HTTP / XML Project help required

Hi All I have had a project dumped in my lap and would appreciate some thoughts, guidance, ideas from the members of the list. I have to develop a listener that sits waiting and when it receives a request it has to send a message using a HTTP POST to a URL. I know the URL and the port (not 80 as that would be too easy). The message starts with a custom HTTP header and I know the 12 items that must be in the header. The message then contains a block which is a request to the server we are posting to. The whole process then receives a response which looks very much like the message being POSTed to it. I don't have any trouble bulding the body of the message as it is really just a string building exercise. What I have no experience with is the HTTP POST side of things. I would appreciate any thoughts on ways of achieving what I have to do. Regards Richard