lws_frame_is_binary -

Arguments

wsi

the connection we are inquiring about

Description

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.

libwebsockets_remaining_packet_payload - Bytes to come before "overall" rx packet is complete

Arguments

wsi

Websocket instance (available from user callback)

Description

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 libwebsockets_remaining_packet_payload will return 0.

Many protocols won't care becuse their packets are always small.

lws_get_library_version -

Arguments

void

no arguments

Description

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

libwebsockets_get_peer_addresses - Get client address information

Arguments

context

Libwebsockets context

wsi

Local struct libwebsocket associated with

fd

Connection socket descriptor

name

Buffer to take client address name

name_len

Length of client address name buffer

rip

Buffer to take client address IP qotted quad

rip_len

Length of client address IP buffer

Description

This function fills in name and rip with the name and IP of the client connected with socket descriptor fd. Names may be truncated if there is not enough room. If either cannot be determined, they will be returned as valid zero-length strings.

libwebsocket_service_fd - Service polled socket with something waiting

Arguments

context

Websocket context

pollfd

The pollfd entry describing the socket fd and which events happened.

Description

This function takes a pollfd that has POLLIN or POLLOUT activity and services it according to the state of the associated struct libwebsocket.

The one call deals with all "service" that might happen on a socket including listen accepts, http files as well as websocket protocol.

If a pollfd says it has something, you can just pass it to libwebsocket_serice_fd 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->revents will be zeroed now.

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.

libwebsocket_context_destroy - Destroy the websocket context

Arguments

context

Websocket context

Description

This function closes any active connections and then frees the context. After calling this, any further use of the context is undefined.

libwebsocket_context_user - get the user data associated with the context

Arguments

context

Websocket context

Description

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.

libwebsocket_service - Service any pending websocket activity

Arguments

context

Websocket context

timeout_ms

Timeout for poll; 0 means return immediately if nothing needed service otherwise block and service immediately, returning after the timeout if nothing needed service.

Description

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.

1) Accept new connections to our context's server

2) Call the receive callback for incoming frame data received by server or client connections.

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.

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.

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.

libwebsocket_callback_on_writable - Request a callback when this socket becomes able to be written to without blocking

Arguments

context

libwebsockets context

wsi

Websocket connection instance to get callback for

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.

Arguments

protocol

Protocol whose connections will get callbacks

libwebsocket_set_timeout - marks the wsi as subject to a timeout

Arguments

wsi

Websocket connection instance

reason

timeout reason

secs

how many seconds

Description

You will not need this unless you are doing something special

libwebsocket_get_socket_fd - returns the socket file descriptor

Arguments

wsi

Websocket connection instance

Description

You will not need this unless you are doing something special

libwebsocket_rx_flow_control - Enable and disable socket servicing for receieved packets.

Arguments

wsi

Websocket connection instance to get callback for

enable

0 = disable read servicing for this connection, 1 = enable

Description

If the output side of a server process becomes choked, this allows flow control for the input side.

libwebsocket_rx_flow_allow_all_protocol - Allow all connections with this protocol to receive

Arguments

protocol

all connections using this protocol will be allowed to receive

Description

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.

libwebsocket_canonical_hostname - returns this host's hostname

Arguments

context

Websocket context

Description

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.

libwebsocket_create_context - Create the websocket handler

Arguments

info

pointer to struct with parameters

Description

This function creates the listening socket (if serving) and takes care of all initialization in one step.

After initialization, it returns a struct libwebsocket_context * that represents this server. After calling, user code needs to take care of calling libwebsocket_service with the context pointer to get the server's sockets serviced. This can be done in the same process context or a forked process, or another thread,

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.

HTTP requests are sent always to the FIRST protocol in protocol, since at that time websocket protocol has not been negotiated. Other protocols after the first one never see any HTTP callack activity.

The server created is a simple http server by default; part of the websocket standard is upgrading this http connection to a websocket one.

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.

libwebsockets_get_protocol - Returns a protocol pointer from a websocket connection.

Arguments

wsi

pointer to struct websocket you want to know the protocol of

Description

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.

lws_set_log_level - Set the logging bitfield

Arguments

level

OR together the LLL_ debug contexts you want output from

log_emit_function

NULL to leave it as it is, or a user-supplied function to perform log string emission instead of the default stderr one.

Description

log level defaults to "err", "warn" and "notice" contexts enabled and emission on stderr.

libwebsocket_write - Apply protocol then write data to client

Arguments

wsi

Websocket instance (available from user callback)

buf

The data to send. For data being sent on a websocket connection (ie, not default http), this buffer MUST have LWS_SEND_BUFFER_PRE_PADDING bytes valid BEFORE the pointer and an additional LWS_SEND_BUFFER_POST_PADDING bytes valid in the buffer after (buf + len). This is so the protocol header and trailer data can be added in-situ.

len

Count of the data bytes in the payload starting from buf

protocol

Use LWS_WRITE_HTTP to reply to an http connection, and one of LWS_WRITE_BINARY or LWS_WRITE_TEXT to send appropriate data on a websockets connection. Remember to allow the extra bytes before and after buf if LWS_WRITE_BINARY or LWS_WRITE_TEXT are used.

