 <p>RabbitMQ should fit your bill. The server is free and ready to use. You just need a client side to connect, push/send out message and get/pull notified message</p> <p>Server: <a href="http://www.rabbitmq.com/download.html" rel="nofollow">http://www.rabbitmq.com/download.html</a> Do a google for client or implement yourself</p> <p>Cheers</p>