Writing to a closed, local TCP socket not failing

Question

I seem to be having a problem with my sockets. Below, you will see some code which forks a server and a client. The server opens a TCP socket, and the client connects to i

Answer 1

After having called write() one (first) time (as coded in your example) after the client close()ed the socket, you'll be getting the expected EPIPE and SIGPIPE on any successive call to write().

Just try adding another write() to provoke the error:

...
printf( "Errno before: %s\n", strerror( errno ) );
printf( "Write result: %d\n", write( client_fd, "123", 3 ) );
printf( "Errno after:  %s\n", strerror( errno ) );

printf( "Errno before: %s\n", strerror( errno ) );
printf( "Write result: %d\n", write( client_fd, "A", 1 ) );
printf( "Errno after:  %s\n", strerror( errno ) );
...

The output will be:

Accepting
Server sleeping
Client closing its fd... Client exiting.
Errno before: Success
Write result: 3
Errno after:  Success
Errno before: Success
Client status is 0, server status is 13

The output of the last two printf()s is missing as the process terminates due to SIGPIPE being raised by the second call to write(). To avoid the termination of the process, you might like to make the process ignore SIGPIPE.