>const char *</i> <b>path</b>,
<i>const char *</i> <b>host</b>,
<i>const char *</i> <b>origin</b>,
<i>const char *</i> <b>protocol</b>,
<i>int</i> <b>ietf_version_or_minus_one</b>,
<i>void *</i> <b>userdata</b>)
<h3>Arguments</h3>
<dl>
<dt><b>context</b>
<dd>Websocket context
<dt><b>address</b>
<dd>Remote server address, eg, "myserver.com"
<dt><b>port</b>
<dd>Port to connect to on the remote server, eg, 80
<dt><b>ssl_connection</b>
<dd>0 = ws://, 1 = wss:// encrypted, 2 = wss:// allow self
signed certs
<dt><b>path</b>
<dd>Websocket path on server
<dt><b>host</b>
<dd>Hostname on server
<dt><b>origin</b>
<dd>Socket origin name
<dt><b>protocol</b>
<dd>Comma-separated list of protocols being asked for from
the server, or just one.  The server will pick the one it
likes best.
<dt><b>ietf_version_or_minus_one</b>
<dd>-1 to ask to connect using the default, latest
protocol supported, or the specific protocol ordinal
<dt><b>userdata</b>
<dd>Pre-allocated user data
</dl>
<h3>Description</h3>
<blockquote>
This function creates a connection to a remote server
</blockquote>
<hr>
<h2>lws_client_connect - Connect to another websocket server DEPRECATED use lws_client_connect_via_info</h2>
<i>struct lws *</i>
<b>lws_client_connect</b>
(<i>struct lws_context *</i> <b>context</b>,
<i>const char *</i> <b>address</b>,
<i>int</i> <b>port</b>,
<i>int</i> <b>ssl_connection</b>,
<i>const char *</i> <b>path</b>,
<i>const char *</i> <b>host</b>,
<i>const char *</i> <b>origin</b>,
<i>const char *</i> <b>protocol</b>,
<i>int</i> <b>ietf_version_or_minus_one</b>)
<h3>Arguments</h3>
<dl>
<dt><b>context</b>
<dd>Websocket context
<dt><b>address</b>
<dd>Remote server address, eg, "myserver.com"
<dt><b>port</b>
<dd>Port to connect to on the remote server, eg, 80
<dt><b>ssl_connection</b>
<dd>0 = ws://, 1 = wss:// encrypted, 2 = wss:// allow self
signed certs
<dt><b>path</b>
<dd>Websocket path on server
<dt><b>host</b>
<dd>Hostname on server
<dt><b>origin</b>
<dd>Socket origin name
<dt><b>protocol</b>
<dd>Comma-separated list of protocols being asked for from
the server, or just one.  The server will pick the one it
likes best.  If you don't want to specify a protocol, which is
legal, use NULL here.
<dt><b>ietf_version_or_minus_one</b>
<dd>-1 to ask to connect using the default, latest
protocol supported, or the specific protocol ordinal
</dl>
<h3>Description</h3>
<blockquote>
This function creates a connection to a remote server
</blockquote>
<hr>
<h2>lws_http_transaction_completed_client - wait for new http transaction or close</h2>
<i>int LWS_WARN_UNUSED_RESULT</i>
<b>lws_http_transaction_completed_client</b>
(<i>struct lws *</i> <b>wsi</b>)
<h3>Arguments</h3>
<dl>
<dt><b>wsi</b>
<dd>websocket connection
</dl>
<h3>Description</h3>
<blockquote>
Returns 1 if the HTTP connection must close now
Returns 0 and resets connection to wait for new HTTP header /
transaction if possible
</blockquote>
<hr>
<h2>lws_get_library_version - </h2>
<i>const char *</i>
<b>lws_get_library_version</b>
(<i></i> <b>void</b>)
<h3>Arguments</h3>
<dl>
<dt><b>void</b>
<dd>no arguments
</dl>
<h3>Description</h3>
<blockquote>
<p>
returns a const char * to a string like "1.1 178d78c"
representing the library version followed by the git head hash it
was built from
</blockquote>
<hr>
<h2>lws_create_context - Create the websocket handler</h2>
<i>struct lws_context *</i>
<b>lws_create_context</b>
(<i>struct lws_context_creation_info *</i> <b>info</b>)
<h3>Arguments</h3>
<dl>
<dt><b>info</b>
<dd>pointer to struct with parameters
</dl>
<h3>Description</h3>
<blockquote>
This function creates the listening socket (if serving) and takes care
of all initialization in one step.
<p>
After initialization, it returns a struct lws_context * that
represents this server.  After calling, user code needs to take care
of calling <b>lws_service</b> with the context pointer to get the
server's sockets serviced.  This must be done in the same process
context as the initialization call.
<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>lws_context_destroy - Destroy the websocket context</h2>
<i>void</i>
<b>lws_context_destroy</b>
(<i>struct lws_context *</i> <b>context</b>)
<h3>Arguments</h3>
<dl>
<dt><b>context</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>lws_return_http_status - Return simple http status</h2>
<i>int</i>
<b>lws_return_http_status</b>
(<i>struct lws *</i> <b>wsi</b>,
<i>unsigned int</i> <b>code</b>,
<i>const char *</i> <b>html_body</b>)
<h3>Arguments</h3>
<dl>
<dt><b>wsi</b>
<dd>Websocket instance (available from user callback)
<dt><b>code</b>
<dd>Status index, eg, 404
<dt><b>html_body</b>
<dd>User-readable HTML description &lt; 1KB, or NULL
</dl>
<h3>Description</h3>
<blockquote>
Helper to report HTTP errors back to the client cleanly and
consistently
</blockquote>
<hr>
<h2>lws_set_timeout - marks the wsi as subject to a timeout</h2>
<i>void</i>
<b>lws_set_timeout</b>
(<i>struct lws *</i> <b>wsi</b>,
<i>enum pending_timeout</i> <b>reason</b>,
<i>int</i> <b>secs</b>)
<h3>Arguments</h3>
<dl>
<dt><b>wsi</b>
<dd>Websocket connection instance
<dt><b>reason</b>
<dd>timeout reason
<dt><b>secs</b>
<dd>how many seconds
</dl>
<h3>Description</h3>
<blockquote>
<p>
You will not need this unless you are doing something special
</blockquote>
<hr>
<h2>lws_get_peer_addresses - Get client address information</h2>
<i>void</i>
<b>lws_get_peer_addresses</b>
(<i>struct lws *</i> <b>wsi</b>,
<i>lws_sockfd_type</i> <b>fd</b>,
<i>char *</i> <b>name</b>,
<i>int</i> <b>name_len</b>,
<i>char *</i> <b>rip</b>,
<i>int</i> <b>rip_len</b>)
<h3>Arguments</h3>
<dl>
<dt><b>wsi</b>
<dd>Local struct lws associated with
<dt><b>fd</b>
<dd>Connection socket descriptor
<dt><b>name</b>
<dd>Buffer to take client address name
<dt><b>name_len</b>
<dd>Length of client address name buffer
<dt><b>rip</b>
<dd>Buffer to take client address IP dotted quad
<dt><b>rip_len</b>
<dd>Length of client address IP buffer
</dl>
<h3>Description</h3>
<blockquote>
This function fills in <tt><b>name</b></tt> and <tt><b>rip</b></tt> with the name and IP of
the client connected with socket descriptor <tt><b>fd</b></tt>.  Names may be
truncated if there is not enough room.  If either cannot be
determined, they will be returned as valid zero-length strings.
