How to know if the client has terminated in sockets

Question

Suppose, I have a connected socket after writing this code..

if ((sd = accept(socket_d, (struct sockaddr *)&client_addr, &alen)) < 0)
{
    perror(\"a         


        

Answer 1

If the client program exits, then the OS on the client will close its end of the socket. When you call recv() it will return 0, or -1 with errno ECONNRESET if a TCP RST has been received (e.g. because you attempted to send data after the client had closed). If the whole client machine goes down, or the network becomes disconnected, then in that case you may not receive anything if the server is not trying to send anything; if that is important to detect, you can either send some data periodically, or set the SO_KEEPALIVE socket option using setsockopt() to force it to send a packet with no data after long periods (hours) of inactivity. When no acknowledgment is received, recv() will then return -1 with errno ETIMEDOUT or another error if more specific information is available.

In addition, if you attempt to send data on a socket that has been disconnected, by default the SIGPIPE signal will terminate your program. This can be avoided by setting the SIGPIPE signal action to SIG_IGN (ignore), or by using send() with the MSG_NOSIGNAL flag on systems that support it (Linux).