socat

Multipurpose relay (SOcket CAT). More information: http://www.dest-unreach.org/socat/.

• Listen to a port, wait for an incoming connection and transfer data to STDIO:
  socat - TCP-LISTEN:8080,fork
• Listen on a port using SSL and print to STDOUT:
  socat OPENSSL-LISTEN:4433,reuseaddr,cert=./cert.pem,cafile=./ca.cert.pem,key=./key.pem,verify=0 STDOUT
• 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