Using HTTP for an IM system

Question

hi, Im new to C#. Im in 4th year of my commercial software development degree and for our project we are going to develop a IM system. It will consist mainly of a client, (c#) a server and a DB. We were going to use TCP for communication between client and server but it seems that we will most likely not be allowed/unable to do so because of college computer security and the way most ports are blocked. (a port scan shows 5 open ports) Our project advisor recommended we use HTTP to communicate between client/server. After searching the web for hours, I can only see ways of getting web pages thru http. I just want to send raw data, be it string objects or whatever. Im new to networking and to c#, but very willing to learn :-) Ive also come across SOAP (simple object access protocol) but I cant really understand how this is implemented into a program. Also, it seems that by using http in my program, i can only connect to web services, such as ASP or possibly Java Servlets. Any help on how I would, for example, get the message "hello world" from a client to a server and back using HTTP would be greatly appreciated. We are reasonably open on what technology/language to use in the server. Thanks. :-)