Implementation of the frontend protocol

Hi!

I'm developing a SQL proxy and I would like to implement the server
protocol used by Postgres, so the proxy may act like a PostgreSQL server
towards the clients.

I have read the nice and clean documentation of the protocol on
http://www.postgresql.org/docs/programmer/protocol.htm, but instead of
reimplementating the protocol I would like to reuse the current
implementation.

As far as I can tell from the protocol specification and the description
of how PostgreSQL processes a query (src/tools/backend/index.html) it is
implemented in or around src/backend/postmaster/postmaster.c and
src/backend/tcop/postgres.c - but I still have a bit of problems finding
my way around the sourcecode.

Could anyone direct me to the specific parts of the sourcecode dealing
with the frontend/backend protocol?

--
Bye, Peter Korsgaard