ZeroMQ

http://blog.pythonisito.com/2012/08/distributed-systems-with-zeromq.html

One of the first things to understand about ZeroMQ is that it's not a message broker like you might assume from its name. ZeroMQ is a library that supports certain network communication patterns using sockets. The "MQ" part comes in because ZeroMQ uses queues internally to buffer messages so that you don't block your application when sending data.

http://blog.pythonisito.com/2012/08/zeromq-flow-control-and-other-options.html