Ø The socket library that acts as a concurrency framework.
Ø Carries messages across inproc, IPC, TCP, and multicast.
Ø Connect N-to-N via fanout, pubsub, pipeline, request-reply.
Ø Asynch I/O for scalable multicore message-passing apps.
Ø Large and active open source community.
Ø 40+ languages including C, C++, Java, .NET, Python.
Ø Most OSes including Linux, Windows, OS X.
Ø Free software with full commercial support.