The Eclipse Paho project is rapidly becoming a source of some great MQTT clients – currently it contains implementations in C, Java, Javascript, Python (contributed from the mosquitto project), Lua, C++, embedded/minimal C, Go… and an Objective-C client is about to be added. The very popular mosquitto broker recently moved under the Eclipse umbrella too – the Eclipse Mosquitto project contains both mosquitto, and a fully open-sourced Really Small Message Broker from IBM, which also happens to support MQTT-SN.
EclipseCon 2014, coming up in March, has a strong focus on the Internet of Things.
As part of EclipseCon, the Eclipse Foundation is delighted to host an interoperability testing day for MQTT developers and vendors. The goal is to have representation from a wide range of MQTT brokers, clients, and MQTT-enabled devices. If you work with MQTT, take a look at the Eventbrite page to sign up for the interoperability testing, and check the Eclipse Paho wiki page for more infomation. If you are building APIs or devices on top of MQTT, this is a great way of interacting with the community, broadening awareness of your project or product, and making sure that things work smoothly for you users and customers!
Feel free to contact the Eclipse Paho team via their mailing list, if you have any questions.