[exim] Need a little unix help

Some of you I'm srue are experts at this. I can probably get something
to work but I want to do it right. And it's fairly simple.

What I want to do is create a simple client/server application where
clients running Exim can easily report IP addresses to the server. The
server will accept the IP addresses and execute a command to add the IP
address to a MySQL database and increment a counter. What I'm
specifically doing is counting spam/ham based on IP address. But - if I
can just receive the IP address I'll figure put how to process it.

I have xinentd if that maes things easy.

On the client side I want to in an efficient way be able to pass a
string containing the IP address to the server. Maybe talk to an open port?

So - what's the simplest way to accomplish this?