I can vouch for qmidinet, but there is a but, it requires xwindows to run and display a funky little icon in the GUI...
If you are running headless (command line only) then
multimidicast http://llg.cubic.org/tools/multimidicast/ is your friend.
These tools support the ipMIDI windows protocol so it's quite possible to shunt midi out from a windows machine and play the midi out from raspberry pi's . MIDI Routing over IP . . .
I have generally made it a rule to run the Ethernet traffic over wired installations, it's been un-reliable over wireless, but this is a memory so anyone that know's better tell me that's the case in as rude a fashion as feel right !
I've used raspberry pi's in this fashion to route from a windows 98 machine controlling a Nord Modular over it's PC (MIDI) controller connection and the MIDI network can handle the Nord's MIDI based timing.
I forget it's in circuit whilst playing keyboards.
aconnect need configuring on startup for vanilla operation. aseqdump is your friend.