</blockquote>
<hr>
<h2>lws_context_user - get the user data associated with the context</h2>
<i>LWS_EXTERN void *</i>
<b>lws_context_user</b>
(<i>struct lws_context *</i> <b>context</b>)
<h3>Arguments</h3>
<dl>
<dt><b>context</b>
<dd>Websocket context
</dl>
<h3>Description</h3>
<blockquote>
This returns the optional user allocation that can be attached to
the context the sockets live in at context_create time.  It's a way
to let all sockets serviced in the same context share data without
using globals statics in the user code.
</blockquote>
<hr>
<h2>lws_callback_all_protocol - Callback all connections using the given protocol with the given reason</h2>
<i>int</i>
<b>lws_callback_all_protocol</b>
(<i>struct lws_context *</i> <b>context</b>,
<i>const struct lws_protocols *</i> <b>protocol</b>,
<i>int</i> <b>reason</b>)
<h3>Arguments</h3>
<dl>
<dt><b>protocol</b>
<dd>Protocol whose connections will get callbacks
<dt><b>reason</b>
<dd>Callback reason index
</dl>
<hr>
<h2>lws_get_socket_fd - returns the socket file descriptor</h2>
<i>int</i>
<b>lws_get_socket_fd</b>
(<i>struct lws *</i> <b>wsi</b>)
<h3>Arguments</h3>
<dl>
<dt><b>wsi</b>
<dd>Websocket connection instance
</dl>
<h3>Description</h3>
<blockquote>
<p>
You will not need this unless you are doing something special
</blockquote>
<hr>
<h2>lws_rx_flow_control - Enable and disable socket servicing for received packets.</h2>
<i>int</i>
<b>lws_rx_flow_control</b>
(<i>struct lws *</i> <b>wsi</b>,
<i>int</i> <b>enable</b>)
<h3>Arguments</h3>
<dl>
<dt><b>wsi</b>
<dd>Websocket connection instance to get callback for
<dt><b>enable</b>
<dd>0 = disable read servicing for this connection, 1 = enable
</dl>
<h3>Description</h3>
<blockquote>
<p>
If the output side of a server process becomes choked, this allows flow
control for the input side.
</blockquote>
<hr>
<h2>lws_rx_flow_allow_all_protocol - Allow all connections with this protocol to receive</h2>
<i>void</i>
<b>lws_rx_flow_allow_all_protocol</b>
(<i>const struct lws_context *</i> <b>context</b>,
<i>const struct lws_protocols *</i> <b>protocol</b>)
<h3>Arguments</h3>
<dl>
<dt><b>protocol</b>
<dd>all connections using this protocol will be allowed to receive
</dl>
<h3>Description</h3>
<blockquote>
<p>
When the user server code realizes it can accept more input, it can
call this to have the RX flow restriction removed from all connections using
the given protocol.
</blockquote>
<hr>
<h2>lws_canonical_hostname - returns this host's hostname</h2>
<i>const char *</i>
<b>lws_canonical_hostname</b>
(<i>struct lws_context *</i> <b>context</b>)
<h3>Arguments</h3>
<dl>
<dt><b>context</b>
<dd>Websocket context
</dl>
<h3>Description</h3>
<blockquote>
<p>
This is typically used by client code to fill in the host parameter
when making a client connection.  You can only call it after the context
has been created.
</blockquote>
<hr>
<h2>lws_set_proxy - Setups proxy to lws_context.</h2>
<i>int</i>
<b>lws_set_proxy</b>
(<i>struct lws_context *</i> <b>context</b>,
<i>const char *</i> <b>proxy</b>)
<h3>Arguments</h3>
<dl>
<dt><b>context</b>
<dd>pointer to struct lws_context you want set proxy to
<dt><b>proxy</b>
<dd>pointer to c string containing proxy in format address:port
</dl>
<h3>Description</h3>
<blockquote>
Returns 0 if proxy string was parsed and proxy was setup.
Returns -1 if <tt><b>proxy</b></tt> is NULL or has incorrect format.
<p>
This is only required if your OS does not provide the http_proxy
environment variable (eg, OSX)
<p>
IMPORTANT! You should call this function right after creation of the
lws_context and before call to connect. If you call this
function after connect behavior is undefined.
This function will override proxy settings made on lws_context
creation with <b>genenv</b> call.
</blockquote>
<hr>
<h2>lws_get_protocol - Returns a protocol pointer from a websocket connection.</h2>
<i>const struct lws_protocols *</i>
<b>lws_get_protocol</b>
(<i>struct lws *</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>
Some apis can act on all live connections of a given protocol,
this is how you can get a pointer to the active protocol if needed.
</blockquote>
<hr>
<h2>lwsl_timestamp - </h2>
<i>int</i>
<b>lwsl_timestamp</b>
(<i>int</i> <b>level</b>,
<i>char *</i> <b>p</b>,
<i>int</i> <b>len</b>)
<h3>Arguments</h3>
<dl>
<dt><b>level</b>
<dd>logging level
<dt><b>p</b>
<dd>char * buffer to take timestamp
<dt><b>len</b>
<dd>length of p
</dl>
<h3>Description</h3>
<blockquote>
returns length written in p
</blockquote>
<hr>
<h2>lws_set_log_level - Set the logging bitfield</h2>
<i>void</i>
<b>lws_set_log_level</b>
(<i>int</i> <b>level</b>,
<i>void (*</i><b>func</b>) <i>(int level, const char *line)</i>)
<h3>Arguments</h3>
<dl>
<dt><b>level</b>
<dd>OR together the LLL_ debug contexts you want output from
</dl>
<h3>Description</h3>
<blockquote>
log level defaults to "err", "warn" and "notice" contexts enabled and
emission on stderr.
</blockquote>
<hr>
<h2>lws_is_ssl - Find out if connection is using SSL</h2>
<i>int</i>
<b>lws_is_ssl</b>
(<i>struct lws *</i> <b>wsi</b>)
<h3>Arguments</h3>
<dl>
<dt><b>wsi</b>
<dd>websocket connection to check
</dl>
<h3>Description</h3>
<blockquote>
Returns 0 if the connection is not using SSL, 1 if using SSL and
using verified cert, and 2 if using SSL but the cert was not
checked (appears for client wsi told to skip check on connection)
</blockquote>
<hr>
<h2>lws_partial_buffered - find out if lws buffered the last write</h2>
<i>int</i>
<b>lws_partial_buffered</b>
(<i>struct lws *</i> <b>wsi</b>)
<h3>Arguments</h3>
<dl>
<dt><b>wsi</b>
<dd>websocket connection to check
</dl>
<h3>Description</h3>
<blockquote>
Returns 1 if you cannot use lws_write because the last
write on this connection is still buffered, and can't be cleared without
returning to the service loop and waiting for the connection to be
writeable again.
<p>
If you will try to do &gt;1 lws_write call inside a single
WRITEABLE callback, you must check this after every write and bail if
set, ask for a new writeable callback and continue writing from there.
<p>
This is never set at the start of a writeable callback, but any write
may set it.
