1，源碼下載：
https://github.com/eclipse/paho.mqtt.c
解壓：
guoyanzhang@debian:~/test$ unzip paho.mqtt.c-master.zip
2，安裝編譯用的庫
guoyanzhang@debian:~/test/paho.mqtt.c-master$ sudo apt-get install build-essential gcc make cmake cmake-gui cmake-curses-gui
guoyanzhang@debian:~/test/paho.mqtt.c-master$ sudo apt-get install fakeroot fakeroot devscripts dh-make lsb-release
guoyanzhang@debian:~/test/paho.mqtt.c-master$ sudo apt-get install libssl-dev
guoyanzhang@debian:~/test/paho.mqtt.c-master$ sudo apt-get install doxygen graphviz
3，編譯
guoyanzhang@debian:~/test/paho.mqtt.c-master$ make
guoyanzhang@debian:~/test/paho.mqtt.c-master$ sudo make install
guoyanzhang@debian:~/test/paho.mqtt.c-master$ make html
4，把頭文件拷貝到自己要用的地方（這步根據自己的需要選擇做）
guoyanzhang@debian:~/test$ cp paho.mqtt.c-master/src/MQTTAsync.h mqtt_h/
guoyanzhang@debian:~/test$ cp paho.mqtt.c-master/src/MQTTClientPersistence.h mqtt_h/
guoyanzhang@debian:~/test$ cp paho.mqtt.c-master/src/MQTTProperties.h mqtt_h/
guoyanzhang@debian:~/test$ cp paho.mqtt.c-master/src/MQTTReasonCodes.h mqtt_h/
guoyanzhang@debian:~/test$ cp paho.mqtt.c-master/src/MQTTSubscribeOpts.h mqtt_h/
5，編譯的時候要用-lpaho-mqtt3a
The Paho C client comprises four shared libraries:
libmqttv3a.so - asynchronous (MQTTAsync)
libmqttv3as.so - asynchronous with SSL (MQTTAsync)
libmqttv3c.so - "classic" / synchronous (MQTTClient)
libmqttv3cs.so - "classic" / synchronous with SSL (MQTTClient)
3a是異步，3as是帶ssl的異步，3c是同步，3cs是帶ssl的同步。
paho是分異步函數和同步函數的，異步函數是非阻塞的，就是把消息發到broker，函數會立即返回，但是消息並未被執行，而是加入一個隊列，等待執行，同步函數是阻塞的，等到消息被執行才返回。異步函數也可以加一些其它的參數變成同步阻塞，總體來說，異步函數包含同步函數。