Transferring files between 2 remote linux virtual machines

Me and my friend are trying to transfer files remotely using scp. We have both installed ssh server and turned it online but when trying to use the command nothing happens.
I am trying to transfer using his public ip.
It says it is listening on port 22, but I don’t know what is the problem.

You need to do three things:

1. Make sure in VirtualBox the network of the VM is set to bridged (you need to shut down the VM for this first). This will make the VM appear as a separate computer on the network, and make connecting to it more transparent.
2. Check the IP address of the VM (e.g. by running ip a inside the VM in a terminal)
3. Login to the web interface of your router and add a port forward to the IP you found and port 22.

Now you should be able to login from a remote host with ssh on your external IP (not the same as the VM’s IP!).