</blockquote>
<hr>
<h2>lws_parse_uri - </h2>
<i>LWS_EXTERN int</i>
<b>lws_parse_uri</b>
(<i>char *</i> <b>p</b>,
<i>const char **</i> <b>prot</b>,
<i>const char **</i> <b>ads</b>,
<i>int *</i> <b>port</b>,
<i>const char **</i> <b>path</b>)
<h3>Arguments</h3>
<dl>
<dt><b>p</b>
<dd>incoming uri string.. will get written to
<dt><b>prot</b>
<dd>result pointer for protocol part (https://)
<dt><b>ads</b>
<dd>result pointer for address part
<dt><b>port</b>
<dd>result pointer for port part
<dt><b>path</b>
<dd>result pointer for path part
</dl>
<h3>Description</h3>
<blockquote>
Notice it does so by dropping '\0' into input string
and the leading / on the path is consequently lost
</blockquote>
<hr>
<h2>lws_cgi - connected cgi process</h2>
<i>LWS_EXTERN int</i>
<b>lws_cgi</b>
(<i>struct lws *</i> <b>wsi</b>,
<i>char *const *</i> <b>exec_array</b>,
<i>int</i> <b>timeout_secs</b>)
<h3>Arguments</h3>
<dl>
<dt><b>wsi</b>
<dd>connection to own the process
<dt><b>exec_array</b>
<dd>array of "exec-name" "arg1" ... "argn" NULL
</dl>
<hr>
<h2>lws_cgi_kill - </h2>
<i>LWS_EXTERN int</i>
<b>lws_cgi_kill</b>
(<i>struct lws *</i> <b>wsi</b>)
<h3>Arguments</h3>
<dl>
<dt><b>wsi</b>
<dd>connection to own the process
</dl>
<hr>
<h2>lws_cancel_service - Cancel servicing of pending websocket activity</h2>
<i>void</i>
<b>lws_cancel_service</b>
(<i>struct lws_context *</i> <b>context</b>)
<h3>Arguments</h3>
<dl>
<dt><b>context</b>
<dd>Websocket context
</dl>
<h3>Description</h3>
<blockquote>
This function let a call to <b>lws_service</b> waiting for a timeout
immediately return.
<p>
There is no <b>poll</b> in MBED3, he will fire callbacks when he feels like
it.
</blockquote>
<hr>
<h2>lws_cancel_service_pt - Cancel servicing of pending socket activity on one thread</h2>
<i>void</i>
<b>lws_cancel_service_pt</b>
(<i>struct lws *</i> <b>wsi</b>)
<h3>Arguments</h3>
<dl>
<dt><b>wsi</b>
<dd>Cancel service on the thread this wsi is serviced by
</dl>
<h3>Description</h3>
<blockquote>
This function let a call to <b>lws_service</b> waiting for a timeout
immediately return.
</blockquote>
<hr>
<h2>lws_cancel_service - Cancel ALL servicing of pending socket activity</h2>
<i>void</i>
<b>lws_cancel_service</b>
(<i>struct lws_context *</i> <b>context</b>)
<h3>Arguments</h3>
<dl>
<dt><b>context</b>
<dd>Websocket context
</dl>
<h3>Description</h3>
<blockquote>
This function let a call to <b>lws_service</b> waiting for a timeout
immediately return.
</blockquote>
<hr>
<h2>lws_cancel_service - Cancel servicing of pending websocket activity</h2>
<i>void</i>
<b>lws_cancel_service</b>
(<i>struct lws_context *</i> <b>context</b>)
<h3>Arguments</h3>
<dl>
<dt><b>context</b>
<dd>Websocket context
</dl>
<h3>Description</h3>
<blockquote>
This function let a call to <b>lws_service</b> waiting for a timeout
immediately return.
</blockquote>
<hr>
<h2>lws_write - Apply protocol then write data to client</h2>
<i>int</i>
<b>lws_write</b>
(<i>struct lws *</i> <b>wsi</b>,
<i>unsigned char *</i> <b>buf</b>,
<i>size_t</i> <b>len</b>,
<i>enum lws_write_protocol</i> <b>wp</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_PRE bytes valid BEFORE the pointer.
This is so the protocol header data can be added in-situ.
<dt><b>len</b>
<dd>Count of the data bytes in the payload starting from buf
</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.
<p>
Return may be -1 for a fatal error needing connection close, or a
positive number reflecting the amount of bytes actually sent.  This
can be less than the requested number of bytes due to OS memory
pressure at any given time.
</blockquote>
<hr>
<h2>lws_hdr_fragment_length - </h2>
<i>int</i>
<b>lws_hdr_fragment_length</b>
(<i>struct lws *</i> <b>wsi</b>,
<i>enum lws_token_indexes</i> <b>h</b>,
<i>int</i> <b>frag_idx</b>)
<h3>Arguments</h3>
<dl>
<dt><b>wsi</b>
<dd>websocket connection
<dt><b>h</b>
<dd>which header index we are interested in
<dt><b>frag_idx</b>
<dd>which fragment of <tt><b>h</b></tt> we want to get the length of
</dl>
<h3>Description</h3>
<blockquote>
The returned length does not include the space for a
terminating '\0'
</blockquote>
<hr>
<h2>lws_hdr_total_length - </h2>
<i>int</i>
<b>lws_hdr_total_length</b>
(<i>struct lws *</i> <b>wsi</b>,
<i>enum lws_token_indexes</i> <b>h</b>)
<h3>Arguments</h3>
<dl>
<dt><b>wsi</b>
<dd>websocket connection
<dt><b>h</b>
<dd>which header index we are interested in
</dl>
<h3>Description</h3>
<blockquote>
The returned length does not include the space for a
terminating '\0'
</blockquote>
<hr>
<h2>lws_hdr_copy_fragment - </h2>
<i>int</i>
<b>lws_hdr_copy_fragment</b>
(<i>struct lws *</i> <b>wsi</b>,
<i>char *</i> <b>dst</b>,
<i>int</i> <b>len</b>,
<i>enum lws_token_indexes</i> <b>h</b>,
<i>int</i> <b>frag_idx</b>)
<h3>Arguments</h3>
<dl>
<dt><b>wsi</b>
<dd>websocket connection
<dt><b>dst</b>
<dd>destination buffer
<dt><b>len</b>
<dd>length of destination buffer
<dt><b>h</b>
<dd>which header index we are interested in
</dl>
<h3>Description</h3>
<blockquote>
The buffer length <tt><b>len</b></tt> must include space for an additional
terminating '\0', or it will fail returning -1.
If the requested fragment index is not present, it fails
returning -1.
</blockquote>
<hr>
<h2>lws_hdr_copy - </h2>
<i>int</i>
<b>lws_hdr_copy</b>
(<i>struct lws *</i> <b>wsi</b>,
<i>char *</i> <b>dst</b>,
<i>int</i> <b>len</b>,
<i>enum lws_token_indexes</i> <b>h</b>)
<h3>Arguments</h3>
<dl>
<dt><b>wsi</b>
<dd>websocket connection
<dt><b>dst</b>
<dd>destination buffer
<dt><b>len</b>
<dd>length of destination buffer
<dt><b>h</b>
<dd>which header index we are interested in
</dl>
<h3>Description</h3>
<blockquote>
The buffer length <tt><b>len</b></tt> must include space for an additional
terminating '\0', or it will fail returning -1.
</blockquote>
<hr>
<h2>lws_frame_is_binary - </h2>
<i>int</i>
<b>lws_frame_is_binary</b>
(<i>struct lws *</i> <b>wsi</b>)
<h3>Arguments</h3>
<dl>
<dt><b>wsi</b>
<dd>the connection we are inquiring about
</dl>
<h3>Description</h3>
<blockquote>
This is intended to be called from the LWS_CALLBACK_RECEIVE callback if
it's interested to see if the frame it's dealing with was sent in binary
mode.
</blockquote>
<hr>
<h2>lws_remaining_packet_payload - Bytes to come before "overall" rx packet is complete</h2>
<i>size_t</i>
<b>lws_remaining_packet_payload</b>
(<i>struct lws *</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>lws_remaining_packet_payload</b> will return
0.
