协议地址：http://public.dhe.ibm.com/software/dw/webservices/ws-mqtt/mqtt-v3r1.html
当然也有PDF版的，百度一下，不过个人感觉不是官网上的字体和排版最舒服。
那么这个协议是用做什么或有什么特色呢？下面是mqtt.org上的首段介绍：
It was designed as an extremely lightweight publish/subscribe messaging transport. It is useful for connections with remote locations where a small code footprint is
required and/or network bandwidth is at a premium. For example, it has been used in sensors communicating to a broker via satellite link, over occasional dial-up connections with healthcare providers, and in a range of home automation and small device scenarios.
It is also ideal for mobile applications because of its small size, low power usage, minimised data packets, and efficient distribution of information to one or many receivers
MQTT是轻量级基于代理的发布/订阅的消息传输协议，它可以通过很少的代码和带宽和远程设备连接。例如通过卫星和代理连接，通过拨号和医疗保健提供者连接，以及在一些自动化或小型设备上，而