I'm coding for a linux platform using C. Let's say I have 2 threads. A and B.

A is an infinite loop and constantly trying to find out if there is data on the socket localhost:8080, where as B is a thread that spends most of its time in a blocked state until A calls mutex unlock function on a mutex that B uses to block itself. A will unlock B when it received appropriate data on the socket.

So you see here is a problem. B is "event driven" largely whereas A is in a constant running state. My target platform isn't resource rich so I wish A could be "activated" and enter running state only when it received data on socket, instead of constantly looping.

So how can I do that? If it matters - I wish to do this for both UDP and TCP sockets.

CodePudding user response：

There are Multiple was of doing what you want in a clean was. One approach, you are kind of using already, is a event system. A real event system would be overkill for the kind of problem you are dealing with, but can be found here. This is a (random) better implementation, capable of listening for multiple file descriptors and time based events, all in a single thread.

If you want to build one yourself, you should take a look at the select or poll function.

But I agree with @Jeremy Friesner, you should definitely use the functions made for socket programming, they are perfect for your kind of problem. Only use the event system approach if you really need it (with multiple sockets/timed events).

CodePudding user response：

You simply call recv (or recvfrom, recvmsg, etc) and it doesn't return until some data has been received. There's no need to "constantly try to find out if there is data" - that's silly.

If you set the socket to non-blocking mode then recv will return even if there's no data. If that's what you're doing, then the solution is simple: don't set the socket to non-blocking mode.