<p>
Many protocols won't care becuse their packets are always small.
</blockquote>
<hr>
<h2>lws_callback_on_writable - Request a callback when this socket becomes able to be written to without blocking</h2>
<i>int</i>
<b>lws_callback_on_writable</b>
(<i>struct lws *</i> <b>wsi</b>)
<h3>Arguments</h3>
<dl>
<dt><b>wsi</b>
<dd>Websocket connection instance to get callback for
</dl>
<hr>
<h2>lws_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>
<i>int</i>
<b>lws_callback_on_writable_all_protocol</b>
(<i>const struct lws_context *</i> <b>context</b>,
<i>const struct lws_protocols *</i> <b>protocol</b>)
<h3>Arguments</h3>
<dl>
<dt><b>context</b>
<dd>lws_context
<dt><b>protocol</b>
<dd>Protocol whose connections will get callbacks
</dl>
<hr>
<h2>lws_http_transaction_completed - wait for new http transaction or close</h2>
<i>int LWS_WARN_UNUSED_RESULT</i>
<b>lws_http_transaction_completed</b>
(<i>struct lws *</i> <b>wsi</b>)
<h3>Arguments</h3>
<dl>
<dt><b>wsi</b>
<dd>websocket connection
</dl>
<h3>Description</h3>
<blockquote>
Returns 1 if the HTTP connection must close now
Returns 0 and resets connection to wait for new HTTP header /
transaction if possible
</blockquote>
<hr>
<h2>lws_adopt_socket - adopt foreign socket as if listen socket accepted it</h2>
<i>struct lws *</i>
<b>lws_adopt_socket</b>
(<i>struct lws_context *</i> <b>context</b>,
<i>lws_sockfd_type</i> <b>accept_fd</b>)
<h3>Arguments</h3>
<dl>
<dt><b>context</b>
<dd>lws context
<dt><b>accept_fd</b>
<dd>fd of already-accepted socket to adopt
</dl>
<h3>Description</h3>
<blockquote>
Either returns new wsi bound to accept_fd, or closes accept_fd and
returns NULL, having cleaned up any new wsi pieces.
<p>
LWS adopts the socket in http serving mode, it's ready to accept an upgrade
to ws or just serve http.
</blockquote>
<hr>
<h2>lws_adopt_socket_readbuf - adopt foreign socket and first rx as if listen socket accepted it</h2>
<i>LWS_EXTERN struct lws *</i>
<b>lws_adopt_socket_readbuf</b>
(<i>struct lws_context *</i> <b>context</b>,
<i>lws_sockfd_type</i> <b>accept_fd</b>,
<i>const char *</i> <b>readbuf</b>,
<i>size_t</i> <b>len</b>)
<h3>Arguments</h3>
<dl>
<dt><b>context</b>
<dd>lws context
<dt><b>accept_fd</b>
<dd>fd of already-accepted socket to adopt
<dt><b>readbuf</b>
<dd>NULL or pointer to data that must be drained before reading from
accept_fd
<dt><b>len</b>
<dd>The length of the data held at <tt><b>readbuf</b></tt>
</dl>
<h3>Description</h3>
<blockquote>
Either returns new wsi bound to accept_fd, or closes accept_fd and
returns NULL, having cleaned up any new wsi pieces.
<p>
LWS adopts the socket in http serving mode, it's ready to accept an upgrade
to ws or just serve http.
<p>
If your external code did not already read from the socket, you can use
<b>lws_adopt_socket</b> instead.
<p>
This api is guaranteed to use the data at <tt><b>readbuf</b></tt> first, before reading from
the socket.
<p>
<tt><b>readbuf</b></tt> is limited to the size of the ah rx buf, currently 2048 bytes.
</blockquote>
<hr>
<h2>lws_serve_http_file - Send a file back to the client using http</h2>
<i>int</i>
<b>lws_serve_http_file</b>
(<i>struct lws *</i> <b>wsi</b>,
<i>const char *</i> <b>file</b>,
<i>const char *</i> <b>content_type</b>,
<i>const char *</i> <b>other_headers</b>,
<i>int</i> <b>other_headers_len</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
<dt><b>other_headers</b>
<dd>NULL or pointer to header string
<dt><b>other_headers_len</b>
<dd>length of the other headers if non-NULL
</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.
<p>
Returning &lt;0 indicates error and the wsi should be closed.  Returning
&gt;0 indicates the file was completely sent and
<b>lws_http_transaction_completed</b> called on the wsi (and close if != 0)
==0 indicates the file transfer is started and needs more service later,
the wsi should be left alone.
</blockquote>
<hr>
<h2>lws_service_fd_tsi - Service polled socket with something waiting</h2>
<i>int</i>
<b>lws_service_fd_tsi</b>
(<i>struct lws_context *</i> <b>context</b>,
<i>struct lws_pollfd *</i> <b>pollfd</b>,
<i>int</i> <b>tsi</b>)
<h3>Arguments</h3>
<dl>
<dt><b>context</b>
<dd>Websocket context
<dt><b>pollfd</b>
<dd>The pollfd entry describing the socket fd and which events
happened.
</dl>
<h3>Description</h3>
<blockquote>
This function takes a pollfd that has POLLIN or POLLOUT activity and
services it according to the state of the associated
struct lws.
<p>
The one call deals with all "service" that might happen on a socket
including listen accepts, http files as well as websocket protocol.
<p>
If a pollfd says it has something, you can just pass it to
<b>lws_service_fd</b> whether it is a socket handled by lws or not.
If it sees it is a lws socket, the traffic will be handled and
pollfd-&gt;revents will be zeroed now.
<p>
If the socket is foreign to lws, it leaves revents alone.  So you can
see if you should service yourself by checking the pollfd revents
after letting lws try to service it.
</blockquote>
<hr>
<h2>lws_service - Service any pending websocket activity</h2>
<i>int</i>
<b>lws_service</b>
(<i>struct lws_context *</i> <b>context</b>,
<i>int</i> <b>timeout_ms</b>)
<h3>Arguments</h3>
<dl>
<dt><b>context</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) 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>struct lws_plat_file_ops - Platform-specific file operations</h2>
<b>struct lws_plat_file_ops</b> {<br>
&nbsp; &nbsp; <i>lws_filefd_type (*</i><b>open</b>) <i>(struct lws *wsi, const char *filename,unsigned long *filelen, int flags)</i>;<br>
&nbsp; &nbsp; <i>int (*</i><b>close</b>) <i>(struct lws *wsi, lws_filefd_type fd)</i>;<br>
&nbsp; &nbsp; <i>unsigned long (*</i><b>seek_cur</b>) <i>(struct lws *wsi, lws_filefd_type fd,long offset_from_cur_pos)</i>;<br>
&nbsp; &nbsp; <i>int (*</i><b>read</b>) <i>(struct lws *wsi, lws_filefd_type fd, unsigned long *amount,unsigned char *buf, unsigned long len)</i>;<br>
&nbsp; &nbsp; <i>int (*</i><b>write</b>) <i>(struct lws *wsi, lws_filefd_type fd, unsigned long *amount,unsigned char *buf, unsigned long len)</i>;<br>
};<br>
<h3>Members</h3>
<dl>
<dt><b>open</b>
<dd>Open file (always binary access if plat supports it)
filelen is filled on exit to be the length of the file
flags should be set to O_RDONLY or O_RDWR
<dt><b>close</b>
<dd>Close file
<dt><b>seek_cur</b>
<dd>Seek from current position
<dt><b>read</b>
<dd>Read fron file *amount is set on exit to amount read
<dt><b>write</b>
<dd>Write to file *amount is set on exit as amount written
</dl>
<h3>Description</h3>
<blockquote>
<p>
These provide platform-agnostic ways to deal with filesystem access in the
library and in the user code.
