I havea windows service built in .net which must build some hl7, send it off over tcp/ip, receive an ack. Are there any free libraries for doing this. I could probably handle the tcp/ip part myself, but if I can find a good library that at least has all the parsing logic to just deliver me a class instance representing the message that would save me a lot of work.
The post on Coding Headache is quite short. Here's another blog with some more information on nHapi that you could use. From a .Net perspective you could use Biztalk, that has some Hl7 support or use nHapi (that is an open source product).