Linux: is there a read or recv from socket with timeout?

You can use the setsockopt function to set a timeout on receive operations:

SO_RCVTIMEO

Sets the timeout value that specifies the maximum amount of time an input function waits until it completes. It accepts a timeval structure with the number of seconds and microseconds specifying the limit on how long to wait for an input operation to complete. If a receive operation has blocked for this much time without receiving additional data, it shall return with a partial count or errno set to [EAGAIN] or [EWOULDBLOCK] if no data is received. The default for this option is zero, which indicates that a receive operation shall not time out. This option takes a timeval structure. Note that not all implementations allow this option to be set.

// LINUXstruct timeval tv;tv.tv_sec = timeout_in_seconds;tv.tv_usec = 0;setsockopt(sockfd, SOL_SOCKET, SO_RCVTIMEO, (const char*)&tv, sizeof tv);// WINDOWSDWORD timeout = timeout_in_seconds * 1000;setsockopt(socket, SOL_SOCKET, SO_RCVTIMEO, (const char*)&timeout, sizeof timeout);// MAC OS X (identical to Linux)struct timeval tv;tv.tv_sec = timeout_in_seconds;tv.tv_usec = 0;setsockopt(sockfd, SOL_SOCKET, SO_RCVTIMEO, (const char*)&tv, sizeof tv);

Reportedly on Windows this should be done before calling bind. I have verified by experiment that it can be done either before or after bind on Linux and OS X.

Here's some simple code to add a time out to your recv function using poll in C:

struct pollfd fd;int ret;fd.fd = mySocket; // your socket handler fd.events = POLLIN;ret = poll(&fd, 1, 1000); // 1 second for timeoutswitch (ret) {    case -1:        // Error        break;    case 0:        // Timeout         break;    default:        recv(mySocket,buf,sizeof(buf), 0); // get your data        break;}

Install a handler for SIGALRM, then use alarm() or ualarm() before a regular blocking recv(). If the alarm goes off, the recv() will return an error with errno set to EINTR.