Built-in service loop entry

Functions
LWS_VISIBLE LWS_EXTERN int	lws_service (struct lws_context *context, int timeout_ms)
LWS_VISIBLE LWS_EXTERN int	lws_service_tsi (struct lws_context *context, int timeout_ms, int tsi)
LWS_VISIBLE LWS_EXTERN void	lws_cancel_service_pt (struct lws *wsi)
LWS_VISIBLE LWS_EXTERN void	lws_cancel_service (struct lws_context *context)
LWS_VISIBLE LWS_EXTERN int	lws_service_fd (struct lws_context *context, struct lws_pollfd *pollfd)
LWS_VISIBLE LWS_EXTERN int	lws_service_fd_tsi (struct lws_context *context, struct lws_pollfd *pollfd, int tsi)

Detailed Description

Built-in service loop entry

If you're not using libev / libuv, these apis are needed to enter the poll() wait in lws and service any connections with pending events.

Function Documentation

LWS_VISIBLE LWS_EXTERN void lws_cancel_service

(

struct lws_context *

context

)

#include <lib/libwebsockets.h>

lws_cancel_service() - Cancel wait for new pending socket activity

Parameters

context

Websocket context This function let a call to lws_service() waiting for a timeout immediately return. What it basically does is provide a fake event that will be swallowed, so the wait in poll() is ended. That's useful because poll() doesn't attend to changes in POLLIN/OUT/ERR until it re-enters the wait.

LWS_VISIBLE LWS_EXTERN void lws_cancel_service_pt

(

struct lws *

wsi

)

#include <lib/libwebsockets.h>

lws_cancel_service_pt() - Cancel servicing of pending socket activity on one thread

Parameters

wsi

Cancel service on the thread this wsi is serviced by This function lets a call to lws_service() waiting for a timeout immediately return. It works by creating a phony event and then swallowing it silently. The reason it may be needed is when waiting in poll(), changes to the event masks are ignored by the OS until poll() is reentered. This lets you halt the poll() wait and make the reentry happen immediately instead of having the wait out the rest of the poll timeout.

LWS_VISIBLE LWS_EXTERN int lws_service	(	struct lws_context *	context,
		int	timeout_ms
	)

#include <lib/libwebsockets.h>

lws_service() - Service any pending websocket activity

Parameters

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.

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.

LWS_VISIBLE LWS_EXTERN int lws_service_fd	(	struct lws_context *	context,
		struct lws_pollfd *	pollfd
	)

#include <lib/libwebsockets.h>

lws_service_fd() - Service polled socket with something waiting

Parameters

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

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

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 lws_service_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.

LWS_VISIBLE LWS_EXTERN int lws_service_fd_tsi	(	struct lws_context *	context,
		struct lws_pollfd *	pollfd,
		int	tsi
	)

#include <lib/libwebsockets.h>

lws_service_fd_tsi() - Service polled socket in specific service thread

Parameters

context	Websocket context
pollfd	The pollfd entry describing the socket fd and which events happened.
tsi	thread service index

Same as lws_service_fd() but used with multiple service threads

LWS_VISIBLE LWS_EXTERN int lws_service_tsi	(	struct lws_context *	context,
		int	timeout_ms,
		int	tsi
	)

#include <lib/libwebsockets.h>

lws_service() - Service any pending websocket activity

Parameters

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.

Same as lws_service(), but for a specific thread service index. Only needed if you are spawning multiple service threads.