MIDIThru=umidi1,udp Network Midi Thru isn't making sound

[RK11111111111]

If I set MIDIThru using rtpmidi, MiniDexed network sends midi and I can see it on a remote computer, however when I do this it does not make a sound. I can disable this rtpMIDI connects but doesn't send the midi from the keyboard. It just sends the midi. Even if the network is not connected, the synth doesn't make a sound.

MIDIThru=umidi1,udp

Just for completeness. I want to be able to record the midi I play at the keyboard live while it is making sound, then play it back with a midi sequencer.