（mqtt學習1）安裝mosquitto代理者和客戶端

1，介紹

mqtt是個網絡協議，mosquitto是一個開源的mqtt broker，當然了它也有它的客戶端，命令行和API都有，但是一般用它的命令行，而客戶端API用paho的，paho是一個開源的mqtt client。很多人把mosquitto叫做服務器，只是爲了好理解而已，事實上broker翻譯過來是代理者。mqtt的工作原理，就是發佈的客戶端把話題和消息給broker，broker再轉發給訂閱的客戶端。訂閱客戶端和發佈客戶端可以調換身份，而且不限制客戶端的數量。

mosquitto 源碼鏈接：https://github.com/eclipse/mosquitto

paho 源碼鏈接 ： https://github.com/eclipse/paho.mqtt.c

2，安裝代理者和客戶端 

我這裏是debian10.

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

3， 啓動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.

開始都是在mosquitto.conf裏面配置的（現在添加不生效），現在是在conf.d/下的xxx.conf文件裏面配置，上面的README就是說，在conf.d目錄下的所有的.conf文件都會被broker加載到配置文件中去，如下，我配置了bind_address：

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

5，測試

訂閱：

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

發佈：

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:~$

這裏的測試有Error是因爲，開始broker綁定的ip是localhost，現在改成了192.168.1.107.