</blockquote>
<hr>
<h2>lws_callback_function - User server actions</h2>
<i>typedef int</i>
<b>lws_callback_function</b>
(<i>struct lws *</i> <b>wsi</b>,
<i>enum lws_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 lws_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 the server completes a handshake with
an incoming client.  If you built the library
with ssl support, <tt><b>in</b></tt> is a pointer to the
ssl struct associated with the connection or
NULL.
</blockquote>
<h3>LWS_CALLBACK_CLIENT_CONNECTION_ERROR</h3>
<blockquote>
the request client connection has
been unable to complete a handshake with the remote server.  If
in is non-NULL, you can find an error string of length len where
it points to.
</blockquote>
<h3>LWS_CALLBACK_CLIENT_FILTER_PRE_ESTABLISH</h3>
<blockquote>
this is the last chance for the
client user code to examine the http headers
and decide to reject the connection.  If the
content in the headers is interesting to the
client (url, etc) it needs to copy it out at
this point since it will be destroyed before
the CLIENT_ESTABLISHED call
</blockquote>
<h3>LWS_CALLBACK_CLIENT_ESTABLISHED</h3>
<blockquote>
after your client connection completed
a handshake with the remote server
</blockquote>
<h3>LWS_CALLBACK_CLOSED</h3>
<blockquote>
when the websocket session ends
</blockquote>
<h3>LWS_CALLBACK_CLOSED_HTTP</h3>
<blockquote>
when a HTTP (non-websocket) session ends
</blockquote>
<h3>LWS_CALLBACK_RECEIVE</h3>
<blockquote>
data has appeared for this server endpoint from a
remote client, it can be found at *in and is
len bytes long
</blockquote>
<h3>LWS_CALLBACK_CLIENT_RECEIVE_PONG</h3>
<blockquote>
if you elected to see PONG packets,
they appear with this callback reason.  PONG
packets only exist in 04+ protocol
</blockquote>
<h3>LWS_CALLBACK_CLIENT_RECEIVE</h3>
<blockquote>
data has appeared from the server for the
client connection, 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>lws_serve_http_file</b> makes it very
simple to send back a file to the client.
Normally after sending the file you are done
with the http connection, since the rest of the
activity will come by websockets from the script
that was delivered by http, so you will want to
return 1; to close and free up the connection.
That's important because it uses a slot in the
total number of client connections allowed set
by MAX_CLIENTS.
</blockquote>
<h3>LWS_CALLBACK_HTTP_BODY</h3>
<blockquote>
the next <tt><b>len</b></tt> bytes data from the http
request body HTTP connection is now available in <tt><b>in</b></tt>.
</blockquote>
<h3>LWS_CALLBACK_HTTP_BODY_COMPLETION</h3>
<blockquote>
the expected amount of http request
body has been delivered
</blockquote>
<h3>LWS_CALLBACK_HTTP_WRITEABLE</h3>
<blockquote>
you can write more down the http protocol
link now.
</blockquote>
<h3>LWS_CALLBACK_HTTP_FILE_COMPLETION</h3>
<blockquote>
a file requested to be send down
http link has completed.
</blockquote>
<h3>LWS_CALLBACK_SERVER_WRITEABLE</h3>
<blockquote>
If you call
<b>lws_callback_on_writable</b> on a connection, you will
get one of these callbacks coming when the connection socket
is able to accept another write packet without blocking.
If it already was able to take another packet without blocking,
you'll get this callback at the next call to the service loop
function.  Notice that CLIENTs get LWS_CALLBACK_CLIENT_WRITEABLE
and servers get LWS_CALLBACK_SERVER_WRITEABLE.
</blockquote>
<h3>LWS_CALLBACK_FILTER_NETWORK_CONNECTION</h3>
<blockquote>
called when a client connects to
the server at network level; the connection is accepted but then
passed to this callback to decide whether to hang up immediately
or not, based on the client IP.  <tt><b>in</b></tt> contains the connection
socket's descriptor. Since the client connection information is
not available yet, <tt><b>wsi</b></tt> still pointing to the main server socket.
Return non-zero to terminate the connection before sending or
receiving anything. Because this happens immediately after the
network connection from the client, there's no websocket protocol
selected yet so this callback is issued only to protocol 0.
</blockquote>
<h3>LWS_CALLBACK_SERVER_NEW_CLIENT_INSTANTIATED</h3>
<blockquote>
A new client just had
been connected, accepted, and instantiated into the pool. This
callback allows setting any relevant property to it. Because this
happens immediately after the instantiation of a new client,
there's no websocket protocol selected yet so this callback is
issued only to protocol 0. Only <tt><b>wsi</b></tt> is defined, pointing to the
new client, and the return value is ignored.
</blockquote>
<h3>LWS_CALLBACK_FILTER_HTTP_CONNECTION</h3>
<blockquote>
called when the request has
been received and parsed from the client, but the response is
not sent yet.  Return non-zero to disallow the connection.
<tt><b>user</b></tt> is a pointer to the connection user space allocation,
<tt><b>in</b></tt> is the URI, eg, "/"
In your handler you can use the public APIs
<b>lws_hdr_total_length</b> / <b>lws_hdr_copy</b> to access all of the
headers using the header enums lws_token_indexes from
libwebsockets.h to check for and read the supported header
presence and content before deciding to allow the http
connection to proceed or to kill the connection.
</blockquote>
<h3>LWS_CALLBACK_FILTER_PROTOCOL_CONNECTION</h3>
<blockquote>
called when the handshake has
been received and parsed from the client, but the response is
not sent yet.  Return non-zero to disallow the connection.
<tt><b>user</b></tt> is a pointer to the connection user space allocation,
<tt><b>in</b></tt> is the requested protocol name
In your handler you can use the public APIs
<b>lws_hdr_total_length</b> / <b>lws_hdr_copy</b> to access all of the
headers using the header enums lws_token_indexes from
libwebsockets.h to check for and read the supported header
presence and content before deciding to allow the handshake
to proceed or to kill the connection.
</blockquote>
<h3>LWS_CALLBACK_OPENSSL_LOAD_EXTRA_CLIENT_VERIFY_CERTS</h3>
<blockquote>
if configured for
including OpenSSL support, this callback allows your user code
to perform extra <b>SSL_CTX_load_verify_locations</b> or similar
calls to direct OpenSSL where to find certificates the client
can use to confirm the remote server identity.  <tt><b>user</b></tt> is the
OpenSSL SSL_CTX*
</blockquote>
<h3>LWS_CALLBACK_OPENSSL_LOAD_EXTRA_SERVER_VERIFY_CERTS</h3>
<blockquote>
if configured for
including OpenSSL support, this callback allows your user code
to load extra certifcates into the server which allow it to
verify the validity of certificates returned by clients.  <tt><b>user</b></tt>
is the server's OpenSSL SSL_CTX*
</blockquote>
<h3>LWS_CALLBACK_OPENSSL_CONTEXT_REQUIRES_PRIVATE_KEY</h3>
<blockquote>
if configured for
including OpenSSL support but no private key file has been
specified (ssl_private_key_filepath is NULL), this is called to
allow the user to set the private key directly via libopenssl
and perform further operations if required; this might be useful
in situations where the private key is not directly accessible
by the OS, for example if it is stored on a smartcard
<tt><b>user</b></tt> is the server's OpenSSL SSL_CTX*
</blockquote>
<h3>LWS_CALLBACK_OPENSSL_PERFORM_CLIENT_CERT_VERIFICATION</h3>
<blockquote>
if the
libwebsockets context was created with the option
LWS_SERVER_OPTION_REQUIRE_VALID_OPENSSL_CLIENT_CERT, then this
callback is generated during OpenSSL verification of the cert
sent from the client.  It is sent to protocol[0] callback as
no protocol has been negotiated on the connection yet.
