Well, I'm looking for an "enterprise wide messaging queueing system" (EWMQS). The emphasis here is a system that provides a quick, clean api for transmitting information from one app and receiving it in another app. Granted you can do this with TCP/IP. It'll work for the first few apps, however it starts to break down when you scale up to n applications intercommunicating.

One of the first things that an EWMQS does is hide the details of platform specific byte level issues (big/little endian, 32/64 bit integer representation, etc).

Another issue is connection oriented vs channel oriented. TCP/IP is connection oriented. It requires both ends to be alive before communication can occur. The EWMQS solutions I mentioned above (JMS & MSMQ) allow you to establish a channel that receives messages independent of the application that will actually receive an process those messages. This gives a level of insulation between the sender and the receiver that can't happen with raw TCP/IP. OTOH it does eliminate the possibility for realtime communication

Perhaps more of an answer than you were looking for? Well, I anticipated this question and had prepared an explanation if the question was asked. ;)