（mqtt学习1）安装mosquitto代理者和客户端

1，介绍

mqtt是个网络协议，mosquitto是一个开源的mqtt broker，当然了它也有它的客户端，命令行和API都有，但是一般用它的命令行，而客户端API用paho的，paho是一个开源的mqtt client。很多人把mosquitto叫做服务器，只是为了好理解而已，事实上broker翻译过来是代理者。mqtt的工作原理，就是发布的客户端把话题和消息给broker，broker再转发给订阅的客户端。订阅客户端和发布客户端可以调换身份，而且不限制客户端的数量。

mosquitto 源码链接：https://github.com/eclipse/mosquitto

paho 源码链接 ： https://github.com/eclipse/paho.mqtt.c

2，安装代理者和客户端 

我这里是debian10.

guoyanzhang@debian:/etc/mosquitto$ sudo apt-get install mosquitto
guoyanzhang@debian:/etc/mosquitto$ sudo apt-get install mosquitto-clients

3， 启动mosquitto

guoyanzhang@debian:/etc/mosquitto$ sudo systemctl start mosquitto
guoyanzhang@debian:/etc/mosquitto$ sudo systemctl status mosquitto
● mosquitto.service - Mosquitto MQTT v3.1/v3.1.1 Broker
   Loaded: loaded (/lib/systemd/system/mosquitto.service; enabled; vendor preset: enabled)
   Active: active (running) since Wed 2020-05-20 21:38:10 HDT; 16s ago
     Docs: man:mosquitto.conf(5)
           man:mosquitto(8)
 Main PID: 28619 (mosquitto)
    Tasks: 1 (limit: 4915)
   Memory: 1.0M
   CGroup: /system.slice/mosquitto.service
           └─28619 /usr/sbin/mosquitto -c /etc/mosquitto/mosquitto.conf

4，配置mosquitto

guoyanzhang@debian:/etc/mosquitto$ ls
ca_certificates  certs  conf.d  mosquitto.conf
guoyanzhang@debian:/etc/mosquitto$ cat mosquitto.conf
# Place your local configuration in /etc/mosquitto/conf.d/
#
# A full description of the configuration file is at
# /usr/share/doc/mosquitto/examples/mosquitto.conf.example

pid_file /var/run/mosquitto.pid

persistence true
persistence_location /var/lib/mosquitto/

log_dest file /var/log/mosquitto/mosquitto.log

include_dir /etc/mosquitto/conf.d

guoyanzhang@debian:/etc/mosquitto$ cat conf.d/README
Any files placed in this directory that have a .conf ending will be loaded as
config files by the broker. Use this to make your local config.

开始都是在mosquitto.conf里面配置的（现在添加不生效），现在是在conf.d/下的xxx.conf文件里面配置，上面的README就是说，在conf.d目录下的所有的.conf文件都会被broker加载到配置文件中去，如下，我配置了bind_address：

guoyanzhang@debian:/etc/mosquitto$ cat conf.d/default.conf
bind_address 192.168.1.107

5，测试

订阅：

guoyanzhang@debian:/etc/mosquitto$ mosquitto_sub -t "test"
Error: Connection refused
guoyanzhang@debian:/etc/mosquitto$ mosquitto_sub -t "test" -h 192.168.1.107
hi mqtt

发布：

guoyanzhang@debian:~$ mosquitto_pub -t "test" -m "hi mqtt"
Error: Connection refused
guoyanzhang@debian:~$ mosquitto_pub -t "test" -m "hi mqtt" -h 192.168.1.107
guoyanzhang@debian:~$

这里的测试有Error是因为，开始broker绑定的ip是localhost，现在改成了192.168.1.107.