Well, I managed to solve my problem of network access by the various machines. It was quite simple in the end. Ubuntu now comes with a firewall application called ufw, the uncomplicated firewall. What I had forgotten was that it was enabled and it only allowed traffic in and out on port 80. So all I had to do was tell the firewall to open a port for ssh as defined in /etc/sshd_config and to allow connections from all machines on the local network.
Open a terminal and type:
sudo ufw statussudo ufw logging onsudo ufw allow <SSH port>sudo ufw allow from 192.168.0.0/16sudo ufw status
All you need now is a nice graphical front end so you don’t have to type into the terminal.
Now I can connect to the server and the desktop from the macbook via ssh and through the network shares defined in samba. I can drag and drop files between the various machines.