c++ - Setting timeout to recv function

Question

I read from socket using recv function. I have problem when no data available for reading. My programm just stops. I found that I can set timeout using select function. But looks that timeout affects select function itself and recv that goes after select still waits uncontinuously.

fd_set set;
struct timeval timeout;
FD_ZERO(&set); /* clear the set */
FD_SET(s, &set); /* add our file descriptor to the set */
timeout.tv_sec = SOCKET_READ_TIMEOUT_SEC;
timeout.tv_usec = 0;
int rv = select(s, &set, NULL, NULL, &timeout);
if((recv_size = recv(s , rx_tmp , bufSize ,0)) == SOCKET_ERROR)
      {
      ...
      }

How to ask recv function return after some timout?

Answer 1

Another way to set a timeout on recv() itself without using select() is to use setsockopt() to set the socket's SO_RCVTIMEO option (on platforms that support it).

On Windows, the code would look like this:

DWORD timeout = SOCKET_READ_TIMEOUT_SEC * 1000;
setsockopt(s, SOL_SOCKET, SO_RCVTIMEO, (char*)&timeout, sizeof(timeout));

//...

recv_size = recv(s, rx_tmp, bufSize, 0);
if (recv_size == SOCKET_ERROR)
{
    if (WSAGetLastError() != WSAETIMEDOUT)
        //...
}

On other platforms, the code would look like this instead:

struct timeval timeout;
timeout.tv_sec = SOCKET_READ_TIMEOUT_SEC;
timeout.tv_usec = 0;
setsockopt(s, SOL_SOCKET, SO_RCVTIMEO, &timeout, sizeof(timeout));

//...

recv_size = recv(s, rx_tmp, bufSize, 0);
if (recv_size == -1)
{
    if ((errno != EAGAIN) && (errno != EWOULDBLOCK))
        //...
}