Connect/Disconnect Serial ports (uart) on-the-fly via controlvm

[Jim Ramsay]

There doesn't seem to be any way to connect or disconnect Serial Devices on-the-fly.

Obviously I cannot add a *new* serial port while a VM is running, but I would expect that I should be able to change an existing serial port from "disconnected" to "server" to "client" to "file" to a raw device whenever I like, just like I can already simulate a network cable disconnect via the GUI or 'VBoxManage controlvm setlinkstate'

This is important to me because I often have my laptop connected to a docking station, and to undock I must close all open COM ports -> Having a uart configured in a runnig VM counts as "open", so I must shut down my VMs before I can undock my PC. This is of course less than optimal.

With VMWare I could simply mark the serial port as "disconnected" before undocking: To the Guest it appears that I pulled out the serial cable, no input, no output. The host would of course close the COM port and allow me to undock.