Message Broker / System integration question

Need a general recommendation...

I have four systems I need to integrate. 2 have a queue based xml message api and 2 have web service api's. All interaction will be asynchronous.

Interaction is point to point to point

A => B
A <= B

Quite a bit of the interaction is conversational (long running)

A => B
     B => C
     B <= C
     B => D
          D => E
A <=========== E

Looking for some free (or nearly free) package or library that can help rather than do all this plumbing/infrastructure code from scratch. Took a peek at NServiceBus, however, after limited reading does not seem to be an exact fit.

Anyone have a recommendation on u开发者_高级运维sing NServiceBus for something like this or other alternatives rather than re-inventing the wheel.

We are a .Net shop.

Thanks..

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Sounds like the sagas in NServiceBus might be what you're looking for.

http://nservicebus.com/sagas.aspx

Can you give some more details on your business requirements?