Shulou(Shulou.com)06/03 Report--

MQTT, as a message middleware, is a "lightweight" communication protocol based on publish/subscribe mode, which is built on TCP/IP protocol.

The biggest advantage of MQTT is that it can provide real-time reliable messaging services for connecting remote devices with very little code and limited bandwidth. As a low-overhead, low-bandwidth instant messaging protocol, it has a wide range of applications in the Internet of Things, small devices, mobile applications and so on. MQTT Protocol A protocol designed to communicate with remote sensors and control devices over low-bandwidth, unreliable networks. It has the following key characteristics

(1) Use the publish/subscribe messaging pattern to provide one-to-many message publishing and decoupling of applications.

(2) Message transmission shielded from payload content.

(3) Provide network connectivity using TCP/IP.

The mainstream MQTT is based on TCP connections for data push, but there is also a UDP-based version called MQTT-SN. These two versions are based on different connection methods, and their advantages and disadvantages are naturally different.

(4) There are three types of quality of service for messaging:

"At most once," message publication depends entirely on the underlying TCP/IP network. Message loss or duplication can occur. This level can be used in cases where environmental sensor data is not important for a lost read record because a second transmission will occur shortly. This method is mainly the push of ordinary APP. If your smart device is not connected to the Internet when pushing messages, the push is not received in the past, and the Internet will not be received again.

"At least once," ensuring that messages arrive, but message duplication may occur.

"Only once," make sure the message arrives once. This level can be used in some demanding billing systems. In billing systems, duplicate or missing messages can lead to incorrect results. This highest-quality messaging service can also be used to push instant messaging apps, ensuring that users receive it and only receive it once.

(5) Small transmission, low overhead (fixed-length header is 2 bytes), protocol switching minimized to reduce network traffic.

This is why the introduction says it is very suitable for "communication between sensors and servers and collection of information in the field of Internet of Things." It is necessary to know that the computing power and bandwidth of embedded devices are relatively weak, and it is very suitable to use this protocol to transmit messages.

(6) A mechanism for notifying interested parties of unexpected client outages using the Last Will and Testament features.

Last Will: A last will mechanism used to notify other devices under the same topic that the device that sent the last will has disconnected.

Testament: A mechanism similar to Last Will.

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.