Gsm800 mqtt library

问题:

I have sim800 module ,i want to control relay from webserver so i need mqtt library and sample code for arduino uno please help to me,What is AT command for publish and subscribe the tag in sim800 using arduino uno

回答1:

I think it is very unlikely that your SIM800 module will have an AT command for MQTT.

There are a couple of MQTT libraries for Arduino:

• AdaFruit: https://github.com/adafruit/Adafruit_MQTT_Library
• PubSubClient by Nick O'Leary: http://pubsubclient.knolleary.net/

Both of these libraries should work with any library than implements the Client interface. So it should be possible to create a TCP client that talks to the GSM module.

If the SIM800 supports the GSM library then that implements the Client interface: https://www.arduino.cc/en/Reference/GSM

If you are using the hardware serial port in the Arduino, you might be better using a Leonardo than a Uno, because you can use the USB to programme the Arduino, and the hardware serial to talk to the GSM module.

回答2:

You can try using Paho Arduino client library. It features full fledged MQTT library with support to MQTT 3.1, MQTT 3.1.1 & SSL/TLS.

回答3:

MQTT Library for SIM800 GSM Modem is available at ElementzTechBlog, ElementzGithubRepository,ElementzOnlineCart

Functionalities:

Auto connect

   Automatically connect to TCP and to MQTT server.

connect function

   This function can be used to connect your client to MQTT broker.
   Use only if you do not use Auto connect functionality.
   Optionally  you can use username, password, WILL topic and WILL Message.

OnConnect CallBack function

   This call back function is called when MQTT connection is established.
   You can call subscription and publish functions inside it (according to your need).

publish function

   This function can be used to publish messages to different topics.
   You can select  QoS levels and RETAIN flag according to your need.

subscribe function

   This function can be used to subscribe messages from different topics.

OnMessage CallBack function

   This callback function is called when messages are received from  subscribed topics
   Topic, TopicLength, Message, MessageLength are the arguments of  OnMessage callback function.
   Inside this, you can write your custom code.

unsubscribe function

   This function can be used to unsubscribe from a previously subscribed topic.

disconnect function

   This function can be used to disconnect your client from MQTT broker.

Keep Alive

   You can specify your KeepAlive duration while initializing.
   Ping requests are sent and received automatically.