Mqtt protocol application: external network mobile phone control internal network raspberry pie

The experiment purpose ： Use the serial port of raspberry pie to output the string sent by the external network mobile phone
Don't understand MQTT For the of the agreement, please refer to ：MQTT Protocol experience Mosquitto Installation and use
Don't know how to use Python For the operation of raspberry pie serial port, please refer to ：Raspberry Pi B Of UART Minimalist routine

One 、 Preparation

1. The server is installed Mosquitto（MQTT Agent software ）;
2. Raspberry pie installed Python（ Used to write raspberry pie subscription code ）, And then use pip install paho-mqtt（ Realized MQTT Agreed Python expanded memory bank ）、wiringpi2（ Control raspberry pie IO Oral Python expanded memory bank ）;
3. The phone is installed MQTT Android client .

Two 、 Edit and run the raspberry pie subscription code

Edit and save the following code in raspberry pie as MQTT.py file , And add executable permissions , Then run with super user MQTT.py.

#!/usr/bin/env python
import paho.mqtt.client as mqtt
import wiringpi

#  Connect successfully callback function 
def on_connect(client, userdata, flags, rc):
    print("Connected with result code " + str(rc))
    #  After the connection is completed, subscribe serial The theme 
    client.subscribe("serial")

#  Message push callback function 
def on_message(client, userdata, msg):
    print(msg.topic+" "+str(msg.payload))
    #  Send the load through the serial port 
    wiringpi.serialPuts(serial,str(msg.payload))

if __name__ == '__main__':
    client = mqtt.Client()
    client.on_connect = on_connect
    client.on_message = on_message

    wiringpi.wiringPiSetup()
    serial = wiringpi.serialOpen('/dev/ttyAMA0',9600)

    try:
        #  Please change to yourself MQTT Public network of proxy server IP
        client.connect("192.168.1.107", 1883, 60)
        client.loop_forever()
    except KeyboardInterrupt:
        client.disconnect()
        wiringpi.serialClose(serial)

3、 ... and 、 Turn on the server MQTT Agency service , And use the mobile client to publish messages

Execute on server mosquitto command , function MQTT Agency service . Then open the MQTT Client mobile phone APP, Input MQTT Proxy server IP Address 、serial Subject and message content , Finally, click Publish, At this point, the serial port of raspberry pie will output the message content .

Four 、 Further study

Want to know paho-mqtt For more functions of the extension library, please refer to ：paho-mqtt 1.1 : Python Package Index
Want to know wiringpi2 For more functions of the extension library, please refer to ：WiringPi_WiringPi-Python: Python-wrapped version of Gordon Henderson’s WiringPi version 2.
Want to get more open source on the platform MQTT For the of the client, please refer to ：Paho - Open Source messaging for M2M