The general procedure is described in
I have encountered two cases where MPD on multiple nodes cannot communicate with each other:
- The firewall prevents such communication, and
- There are ambiguity in /etc/hosts.
For 1., we can disable iptables (the firewall commonly used in various Linux versions) and ufw (Ubuntu firewall) by the following commands:
sudo iptables -P INPUT ACCEPT
sudo iptables -P OUTPUT ACCEPT
sudo ufw disable
For 2., I just re-edit /etc/hosts to ensure all nodes are referred by their real IP addresses, instead of loop-back style addresses.