I am unable to send MIDI to virtual ports on Linux. I create virtual ports with the snd-virmidi command, and these are diplayed as "Virtual Raw MIDI 2-x" in acconectgui. In sendmidi, they appear as "VirMIDI 2-x". Nothing happens with either of these commands:
$ sendmidi virt "VirMIDI 2-0" on 60 100
$ sendmidi dev "VirMIDI 2-0" on 60 100
The Virtual MIDI port is connected to both Fluidsynth and aseqdump to monitor events. The virtual port is working because I can send MIDI there with amidi; for example:
$ amidi -p hw:2,0 -S "90 3C 7F"
plays a note. (Port hw:2,0 is Virtual Raw MIDI, 0.)