Networking feature for postgresql...

Hi,

I'm trying to add a -project specific- networking feature to my postgres
build (or database as function). What I want to do is to send a Query
instance (as a String-retrieved through an SPI function) to other
machines and (after they have executed it) to receive result tuples.
It's about a mediator-wrapper project. My first thought was to write 2
SPI functions (one for the server (concurrent) and the other for client)
but I'm not sure if this is going to work. I'm worried about setting up
the server process running on the background while other SPI calls are
made.

Can this be done? Should I consider something else first, before 
writting any code? 
Any suggestions would be appreciated!

Best regards,
Ntinos Katsaros