Notice that the libwebsockets context and wsi are both NULL
during this callback.  See
</blockquote>
<h3>http</h3>
<blockquote>
//www.openssl.org/docs/ssl/SSL_CTX_set_verify.html
to understand more detail about the OpenSSL callback that
generates this libwebsockets callback and the meanings of the
arguments passed.  In this callback, <tt><b>user</b></tt> is the x509_ctx,
<tt><b>in</b></tt> is the ssl pointer and <tt><b>len</b></tt> is preverify_ok
Notice that this callback maintains libwebsocket return
conventions, return 0 to mean the cert is OK or 1 to fail it.
This also means that if you don't handle this callback then
the default callback action of returning 0 allows the client
certificates.
</blockquote>
<h3>LWS_CALLBACK_CLIENT_APPEND_HANDSHAKE_HEADER</h3>
<blockquote>
this callback happens
when a client handshake is being compiled.  <tt><b>user</b></tt> is NULL,
<tt><b>in</b></tt> is a char **, it's pointing to a char * which holds the
next location in the header buffer where you can add
headers, and <tt><b>len</b></tt> is the remaining space in the header buffer,
which is typically some hundreds of bytes.  So, to add a canned
cookie, your handler code might look similar to:
<p>
char **p = (char **)in;
<p>
if (len &lt; 100)
return 1;
<p>
*p += sprintf(*p, "Cookie: a=b\x0d\x0a");
<p>
return 0;
<p>
Notice if you add anything, you just have to take care about
the CRLF on the line you added.  Obviously this callback is
optional, if you don't handle it everything is fine.
<p>
Notice the callback is coming to protocols[0] all the time,
because there is no specific protocol handshook yet.
</blockquote>
<h3>LWS_CALLBACK_CONFIRM_EXTENSION_OKAY</h3>
<blockquote>
When the server handshake code
sees that it does support a requested extension, before
accepting the extension by additing to the list sent back to
the client it gives this callback just to check that it's okay
to use that extension.  It calls back to the requested protocol
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
valid.  Note though at this time the ESTABLISHED callback hasn't
happened yet so if you initialize <tt><b>user</b></tt> content there, <tt><b>user</b></tt>
content during this callback might not be useful for anything.
Notice this callback comes to protocols[0].
</blockquote>
<h3>LWS_CALLBACK_CLIENT_CONFIRM_EXTENSION_SUPPORTED</h3>
<blockquote>
When a client
connection is being prepared to start a handshake to a server,
each supported extension is checked with protocols[0] callback
with this reason, giving the user code a chance to suppress the
claim to support that extension by returning non-zero.  If
unhandled, by default 0 will be returned and the extension
support included in the header to the server.  Notice this
callback comes to protocols[0].
</blockquote>
<h3>LWS_CALLBACK_PROTOCOL_INIT</h3>
<blockquote>
One-time call per protocol so it can
do initial setup / allocations etc
</blockquote>
<h3>LWS_CALLBACK_PROTOCOL_DESTROY</h3>
<blockquote>
One-time call per protocol indicating
this protocol won't get used at all after this callback, the
context is getting destroyed.  Take the opportunity to
deallocate everything that was allocated by the protocol.
</blockquote>
<h3>LWS_CALLBACK_WSI_CREATE</h3>
<blockquote>
outermost (earliest) wsi create notification
</blockquote>
<h3>LWS_CALLBACK_WSI_DESTROY</h3>
<blockquote>
outermost (latest) wsi destroy notification
<p>
The next five reasons are optional and only need taking care of if you
will be integrating libwebsockets sockets into an external polling
array.
<p>
For these calls, <tt><b>in</b></tt> points to a struct lws_pollargs that
contains <tt><b>fd</b></tt>, <tt><b>events</b></tt> and <tt><b>prev_events</b></tt> members
</blockquote>
<h3>LWS_CALLBACK_ADD_POLL_FD</h3>
<blockquote>
libwebsocket deals with its <b>poll</b> loop
internally, but in the case you are integrating with another
server you will need to have libwebsocket sockets share a
polling array with the other server.  This and the other
POLL_FD related callbacks let you put your specialized
poll array interface code in the callback for protocol 0, the
first protocol you support, usually the HTTP protocol in the
serving case.
This callback happens when a socket needs to be
</blockquote>
<h3>added to the polling loop</h3>
<blockquote>
<tt><b>in</b></tt> points to a struct
lws_pollargs; the <tt><b>fd</b></tt> member of the struct is the file
descriptor, and <tt><b>events</b></tt> contains the active events.
<p>
If you are using the internal polling loop (the "service"
callback), you can just ignore these callbacks.
</blockquote>
<h3>LWS_CALLBACK_DEL_POLL_FD</h3>
<blockquote>
This callback happens when a socket descriptor
needs to be removed from an external polling array.  <tt><b>in</b></tt> is
again the struct lws_pollargs containing the <tt><b>fd</b></tt> member
to be removed.  If you are using the internal polling
loop, you can just ignore it.
</blockquote>
<h3>LWS_CALLBACK_CHANGE_MODE_POLL_FD</h3>
<blockquote>
This callback happens when
libwebsockets wants to modify the events for a connectiion.
<tt><b>in</b></tt> is the struct lws_pollargs with the <tt><b>fd</b></tt> to change.
The new event mask is in <tt><b>events</b></tt> member and the old mask is in
the <tt><b>prev_events</b></tt> member.
If you are using the internal polling loop, you can just ignore
it.
</blockquote>
<h3>LWS_CALLBACK_UNLOCK_POLL</h3>
<blockquote>
These allow the external poll changes driven
by libwebsockets to participate in an external thread locking
scheme around the changes, so the whole thing is threadsafe.
These are called around three activities in the library,
- inserting a new wsi in the wsi / fd table (len=1)
- deleting a wsi from the wsi / fd table (len=1)
- changing a wsi's POLLIN/OUT state (len=0)
Locking and unlocking external synchronization objects when
len == 1 allows external threads to be synchronized against
wsi lifecycle changes if it acquires the same lock for the
duration of wsi dereference from the other thread context.
</blockquote>
<h3>LWS_CALLBACK_WS_PEER_INITIATED_CLOSE</h3>
<blockquote>
The peer has sent an unsolicited Close WS packet.  <tt><b>in</b></tt> and
<tt><b>len</b></tt> are the optional close code (first 2 bytes, network
order) and the optional additional information which is not
defined in the standard, and may be a string or non-human-
readble data.
If you return 0 lws will echo the close and then close the
connection.  If you return nonzero lws will just close the
connection.
</blockquote>
<hr>
<h2>lws_extension_callback_function - Hooks to allow extensions to operate</h2>
<i>typedef int</i>
<b>lws_extension_callback_function</b>
(<i>struct lws_context *</i> <b>context</b>,
<i>const struct lws_extension *</i> <b>ext</b>,
<i>struct lws *</i> <b>wsi</b>,
<i>enum lws_extension_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>context</b>
<dd>Websockets context
<dt><b>ext</b>
<dd>This extension
<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 ptr 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>
Each extension that is active on a particular connection receives
callbacks during the connection lifetime to allow the extension to
operate on websocket data and manage itself.
