分为以下部分：
1：接线并使用AT指令验证连接
2：使用软串口
3：搭建/配置/测试MQTT服务端
4：在Arduino实现MQTT的PUB客户端
5：总结

接线并使用AT指令验证连接

需要各种线+10k电阻*1
ESP8266的3V3/VCC 接到 3.3V
ESP8266的EN 串联一个10k电阻 接到3.3V
ESP8266的RX 接到 Arduino的RX0
ESP8266的TX 接到 Arduino的TX1
ESP8266的GND 接地

//验证程序
const int tx = 1;
const int rx = 0;
void setup() { 
  pinMode(rx,INPUT_PULLUP);
  pinMode(tx,INPUT_PULLUP);
}
void loop() { 
}

将Serial Monitor调整为Both NL&CR，115200 baud
输入AT，ESP8266蓝色灯光闪烁，返回OK
输入AT+GMR，返回版本等信息
如下：

至此，可以验证连接成功。

一些其他常用的AT命令：
AT+RST 重置wifi模块
AT+CWLAP 扫AP
AT+CWJAP=”SSID”,”PASSWORD” 连接到AP
AT+CWJAP=””,”” 与所有访问点断开连接
AT+CIFSR 显示获得的IP和MAC
AT+UART=9600,8,1,0,0 修改波特率等
AT+CWMODE= 设置工作模式，可有Station\AP\Station+AP三种

使用软串口

修改ESP8266的波特率为9600
假设将2，3分别作为RX，TX
则将ESP8266的RX与3（Arduino的TX）相连，反之亦如此
代码：

#include <SoftwareSerial.h>
SoftwareSerial mySerial(2, 3);
void setup() { 
  Serial.begin(9600);
  mySerial.begin(9600);
  mySerial.println("AT+GMR");
}
void loop() { 
  if(wifiSerial.available()) { 
    Serial.write(wifiSerial.read());
  }
  if(Serial.available()){ 
    wifiSerial.write(Serial.read());
  }
}

之后打开Serial Monitor即可看到AT+GMR的执行结果了，也可以使用AT指令查看其他信息。

搭建/配置/测试MQTT服务端

服务器使用Ubuntu+mosquitto

apt-add-repository ppa:mosquitto-dev/mosquitto-ppa
apt-get update
apt-get install mosquitto
cd /etc/mosquitto/conf.d
touch myconfig.conf
vim myconfig.conf
echo allow_anonymous false >> myconfig.conf
echo password_file /etc/mosquitto/pwfile.txt >> myconfig.conf
echo port 1883 >> myconfig.conf
mosquitto_passwd -c /etc/mosquitto/pwfile.txt [username]
service mosquitto start

在云平台调整服务器的安全组，放行出入1883端口的数据
使用python测试服务是否正常：

#sub.py
import paho.mqtt.client as mqtt
def on_connect(client, userdata, flags, rc):
    print("Connect result:" + str(rc))
    client.subscribe("test_topic")
def on_message(client, userdata, msg):
    print(msg.topic+":" +str(msg.payload))
client = mqtt.Client("admin_sub")
client.username_pw_set("[username]","[password]")
client.on_connect = on_connect
client.on_message = on_message
print("Connectting…")
client.connect("[IP]", 1883, 60)
client.loop_forever()

#pub.py
import paho.mqtt.client as mqtt
def on_connect(client, userdata, flags, rc):
    print("Connect result:" + str(rc))
def on_message(client, userdata, msg):
    print(msg.topic + " " + str(msg.payload))
client = mqtt.Client("admin_pub")
client.on_connect = on_connect
client.on_message = on_message
client.connect('[IP]', 1883, 60)
client.publish('test_topic', payload='test_pub_content', qos=0)

可以连接/通讯，如图：

在Arduino实现MQTT的PUB客户端

网上能找到的资料都需要烧写ESP8266，因为怕写坏自己唯一的板子，所以实现了软串口+TCP协议的MQTT客户端，站在别人肩膀上先实现Pub功能。没有做安全保护0.0。
最终实现效果及代码：

#include <SoftwareSerial.h>

SoftwareSerial wifiSerial(2, 3);
bool on;

void setup()
{ 
  Serial.begin(9600);
  wifiSerial.begin(9600);
  while (!Serial);
  while (!wifiSerial);

  wifiSerial.println("AT+RST");
  on=false;
  while(!on){ 
    if(wifiSerial.find("OK")){ 
      Serial.println("ESP8266 Resetting");
      on = true;
    }
  }
  on = false;
  delay(5000);  //Give enough time for ESP8266's reset 
  
  connect_wifi();
  delay(1000);
  pub_msg();
}
 
void loop() { 
  if(wifiSerial.available())
    Serial.write(wifiSerial.read());
  if(Serial.available()){ 
    wifiSerial.write(Serial.read());
  }
}

void connect_wifi(){ 
  wifiSerial.println("AT+RST");
  while(!on){ 
    if(wifiSerial.find("ready")){ 
      delay(1000);
      on = true;
    }
  }
  clear_serial();
  on=false;
  
