TL;DR

Using socat to listen on a local port and send the traffic to a remote host/port.

Often times I work in a Linux VM in a Mac (using VirtualBox), doing some remote connectivity from within the VM.

I’m lazy though, so I never fiddled too much with the graphics setup inside the VM. As a result, stuff in the browser might appear a bit little, and I like using the browser on the Mac side using some port mapping in VirtualBox.

Recently I wanted to see a remote destination to which I can connect only from the Linux VM. I was wondering on connecting to the VM via SSH and do some port forwarding, but then it occurred to me that socat could surely help me with this.

And it surely did:

socat TCP-LISTEN:54321,fork TCP:remote.example.com:12345

This opens local port 54321 listening for incoming connection, replicating and stitching them with a connection to port 12345 in remote host remote.example.com.

At this point, I only had to map local port 54321 from the Linux VM to the Mac and I could use the browser on the Mac to see remote.example.com:12345, passing through the connection set up by the VM.

I hope you can find this useful too, stay safe everybody!