Attached is a replacement for /usr/local/plan9/src/lib9/post9p.c
(note that it says /lib9/ not /lib9p/!).  If you put that in, then you
should be able to just call threadpostmountsrv with a service 
of 'tcp!*!12345' or whatever you want. 

If you do this, then the service loop will be single-threaded
(as lib9p service loops always are) and the library will handle
feeding it messages from potentially many different active
connections.

Russ