On Linux systems, Bonjour is implemented by the "Avahi" service. This is what McLaren Labs' rtpmidi program uses to find Apple MIDI services on your network when you set it up. Usually rtpmidi can find the iPhones and iPads on your network, but sometimes things do not go smoothly. That's when you need to do some network debugging. One of the tools that you can use to learn about Bonjour services on your network is avahi-browse.

When you use our rtpmidi tool to connect two devices you have created a "session." The session has an "initiator" side that started the connection, and "listener" side that accepted the invitation. Some devices, however, do not make good "initiators" and iPhones are a great example. An iPhone cannot initiate a network MIDI session.

A service is a program that the operating system automatically starts when it boots. On the Raspberry Pi "buster" operating system, the daemon that starts and stops services is called "systemd." You can read about creating services here:

Along with the recent release of McLaren Labs rtpmidi version 0.5.0, we have new ports to Raspberry Pi 4 Raspbian OS "Buster" and also Ubuntu 19.10 "Eoan Ermine".