Description

This function provides the way to issue data back to the client for both http and websocket protocols.

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.

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.

libwebsockets_serve_http_file - Send a file back to the client using http

Arguments

context

libwebsockets context

wsi

Websocket instance (available from user callback)

file

The file to issue over http

content_type

The http content type, eg, text/html

Description

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.

Returning <0 indicates error and the wsi should be closed. Returning >0 indicates the file was completely sent and the wsi should be closed. ==0 indicates the file transfer is started and needs more service later, the wsi should be left alone.

libwebsocket_client_connect - Connect to another websocket server

Arguments

context

Websocket context

address

Remote server address, eg, "myserver.com"

port

Port to connect to on the remote server, eg, 80

ssl_connection

0 = ws://, 1 = wss:// encrypted, 2 = wss:// allow self signed certs

path

Websocket path on server

host

Hostname on server

origin

Socket origin name

protocol

Comma-separated list of protocols being asked for from the server, or just one. The server will pick the one it likes best.

ietf_version_or_minus_one

-1 to ask to connect using the default, latest protocol supported, or the specific protocol ordinal

Description

This function creates a connection to a remote server

libwebsocket_client_connect_extended - Connect to another websocket server

Arguments

context

Websocket context

address

Remote server address, eg, "myserver.com"

port

Port to connect to on the remote server, eg, 80

ssl_connection

0 = ws://, 1 = wss:// encrypted, 2 = wss:// allow self signed certs

path

Websocket path on server

host

Hostname on server

origin

Socket origin name

protocol

Comma-separated list of protocols being asked for from the server, or just one. The server will pick the one it likes best.

ietf_version_or_minus_one

-1 to ask to connect using the default, latest protocol supported, or the specific protocol ordinal

userdata

Pre-allocated user data

Description

This function creates a connection to a remote server

callback - User server actions

Arguments

context

Websockets context

wsi

Opaque websocket instance pointer

reason

The reason for the call

user

Pointer to per-session user data allocated by library

in

Pointer used for some callback reasons

len

Length set for some callback reasons

Description

This callback is the way the user controls what is served. All the protocol detail is hidden and handled by the library.

For each connection / session there is user data allocated that is pointed to by "user". You set the size of this user data area when the library is initialized with libwebsocket_create_server.

You get an opportunity to initialize user data when called back with LWS_CALLBACK_ESTABLISHED reason.

LWS_CALLBACK_ESTABLISHED

after the server completes a handshake with an incoming client

LWS_CALLBACK_CLIENT_CONNECTION_ERROR

the request client connection has been unable to complete a handshake with the remote server

LWS_CALLBACK_CLIENT_FILTER_PRE_ESTABLISH

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

LWS_CALLBACK_CLIENT_ESTABLISHED

after your client connection completed a handshake with the remote server

LWS_CALLBACK_CLOSED

when the websocket session ends

LWS_CALLBACK_RECEIVE

data has appeared for this server endpoint from a remote client, it can be found at *in and is len bytes long

LWS_CALLBACK_CLIENT_RECEIVE_PONG

if you elected to see PONG packets, they appear with this callback reason. PONG packets only exist in 04+ protocol

LWS_CALLBACK_CLIENT_RECEIVE

data has appeared from the server for the client connection, it can be found at *in and is len bytes long

LWS_CALLBACK_HTTP

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. in points to the URI path requested and libwebsockets_serve_http_file 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.

LWS_CALLBACK_HTTP_WRITEABLE

you can write more down the http protocol link now.

LWS_CALLBACK_HTTP_FILE_COMPLETION

a file requested to be send down http link has completed.

LWS_CALLBACK_SERVER_WRITEABLE

If you call libwebsocket_callback_on_writable 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.

LWS_CALLBACK_FILTER_NETWORK_CONNECTION

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. in contains the connection socket's descriptor. 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.

LWS_CALLBACK_FILTER_PROTOCOL_CONNECTION

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. user is a pointer to an array of struct lws_tokens, you can use 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.

LWS_CALLBACK_OPENSSL_LOAD_EXTRA_CLIENT_VERIFY_CERTS

if configured for including OpenSSL support, this callback allows your user code to perform extra SSL_CTX_load_verify_locations or similar calls to direct OpenSSL where to find certificates the client can use to confirm the remote server identity. user is the OpenSSL SSL_CTX*

LWS_CALLBACK_OPENSSL_LOAD_EXTRA_SERVER_VERIFY_CERTS

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. user is the server's OpenSSL SSL_CTX*

LWS_CALLBACK_OPENSSL_PERFORM_CLIENT_CERT_VERIFICATION

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

http

//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, user is the x509_ctx, in is the ssl pointer and len 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.

LWS_CALLBACK_CLIENT_APPEND_HANDSHAKE_HEADER

this callback happens when a client handshake is being compiled. user is NULL, in is a char **, it's pointing to a char * which holds the next location in the header buffer where you can add headers, and len 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:

char **p = (char **)in;

if (len < 100) return 1;

*p += sprintf(*p, "Cookie: a=bx0dx0a");

return 0;

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.

