C Sockets: Avoiding garbage when socket is closed

Question

I'm programming a server and a client using non blocking sockets (fd_sets and select function) and once the server closes or shuts down a client socket, the client starts receiving a lot of garbage until it crashes.. I've been warned that when working with select() a socket would become readable when the connection was terminated, but how can I know in

if( FD_ISSET( socket, &read ) ) 
{
} 

if the cause is just regular data or the connection has ended?

Thank you a lot!

Answer 1

The file descriptor sets wont tell you if the socket is closed, only that you may attempt to read from it. When the remote end closes the connection the socket will become "readable". When you attempt a recv() the return value will be 0 indicating the socket is closed. Always check your return values.