<p>
Libwebsockets takes care of allocating and freeing "user" memory for
each active extension on each connection.  That is what is pointed to
by the <tt><b>user</b></tt> parameter.
</blockquote>
<h3>LWS_EXT_CB_CONSTRUCT</h3>
<blockquote>
called when the server has decided to
select this extension from the list provided by the client,
just before the server will send back the handshake accepting
the connection with this extension active.  This gives the
extension a chance to initialize its connection context found
in <tt><b>user</b></tt>.
</blockquote>
<h3>LWS_EXT_CB_CLIENT_CONSTRUCT</h3>
<blockquote>
same as LWS_EXT_CB_CONSTRUCT
but called when client is instantiating this extension.  Some
extensions will work the same on client and server side and then
you can just merge handlers for both CONSTRUCTS.
</blockquote>
<h3>LWS_EXT_CB_DESTROY</h3>
<blockquote>
called when the connection the extension was
being used on is about to be closed and deallocated.  It's the
last chance for the extension to deallocate anything it has
allocated in the user data (pointed to by <tt><b>user</b></tt>) before the
user data is deleted.  This same callback is used whether you
are in client or server instantiation context.
</blockquote>
<h3>LWS_EXT_CB_PACKET_RX_PREPARSE</h3>
<blockquote>
when this extension was active on
a connection, and a packet of data arrived at the connection,
it is passed to this callback to give the extension a chance to
change the data, eg, decompress it.  <tt><b>user</b></tt> is pointing to the
extension's private connection context data, <tt><b>in</b></tt> is pointing
to an lws_tokens struct, it consists of a char * pointer called
token, and an int called token_len.  At entry, these are
set to point to the received buffer and set to the content
length.  If the extension will grow the content, it should use
a new buffer allocated in its private user context data and
set the pointed-to lws_tokens members to point to its buffer.
</blockquote>
<h3>LWS_EXT_CB_PACKET_TX_PRESEND</h3>
<blockquote>
this works the same way as
LWS_EXT_CB_PACKET_RX_PREPARSE above, except it gives the
extension a chance to change websocket data just before it will
be sent out.  Using the same lws_token pointer scheme in <tt><b>in</b></tt>,
the extension can change the buffer and the length to be
transmitted how it likes.  Again if it wants to grow the
buffer safely, it should copy the data into its own buffer and
set the lws_tokens token pointer to it.
</blockquote>
<hr>
<h2>struct lws_protocols - List of protocols and handlers server supports.</h2>
<b>struct lws_protocols</b> {<br>
&nbsp; &nbsp; <i>const char *</i> <b>name</b>;<br>
&nbsp; &nbsp; <i>lws_callback_function *</i> <b>callback</b>;<br>
&nbsp; &nbsp; <i>size_t</i> <b>per_session_data_size</b>;<br>
&nbsp; &nbsp; <i>size_t</i> <b>rx_buffer_size</b>;<br>
&nbsp; &nbsp; <i>unsigned int</i> <b>id</b>;<br>
&nbsp; &nbsp; <i>void *</i> <b>user</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>rx_buffer_size</b>
<dd>if you want atomic frames delivered to the callback, you
should set this to the size of the biggest legal frame that
you support.  If the frame size is exceeded, there is no
error, but the buffer will spill to the user callback when
full, which you can detect by using
<b>lws_remaining_packet_payload</b>.  Notice that you
just talk about frame size here, the LWS_PRE
and post-padding are automatically also allocated on top.
<dt><b>id</b>
<dd>ignored by lws, but useful to contain user information bound
to the selected protocol.  For example if this protocol was
called "myprotocol-v2", you might set id to 2, and the user
code that acts differently according to the version can do so by
switch (wsi-&gt;protocol-&gt;id), user code might use some bits as
capability flags based on selected protocol version, etc.
<dt><b>user</b>
<dd>User provided context data at the protocol level.
Accessible via lws_get_protocol(wsi)-&gt;user
This should not be confused with wsi-&gt;user, it is not the same.
The library completely ignores any value in here.
</dl>
<h3>Description</h3>
<blockquote>
This structure represents one protocol supported by the server.  An
array of these structures is passed to <b>lws_create_server</b>
allows as many protocols as you like to be handled by one server.
<p>
The first protocol given has its callback used for user callbacks when
there is no agreed protocol name, that's true during HTTP part of the
</blockquote>
<h3>connection and true if the client did not send a Protocol</h3>
<blockquote>
header.
</blockquote>
<hr>
<h2>struct lws_ext_options - Option arguments to the extension.  These are used in the negotiation at ws upgrade time. The helper function lws_ext_parse_options() uses these to generate callbacks</h2>
<b>struct lws_ext_options</b> {<br>
&nbsp; &nbsp; <i>const char *</i> <b>name</b>;<br>
&nbsp; &nbsp; <i>enum lws_ext_options_types</i> <b>type</b>;<br>
};<br>
<h3>Members</h3>
<dl>
<dt><b>name</b>
<dd>Option name, eg, "server_no_context_takeover"
<dt><b>type</b>
<dd>What kind of args the option can take
</dl>
<hr>
<h2>struct lws_extension - An extension we know how to cope with</h2>
<b>struct lws_extension</b> {<br>
&nbsp; &nbsp; <i>const char *</i> <b>name</b>;<br>
&nbsp; &nbsp; <i>lws_extension_callback_function *</i> <b>callback</b>;<br>
&nbsp; &nbsp; <i>const char *</i> <b>client_offer</b>;<br>
};<br>
<h3>Members</h3>
<dl>
<dt><b>name</b>
<dd>Formal extension name, eg, "permessage-deflate"
<dt><b>callback</b>
<dd>Service callback
<dt><b>client_offer</b>
<dd>String containing exts and options client offers
</dl>
<hr>
<h2>struct lws_context_creation_info - parameters to create context with</h2>
<b>struct lws_context_creation_info</b> {<br>
&nbsp; &nbsp; <i>int</i> <b>port</b>;<br>
&nbsp; &nbsp; <i>const char *</i> <b>iface</b>;<br>
&nbsp; &nbsp; <i>const struct lws_protocols *</i> <b>protocols</b>;<br>
&nbsp; &nbsp; <i>const struct lws_extension *</i> <b>extensions</b>;<br>
&nbsp; &nbsp; <i>const struct lws_token_limits *</i> <b>token_limits</b>;<br>
&nbsp; &nbsp; <i>const char *</i> <b>ssl_cert_filepath</b>;<br>
&nbsp; &nbsp; <i>const char *</i> <b>ssl_private_key_filepath</b>;<br>
&nbsp; &nbsp; <i>const char *</i> <b>ssl_ca_filepath</b>;<br>
&nbsp; &nbsp; <i>const char *</i> <b>ssl_cipher_list</b>;<br>
&nbsp; &nbsp; <i>const char *</i> <b>http_proxy_address</b>;<br>
&nbsp; &nbsp; <i>unsigned int</i> <b>http_proxy_port</b>;<br>
&nbsp; &nbsp; <i>int</i> <b>gid</b>;<br>
&nbsp; &nbsp; <i>int</i> <b>uid</b>;<br>
&nbsp; &nbsp; <i>unsigned int</i> <b>options</b>;<br>
&nbsp; &nbsp; <i>void *</i> <b>user</b>;<br>
&nbsp; &nbsp; <i>int</i> <b>ka_time</b>;<br>
&nbsp; &nbsp; <i>int</i> <b>ka_probes</b>;<br>
&nbsp; &nbsp; <i>int</i> <b>ka_interval</b>;<br>
#ifdef LWS_OPENSSL_SUPPORT<br>
&nbsp; &nbsp; <i>void *</i> <b>provided_client_ssl_ctx</b>;<br>
#else<br>
&nbsp; &nbsp; <i>void *</i> <b>provided_client_ssl_ctx</b>;<br>
#endif<br>
&nbsp; &nbsp; <i>short</i> <b>max_http_header_data</b>;<br>
&nbsp; &nbsp; <i>short</i> <b>max_http_header_pool</b>;<br>
&nbsp; &nbsp; <i>unsigned int</i> <b>count_threads</b>;<br>
&nbsp; &nbsp; <i>unsigned int</i> <b>fd_limit_per_thread</b>;<br>
&nbsp; &nbsp; <i>unsigned int</i> <b>timeout_secs</b>;<br>
&nbsp; &nbsp; <i>const char *</i> <b>ecdh_curve</b>;<br>
};<br>
<h3>Members</h3>
<dl>
<dt><b>port</b>
<dd>Port to listen on... you can use CONTEXT_PORT_NO_LISTEN 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>iface</b>
<dd>NULL to bind the listen socket to all interfaces, or the
interface name, eg, "eth2"
<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>extensions</b>
<dd>NULL or array of lws_extension structs listing the
extensions this context supports.  If you configured with
--without-extensions, you should give NULL here.