Notice the callback is coming to protocols[0] all the time, because there is no specific protocol handshook yet.

LWS_CALLBACK_CONFIRM_EXTENSION_OKAY

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 in being the extension name, len is 0 and user is valid. Note though at this time the ESTABLISHED callback hasn't happened yet so if you initialize user content there, user content during this callback might not be useful for anything. Notice this callback comes to protocols[0].

LWS_CALLBACK_CLIENT_CONFIRM_EXTENSION_SUPPORTED

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].

LWS_CALLBACK_PROTOCOL_INIT

One-time call per protocol so it can do initial setup / allocations etc

LWS_CALLBACK_PROTOCOL_DESTROY

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.

The next four reasons are optional and only need taking care of if you will be integrating libwebsockets sockets into an external polling array.

LWS_CALLBACK_ADD_POLL_FD

libwebsocket deals with its poll 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

added to the polling loop

in contains the fd, and len is the events bitmap (like, POLLIN). If you are using the internal polling loop (the "service" callback), you can just ignore these callbacks.

LWS_CALLBACK_DEL_POLL_FD

This callback happens when a socket descriptor needs to be removed from an external polling array. in is the socket desricptor. If you are using the internal polling loop, you can just ignore it.

LWS_CALLBACK_SET_MODE_POLL_FD

This callback happens when libwebsockets wants to modify the events for the socket descriptor in in. The handler should OR len on to the events member of the pollfd struct for this socket descriptor. If you are using the internal polling loop, you can just ignore it.

LWS_CALLBACK_CLEAR_MODE_POLL_FD

This callback occurs when libwebsockets wants to modify the events for the socket descriptor in in. The handler should AND ~len on to the events member of the pollfd struct for this socket descriptor. If you are using the internal polling loop, you can just ignore it.

extension_callback - Hooks to allow extensions to operate

Arguments

context

Websockets context

ext

This extension

wsi

Opaque websocket instance pointer

reason

The reason for the call

user

Pointer to per-session user data allocated by library

in

Pointer used for some callback reasons

len

Length set for some callback reasons

Description

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.

Libwebsockets takes care of allocating and freeing "user" memory for each active extension on each connection. That is what is pointed to by the user parameter.

LWS_EXT_CALLBACK_CONSTRUCT

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 user.

LWS_EXT_CALLBACK_CLIENT_CONSTRUCT

same as LWS_EXT_CALLBACK_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.

LWS_EXT_CALLBACK_DESTROY

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 user) before the user data is deleted. This same callback is used whether you are in client or server instantiation context.

LWS_EXT_CALLBACK_PACKET_RX_PREPARSE

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. user is pointing to the extension's private connection context data, in 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.

LWS_EXT_CALLBACK_PACKET_TX_PRESEND

this works the same way as LWS_EXT_CALLBACK_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 in, 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.

struct libwebsocket_protocols - List of protocols and handlers server supports.

Members

name

Protocol name that must match the one given in the client Javascript new WebSocket(url, 'protocol') name

callback

The service callback used for this protocol. It allows the service action for an entire protocol to be encapsulated in the protocol-specific callback

per_session_data_size

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

rx_buffer_size

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 libwebsockets_remaining_packet_payload. Notice that you just talk about frame size here, the LWS_SEND_BUFFER_PRE_PADDING and post-padding are automatically also allocated on top.

owning_server

the server init call fills in this opaque pointer when registering this protocol with the server.

protocol_index

which protocol we are starting from zero

Description

This structure represents one protocol supported by the server. An array of these structures is passed to libwebsocket_create_server allows as many protocols as you like to be handled by one server.

struct libwebsocket_extension - An extension we know how to cope with

Members

name

Formal extension name, eg, "deflate-stream"

callback

Service callback

per_session_data_size

Libwebsockets will auto-malloc this much memory for the use of the extension, a pointer to it comes in the user callback parameter

per_context_private_data

Optional storage for this extension that is per-context, so it can track stuff across all sessions, etc, if it wants

struct lws_context_creation_info -

Members

port

Port to listen on... you can use 0 to suppress listening on any port, that's what you want if you are not running a websocket server at all but just using it as a client

iface

NULL to bind the listen socket to all interfaces, or the interface name, eg, "eth2"

protocols

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

extensions

NULL or array of libwebsocket_extension structs listing the extensions this context supports. If you configured with --without-extensions, you should give NULL here.

ssl_cert_filepath

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

ssl_private_key_filepath

filepath to private key if wanting SSL mode, else ignored

ssl_ca_filepath

CA certificate filepath or NULL

ssl_cipher_list

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"

gid

group id to change to after setting listen socket, or -1.

uid

user id to change to after setting listen socket, or -1.

options

0, or LWS_SERVER_OPTION_DEFEAT_CLIENT_MASK

user

optional user pointer that can be recovered via the context pointer using libwebsocket_context_user

ka_time

0 for no keepalive, otherwise apply this keepalive timeout to all libwebsocket sockets, client or server

ka_probes

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

ka_interval

if ka_time was nonzero, how long to wait before each ka_probes attempt