if you're talking about the mpserver15, you can do this way:
http://mpmap02.flightgear.org/?fg_serve ... r.org,5001the server being interconnected was a theorical design, but what we see actually is a bit more of "good luck if you are on different mpservers"
some are competely invisible to others, and most of the time you only have the lazy relay at 1 packet every second.
just be sure to be on same server with the pilots you're on interaction with, and go to the "confidentials" ones if you have something to hide
jano