  wifiSerial.println("AT+CWMODE=1");
  wifiSerial.println("\"hausahan\",\"[password]\"");
  delay(3000);
  if(wifiSerial.find("OK")){ 
      Serial.println("WIFI Connected!");
      delay(1000);
      clear_serial();
      tcp_connect();
  }
}

void tcp_connect(){ 
    wifiSerial.println("AT+CIPSTART=\"TCP\",\"114.116.239.164\",1883");
    delay(1000);
    while(!on){ 
        on = true;
        if(wifiSerial.find("OK")){ 
           Serial.println("TCP Connected!");
        }
    }
    mqtt_connect();
}

void mqtt_connect(){ 
   u8 mqttMessage[128]={ 0};
   u8 packetLen;
   u8 baseIndex = 0;
   u8 clientIdLen = strlen("arduino_pub");
   u8 UserNameLen = strlen("hausa");
   u8 passwordLen = strlen("[password]");
   packetLen = 16 + clientIdLen + UserNameLen + passwordLen;
   mqttMessage[0] = 16;
   mqttMessage[1] = packetLen - 2;
   mqttMessage[3] = 4;       // Protocol Name Length LSB 
   mqttMessage[4] = 77;      // ASCII Code for M 
   mqttMessage[5] = 81;      // ASCII Code for Q 
   mqttMessage[6] = 84;      // ASCII Code for T 
   mqttMessage[7] = 84;      // ASCII Code for T 
   mqttMessage[8] = 4;       // MQTT Protocol version = 4 
   mqttMessage[9] = 130;     // conn flags 
   mqttMessage[10] = 0;      // Keep-alive Time Length MSB 
   mqttMessage[11] = 60;     // Keep-alive Time Length LSB 
   mqttMessage[12] = (0xff00 & clientIdLen)>>8;// Client ID length MSB
   mqttMessage[13] = 0xff & clientIdLen; 
   for(u8 i = 0; i < clientIdLen; i++){ 
        mqttMessage[14 + i] = *((u8*)"arduino_pub" + i);    
   }
   
   baseIndex = 14 + clientIdLen;
   mqttMessage[baseIndex++] = (0xff00 & UserNameLen)>>8; //username length MSB 
   mqttMessage[baseIndex++] = 0xff & UserNameLen;        //username length LSB 
   for(u8 i = 0; i < UserNameLen ; i++){ 
      mqttMessage[baseIndex + i] = *((u8*)"hausa" + i);    
   }

   baseIndex = 14 + clientIdLen + UserNameLen;
   mqttMessage[baseIndex++] = (0xff00 & UserNameLen)>>8; //password length MSB 
   mqttMessage[baseIndex++] = 0xff & UserNameLen;        //password length LSB 
   for(u8 i = 0; i < UserNameLen ; i++){ 
      mqttMessage[baseIndex + i] = *((u8*)"[password]" + i);    
   }
   
   send_tcp_package(mqttMessage, packetLen);
}

void pub_msg(){ 
  u8 mqttMessage[100]={ 0};
  u16 i,index=0;  
  u16 topicLen = strlen("test_topic");    
  u16 messageLen = strlen("arduino_say_hi");  

  mqttMessage[index++] = 48;
  mqttMessage[index++] = 2 + topicLen + messageLen;
  mqttMessage[index++] = (0xff00 & topicLen)>>8;
  mqttMessage[index++] = 0xff & topicLen;
  for(i = 0; i < topicLen; i++){ 
    mqttMessage[index + i] = *((u8 *)"test_topic" + i);
  }
  index += topicLen;
  for(i = 0; i < messageLen; i++){ 
    mqttMessage[index + i] = *((u8*)"arduino_say_hi" + i);
  }

  send_tcp_package(mqttMessage, 4 + topicLen + messageLen);
 
}

void send_tcp_package(u8 *data,u16 len){ 
  clear_serial();
  wifiSerial.print("AT+CIPSEND=");
  wifiSerial.println(len);
  delay(500);
  if(wifiSerial.find(">")){ 
    for(u16 i=0; i<len; i++)
      wifiSerial.write(data[i]);
    wifiSerial.println();
    delay(500);
  }
}

void clear_serial(){ 
  while(wifiSerial.read()>= 0);
  while(Serial.read()>= 0);
}

总结

还是有很多让人疑惑的问题的，比如：
ESP8266很多指令执行后必须等几秒才能进行下一步操作。
也有收获：
每次编程后使用AT+RST进行重置并在烧写完成后复位Arduino能解决很多奇怪的问题。
更理解通信协议、协议栈、wireshark的使用、、、等知识了
下一步：
考虑多买几块8266，学习直接使用8266的方法，因为看起来好像很方便，并实现一个远程控制LED的Deeeeeemo。再然后怎么不做一套智能家居？

参考文章
https://blog.csdn.net/Fredric_2014/article/details/89602457
https://blog.csdn.net/anxianfeng55555/article/details/80908795
也欢迎各位来窝的小窝看窝:www.hausahan.cn/iot/