Using accept() and select() at the same time?

Question

I've got an event-driven network server program. This program accepts connections from other processes on other hosts. There may be many short-lived connections from different ports on the same remote IP.

Currently, I've got a while(1) loop which calls accept() and then spawns a thread to process the new connection. Each connection is closed after the message is read. On the remote end, the connection is closed after a message is sent.

I want to eliminate the overhead of setting up and tearing down connections by caching the open socket FDs. On the sender side, this is easy - I just don't close the connections, and keep them around.

On the receiver side, it's a bit harder. I know I can store the FD returned by accept() in a structure and listen for messages across all such sockets using poll() or select(), but I want to simultaneously both listen for new connections via accept() and listen on all the cached connections.

If I use two threads, one on poll() and one on accept(), then when the accept() call returns (a new connection is opened), I have to wake up the other thread waiting on the old set of connections. I know I can do this with a signal and pselect(), but this whole mess seems like way too much work for something so simple.

Is there a call or superior methodology that will let me simultaneously handle new connections being opened and data being sent on old connections?

Answer 1

Last time I checked, you could just listen on a socket and then select or poll to see if a connection came in. If so, accept it; it will not block (but you may want to really should set O_NONBLOCK just to be sure)

Answer 2

you could use listen then use select or poll then accept

if (listen(socket_fd, Number_connection) < 0 ) {     perror("listen");     return 1; } fd_set set; struct timeval timeout; int rv; FD_ZERO(&set); /* clear the set */ FD_SET(socket_fd, &set); /* add our file descriptor to the set */  timeout.tv_sec = 20; timeout.tv_usec = 0;  rv = select(socket_fd + 1, &set, NULL, NULL, &timeout); if (rv == -1) {     perror("select"); /* an error occurred */     return 1; } else if (rv == 0) {     printf("timeout occurred (20 second) \n"); /* a timeout occurred */     return 1; } else {     client_socket_fd = accept (socket_fd,(struct sockaddr *) &client_name, &client_name_len); }