No way, extremely hard to do if not impossible.
First find out which port is open, then customize msn which is not open source.
Another way is to use yahoo messenger, which is supported by yahoo's own http proxy tunnel.
It automatically try all the way until finally try to use yahoo's "secret weapon".
最初由 bye 发布 don't understand whether the 2 VPN networks are like one single network that should not be a problem at all for two nodes within it to communicate.