<dt><b>token_limits</b>
<dd>NULL or struct lws_token_limits pointer which is initialized
with a token length limit for each possible WSI_TOKEN_***
<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;
if this is set to NULL but sll_cert_filepath is set, the
OPENSSL_CONTEXT_REQUIRES_PRIVATE_KEY callback is called
to allow setting of the private key directly via openSSL
library calls
<dt><b>ssl_ca_filepath</b>
<dd>CA certificate filepath or NULL
<dt><b>ssl_cipher_list</b>
<dd>List of valid ciphers to use (eg,
"RC4-MD5:RC4-SHA:AES128-SHA:AES256-SHA:HIGH:!DSS:!aNULL"
or you can leave it as NULL to get "DEFAULT"
<dt><b>http_proxy_address</b>
<dd>If non-NULL, attempts to proxy via the given address.
If proxy auth is required, use format
"username:password<tt><b>server</b></tt>:port"
<dt><b>http_proxy_port</b>
<dd>If http_proxy_address was non-NULL, uses this port at
the address
<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.
<dt><b>options</b>
<dd>0, or LWS_SERVER_OPTION_... bitfields
<dt><b>user</b>
<dd>optional user pointer that can be recovered via the context
pointer using lws_context_user
<dt><b>ka_time</b>
<dd>0 for no keepalive, otherwise apply this keepalive timeout to
all libwebsocket sockets, client or server
<dt><b>ka_probes</b>
<dd>if ka_time was nonzero, after the timeout expires how many
times to try to get a response from the peer before giving up
and killing the connection
<dt><b>ka_interval</b>
<dd>if ka_time was nonzero, how long to wait before each ka_probes
attempt
<dt><b>provided_client_ssl_ctx</b>
<dd>If non-null, swap out libwebsockets ssl
implementation for the one provided by provided_ssl_ctx.
Libwebsockets no longer is responsible for freeing the context
if this option is selected.
<dt><b>provided_client_ssl_ctx</b>
<dd>If non-null, swap out libwebsockets ssl
implementation for the one provided by provided_ssl_ctx.
Libwebsockets no longer is responsible for freeing the context
if this option is selected.
<dt><b>max_http_header_data</b>
<dd>The max amount of header payload that can be handled
in an http request (unrecognized header payload is dropped)
<dt><b>max_http_header_pool</b>
<dd>The max number of connections with http headers that
can be processed simultaneously (the corresponding memory is
allocated for the lifetime of the context).  If the pool is
busy new incoming connections must wait for accept until one
becomes free.
<dt><b>count_threads</b>
<dd>how many contexts to create in an array, 0 = 1
<dt><b>fd_limit_per_thread</b>
<dd>nonzero means restrict each service thread to this
many fds, 0 means the default which is divide the process fd
limit by the number of threads.
<dt><b>timeout_secs</b>
<dd>various processes involving network roundtrips in the
library are protected from hanging forever by timeouts.  If
nonzero, this member lets you set the timeout used in seconds.
Otherwise a default timeout is used.
<dt><b>ecdh_curve</b>
<dd>if NULL, defaults to initializing server with "prime256v1"
</dl>
<hr>
<h2>struct lws_client_connect_info - parameters to connect with when using lws_client_connect_via_info()</h2>
<b>struct lws_client_connect_info</b> {<br>
&nbsp; &nbsp; <i>struct lws_context *</i> <b>context</b>;<br>
&nbsp; &nbsp; <i>const char *</i> <b>address</b>;<br>
&nbsp; &nbsp; <i>int</i> <b>port</b>;<br>
&nbsp; &nbsp; <i>int</i> <b>ssl_connection</b>;<br>
&nbsp; &nbsp; <i>const char *</i> <b>path</b>;<br>
&nbsp; &nbsp; <i>const char *</i> <b>host</b>;<br>
&nbsp; &nbsp; <i>const char *</i> <b>origin</b>;<br>
&nbsp; &nbsp; <i>const char *</i> <b>protocol</b>;<br>
&nbsp; &nbsp; <i>int</i> <b>ietf_version_or_minus_one</b>;<br>
&nbsp; &nbsp; <i>void *</i> <b>userdata</b>;<br>
&nbsp; &nbsp; <i>const struct lws_extension *</i> <b>client_exts</b>;<br>
&nbsp; &nbsp; <i>const char *</i> <b>method</b>;<br>
};<br>
<h3>Members</h3>
<dl>
<dt><b>context</b>
<dd>lws context to create connection in
<dt><b>address</b>
<dd>remote address to connect to
<dt><b>port</b>
<dd>remote port to connect to
<dt><b>ssl_connection</b>
<dd>nonzero for ssl
<dt><b>path</b>
<dd>uri path
<dt><b>host</b>
<dd>content of host header
<dt><b>origin</b>
<dd>content of origin header
<dt><b>protocol</b>
<dd>list of ws protocols
<dt><b>ietf_version_or_minus_one</b>
<dd>currently leave at 0 or -1
<dt><b>userdata</b>
<dd>if non-NULL, use this as wsi user_data instead of malloc it
<dt><b>client_exts</b>
<dd>array of extensions that may be used on connection
<dt><b>method</b>
<dd>if non-NULL, do this http method instead of ws[s] upgrade.
use "GET" to be a simple http client connection
</dl>
<hr>
<h2>lws_close_reason - Set reason and aux data to send with Close packet If you are going to return nonzero from the callback requesting the connection to close, you can optionally call this to set the reason the peer will be told if possible.</h2>
<i>LWS_EXTERN void</i>
<b>lws_close_reason</b>
(<i>struct lws *</i> <b>wsi</b>,
<i>enum lws_close_status</i> <b>status</b>,
<i>unsigned char *</i> <b>buf</b>,
<i>size_t</i> <b>len</b>)
<h3>Arguments</h3>
<dl>
<dt><b>wsi</b>
<dd>The websocket connection to set the close reason on
<dt><b>status</b>
<dd>A valid close status from websocket standard
<dt><b>buf</b>
<dd>NULL or buffer containing up to 124 bytes of auxiliary data
<dt><b>len</b>
<dd>Length of data in <tt><b>buf</b></tt> to send
</dl>
<hr>