Is there a way to detect that TCP socket has been closed by the remote peer, without reading from it?

Question

First, a little background to explain the motivation: I\'m working on a very simple select()-based TCP \"mirror proxy\", that allows two firewalled clients to talk to each

Answer 1

You could check if the socket is still connected by trying to write to the file descriptor for each socket. Then if the return value of the write is -1 or if errno = EPIPE, you know that socket has been closed.
for example

int isSockStillConnected(int *fileDescriptors, int numFDs){
     int i,n;
     for (i=0;i