Open Sound Control is a more efficient replacement of Midi over an udp network. Applications sending OSC include Ircam's Open Music.
Both OSCMidicPlayer and the OSC sending application have to use the same udp port.
verify in the OSC sending application on which udp port it is sending. By default, Open Music uses port 3000
select Preferences… from the OSCMidicPlayer menu
click on the OSC tab
type the udp port in the UDP Port In field, followed by a tab
if you want to use OSCMidicPlayer as microplayer with Open Music, you need to type the talk back port in the UDP Port Out field as well, followed by a tab