I have been spoiled by the ease with which I can connect my iPad up to MIDI applications on my Macbook using the native support for midi-over-the-network (apparently RTP-MIDI) provided by the CoreMIDI subsystem in both OS X and iOS.
Is there a compatible Linux implementation? I have found some tantalizing references out there that indicate there may be one, but I haven't been able to find any concrete information.
The original reference implementation of the RTP-MIDI protocol (originally specified in RFC4695 - now updated to RFC6295) from the guys who developed it is available as part of an older version of their sfront software.
It seems that the Wikipedia page on RTP-MIDI now has a good list available implementations.
A more up to date implementation is available in the Java based nmj library, which apparently works with iOS: http://www.humatic.de/htools/nmj
There was (now defunct) the interesting scenic project that contains Python based rtpmidi support (from which the now discontinued midistream Debian package was derived). In the Scenic source tree the actual midistream python application is here scenic/py/scripts/midistream.in, and the associated library may be found here: scenic/py/rtpmidi
It is also possible to use JACK to send MIDI but you need to run JACK on all machines (so for iOS you'll need an app that supports JACK).
Some more Windows based software (free but not open source): http://www.tobias-erichsen.de/software.html
Update 2018: There's now a Node based implementation of rtpMIDI and also the Arduino-AppleMIDI-Library that may be possible to port to Linux.
Update 2019: A new implementation aimed at the Raspberry Pi called RaveloxMIDI has become available which seems like it will run on Debian/Centos Linux as well.
Update 2020: Another Linux RTP-MIDI library: rtpmidid and a Python based one: pymidi
One other alternative is to use a MIDI router box with USB-MIDI and Ethernet (RTP-MIDI) interfaces. You attaches the USB connection to your linux machine just like any USB/MIDI interfaces. Then, data received on the virtual USB MIDI ports are forwarded to the opened RTP-MIDI sessions (and vice-versa) by the box. At least, one product (Cinara MidiGateway) is doing that kind of functions. This solution does not require any kind of specific software running on the host, and it preserves compatibility with other RTP-MIDI devices.
Looks like several iConnectivity products are set up to do turnkey RTP-MIDI (Ethernet MIDI) as well.
