From Music Player Daemon Community Wiki

This page contains common connection problems, and how to fix them

[edit] FreeBSD 5.x

Due to a bug in versions prior to 0.12, mpd will only bind to an IPv6 address on various BSD systems. When you then try to connect via IPv4, it will fail. To resolve this, you can either disable IPv6 support in mpd (compile using ./configure --disable-ipv6), or disable IPv6 system wide (as root, run sysctl net.inet6.ip6.v6only=0).