Socat

socat [options] <address> <address>

You have to provide both addresses for it to work, each address will be made up like this

protocol:ip:port

Examples showing the same functionality as Netcat

nc localhost 80
socat - TCP4:localhost:80 
OR 
socat STDIN TCP4:localhost:80

nc -lp localhost 700
socat TCP4-LISTEN:700 STDOUT

nc -lp localhost 700 -e /bin/bash
socat TCP4-LISTEN:700 EXEC:/bin/bash

We can go beyond Netcat with some SSL examples, but first, we need to generate an SSL cert for the server. Generate an SSL cert

openssl req -new -x509 -days 365 -nodes -out cert.pem -keyout cert.key

SSL server

socat OPENSSL-LISTEN:443,cert=/cert.pem -

SSL client

socat - OPENSSL:localhost:443

Both addresses don’t have to use the same protocol, so you can do ssl server -> non-ssl server. You should also check out the options that you can apply, for example you can use fork to tell socat to listen and handle multiple clients.

socat TCP4-LISTEN:5000,fork OPENSSL:localhost:443

Finally if you are tunnelling a connection between servers using socat you can use the -v option to print all the traffic to stdout.