Hi there,
thanks for the guide - this is exactly what i also wanted to setup.
Sadly linux audio (especially jack) is to me like black magic.
I tried setting up the virtual port to no avail. I created ~/.asoundrc as user ‘patch’, /root/.asoundrc and /etc/asound.conf (always pasted your config), but aplay -l never listed the port “jackplug”.
I tried testing the port (even if it isn’t listed) with speaker-test -D jackplug but only got an error: Playback open error: -6,No such device or address
Any chance you could help me get this running?
Thanks in advance 
Edit:
Seems like i’m missing some libs (i think it’s “alsa-plugins”)… 
root@pisound > /root# speaker-test -c 2 -D jackplug
speaker-test 1.1.8
Playback device is jackplug
Stream parameters are 48000Hz, S16_LE, 2 channels
Using 16 octaves of pink noise
ALSA lib dlmisc.c:287:(snd1_dlobj_cache_get) Cannot open shared library /usr/lib/arm-linux-gnueabihf/alsa-lib/libasound_module_pcm_jack.so ((null): /usr/lib/arm-linux-gnueabihf/alsa-> lib/libasound_module_pcm_jack.so: cannot open shared object file: No such file or directory)
Playback open error: -6,No such device or address
Sadly there’s no “alsa-plugins” package in raspbians repository. Will try to compile it myself.