非阻塞select（）？

Question

I'm trying to implement simple networking game (client - server) which uses UDP to transfer game events over network, and I have this working well, but now I would like to add to game chat over tcp in same console application. I've tried to implement multi client chat using select() and non-blocking master socket. Chat is working as standalone application but I have problems putting it together.

Basically my server loop looks like this:

while(true)
{
    sendUDPdata()
    ...

    while(true)
    {
        receiveUDPdata()
    }
}

Problem is that when I want to add chat to server's main loop (handling UDP) like this:

while(true)
{
    HandleTCPConnections();

    sendUDPdata();
    ...

    while(true)
    {
        receiveUDPdata();
    }
}

calling select() in HandleTCPConnections() blocks whole server. Is there any way how to handle this?

Answer 1

There are two good ways to do this:

1. Use threads. Have a thread to handle your TCP sockets and a thread to handle your UDP sockets.

2. Use a reactor. Both the UDP code and the TCP code register their sockets with the reactor. The reactor blocks on all the sockets (typically using poll ) and calls into the appropriate code when activity occurs on that socket.

There are lots of libraries out there for both of these options (such as libevent and boost.asio ) that you can use if you don't want to reinvent the wheel.

Answer 2

select is a blocking call if there's no data available from the sockets, in your case.

Your chat can either run along with the server or in parallel with it: you've already got the first case; for the second, you'd better go for a separate thread that handles the chat. C++ has <thread> , which you may want to look into.

A separate thread is easier to implement in this case because you've a separate connection, and separate sockets therefore, that would otherwise need to be looked after for concurrent access.