树莓派上安装 Mosquitto 实现 MQTT

1 在树莓派上安装Mosquitto

在树莓派上安装Mosquitto和其他平台类似，如果在树莓派平台直接编译时间可能会稍长些。Mosquitto源代包不大，所以编译时间尚可忍受。

2 安装

截止2014年9月，最新版本为mosquitto-1.3.4。在树莓派中新建一个目录，例如software

# 下载源代码包
wget http://mosquitto.org/files/source/mosquitto-1.3.4.tar.gz
# 解压
tar zxfv mosquitto-1.3.4.tar.gz
# 进入目录
cd mosquitto-1.3.4
# 编译
make
# 安装
sudo make install

2.2 安装注意点

编译找不到openssl/ssl.h
解决方法：安装openssl

sudo apt-get install libssl-dev

编译过程找不到ares.h
解决方法：修改config.mk中的WITH_SRV:=yes，改为WITH_SRV:=yes

使用过程中找不到libmosquitto.so.1
error while loading shared libraries: libmosquitto.so.1: cannot open shared object file: No such file or directory

解决方法：修改libmosquitto.so位置

# 创建链接
sudo ln -s /usr/local/lib/libmosquitto.so.1 /usr/lib/libmosquitto.so.1
# 更新动态链接库
sudo ldconfig

make: g++：命令未找到
解决方法：安装g++编译器

sudo apt-get install g++

3 简单的例子

设计一个简单的测试案例，在PC机上运行MQTT代理服务器，而树莓派订阅主题为gpio的消息，PC机发布同主题消息，消息的内容为JSON数据包，数据包格式为{“index”:17,“value”:0}，index代表树莓派GPIO的编号，value代表打开或关闭状态。

image.png

本例中PC机IP地址为 192.168.1.110，树莓派的IP地址为192.168.1.106

3.1在PC机中开启MQTT服务

mosquitto -v

3.2 在树莓派中订阅消息

mosquitto_sub -v -t gpio -h 192.168.1.110

3.3 在PC机中发布消息

mosquitto_pub -t gpio -h 192.168.1.110 -m "{\"pin\":17,\"value\":0}"
#-h指定MQTT代理服务器主机，指向PC机IP地址192.168.1.110

3.4 消息被推送到树莓派中

最后在树莓派中输出以下内容:

gpio {"index":17,"value":0}

在PC机MQTT服务器控制台中输出

1410600001: mosquitto version 1.3.4 (build date 2014-09-13 15:55:06+0800) starting
1410600001: Using default config.
1410600001: Opening ipv4 listen socket on port 1883.
1410600001: Opening ipv6 listen socket on port 1883.
1410600062: New connection from 192.168.1.106 on port 1883.
1410600062: New client connected from 192.168.1.106 as mosqsub/3063-raspberryp (c1, k60).
1410600062: Sending CONNACK to mosqsub/3063-raspberryp (0)
1410600062: Received SUBSCRIBE from mosqsub/3063-raspberryp
1410600062: gpio (QoS 0)
1410600062: mosqsub/3063-raspberryp 0 gpio
1410600062: Sending SUBACK to mosqsub/3063-raspberryp
1410600122: Received PINGREQ from mosqsub/3063-raspberryp
1410600122: Sending PINGRESP to mosqsub/3063-raspberryp
1410600152: New connection from 192.168.1.110 on port 1883.
1410600152: New client connected from 192.168.1.110 as mosqpub/9793-EasyARM (c1, k60).
1410600152: Sending CONNACK to mosqpub/9793-EasyARM (0)
1410600152: Received PUBLISH from mosqpub/9793-EasyARM (d0, q0, r0, m0, 'gpio', ... (22 bytes))
1410600152: Sending PUBLISH to mosqsub/3063-raspberryp (d0, q0, r0, m0, 'gpio', ... (22 bytes))
1410600152: Received DISCONNECT from mosqpub/9793-EasyARM
1410600182: Received PINGREQ from mosqsub/3063-raspberryp
1410600182: Sending PINGRESP to mosqsub/3063-raspberryp

4使用MQTT远程控制GPIO

下面借助python-gpio扩展库，通过消息推送的方式实现GPIO端口的远程控制。

4.1 安装paho-mqtt

使用pip工具安装paho-mqtt，输入以下指令即可

sudo pip install paho-mqtt

4.2 树莓派订阅代码 simple.py

# -*- coding: utf-8 -*-  
import paho.mqtt.client as mqtt
import RPi.GPIO as GPIO
import json
  
# BCM GPIO编号
pins = [17,18,27,22,23,24,25,4]
def gpio_setup():
    # 采用BCM编号
    GPIO.setmode(GPIO.BCM)
    # 设置所有GPIO为输出状态，且输出低电平
    for pin in pins:
        GPIO.setup(pin, GPIO.OUT)
        GPIO.output(pin, GPIO.LOW)
         
def gpio_destroy():
    for pin in pins:
        GPIO.output(pin, GPIO.LOW)
        GPIO.setup(pin, GPIO.IN)
         
# 连接成功回调函数
def on_connect(client, userdata, flags, rc):
    print("Connected with result code " + str(rc))
    # 连接完成之后订阅gpio主题
    client.subscribe("gpio")
  
# 消息推送回调函数
def on_message(client, userdata, msg):
    print(msg.topic+" "+str(msg.payload))
    # 获得负载中的pin 和 value
    gpio = json.loads(str(msg.payload))
  
    if gpio['pin'] in pins:
        if gpio['value'] == 0:
            GPIO.output(gpio['pin'], GPIO.LOW)
        else:
            GPIO.output(gpio['pin'], GPIO.HIGH)
  
if __name__ == '__main__':
    client = mqtt.Client()
    client.on_connect = on_connect
    client.on_message = on_message
    gpio_setup()
     
    try:
        # 请根据实际情况改变MQTT代理服务器的IP地址
        client.connect("192.168.1.110", 1883, 60)
        client.loop_forever()
    except KeyboardInterrupt:
        client.disconnect()
        gpio_destroy()

4.3 启动服务并发布消息

在PC机中启动MQTT代理服务

mosquitto -v

在树莓派中运行脚本

sudo python simple.py

在PC机中发布消息

# 打开GPIO17
mosquitto_pub -h 192.168.1.110 -t gpio -m "{\"pin\":17,\"value\":1}"
# 关闭GPIO17
mosquitto_pub -h 192.168.1.110 -t gpio -m "{\"pin\":17,\"value\":0}"

运行结果
树莓派GPIO17根据PC机推送的消息点亮或熄灭。