General

Port forwarding with socat is a technique that allows the user to forward network traffic from one network to another using the socat tool. Socat is a command-line utility that enables the user to establish network connections and perform various types of network operations, including port forwarding.

Commands

The basic syntax to perform port forwarding using socat is much simpler. If we wanted to open port 3389 on a host and forward any connection we receive there to port 3389 on host 1.1.1.1, you would have the following command:

Run on the Intermediary Machine

socat TCP4-LISTEN:3389,fork TCP4:1.1.1.1:3389

We might need to open the firewall

netsh advfirewall firewall add rule name="Open Port 3389" dir=in action=allow protocol=TCP localport=3389

The fork option allows socat to fork a new process for each connection received, making it possible to handle multiple connections without closing. If you don't include it, socat will close when the first connection made is finished.