To connect real HP-IL devices you use real cables. For virtual IL devices you need matching IP port numbers. With VilMA it is now as simple as plugging real cables.
What is VilMA? It's a little REXX routine to handle virtual controllers (V41 or Emu71) and virtual HPIL devices, foremost those from Christoph Gießelink.
Alas, I have a problem. Distributing it is probably unlawful as I use a software classified "internal use only". So not to jeopardize the entire site hp41.org with a tiny but nasty zilch, I may only inform about what I've done. Just to give an example if someone likes to copy it.
Best,
M.