Hassio and socat

Following on from this and this post…

How can I install socat in Hassio?

Let me be more specific: I downloaded the Hassio VHDX file and it’s running nicely as a virtual machine. I installed the SSH plugin as per here, so I can now access the command line, but if I try to run socat from there, I get

-bash: socat: command not found

Even more detail: I’m already serving an RFXCom device plugged into a Windows box using a nifty little prog called Comm Tunnel (as the server) and I have Node-RED running in Ubuntu, which runs socat (as the endpoint) as a system service. This works nicely. Now I want to serve a Z-Wave dongle also plugged into the Windows machine, but I want my new Hassio VM to be the endpoint. Luckily the Z-Wave dongle is actually a serial device that shows up in Device Manager (win) as COM4, so I can hopefully do the same thing.