Multipurpose relay (SOcket CAT).
- Listen to a port, wait for an incoming connection and transfer data to STDIO:
socat - TCP-LISTEN:8080,fork
- Create a connection to a host and port, transfer data in STDIO to connected host:
socat - TCP4:www.example.com:80
- Forward incoming data of a local port to another host and port:
socat TCP-LISTEN:80,fork TCP4:www.example.com:80