0 前期教程
1 前言
前面两篇教程主要是使用Mosquitto这个开源软件在虚拟机搭建MQTT服务器，但是关于客户端部分一直是用MQTTX这个软件实现的，那能不能用其他的来实现呢？
2 Python：Paho.mqtt
如果想用python写一个客户端连接到服务器并进行订阅和发布，开源使用Eclipse的Paho这个库，安装很简单：
pip install paho-mqtt
这个库的使用也很简单，这里只给一个示例代码：
import paho.mqtt.client as mqtt
user = ''
passwd = ''
broker = ''
port = 1883
def on_connect(client, userdata, flags, rc):
print("Connected with result code: " + str(rc))
print(client.is_connected()) #判断服务器是否连接成功
def on_message(client, userdata, msg):
print(msg.topic + " " + str(msg.payload))
def subscribe():
# 如果是一般的MQTT协议
client = mqtt.Client()
# 如果是websocket协议
# client = mqtt.Client(transport="websockets")
#设置用户名和密码（可选）
# client.username_pw_set(user, passwd)
client.on_connect = on_connect
client.on_message = on_message
# 如果要设置TLS, 需要加上
# client.tls_set(ca_certs='C:\\Users\\Admin\\Desktop\\ca.crt',cert_reqs=ssl.CERT_NONE) #因为是自签证书，所以要加上后面那个参数和下一行代码
# client.tls_insecure_set(True)
#连接 IP port keepalive
client.connect(broker, port, 600)
#订阅的 topic
client.subscribe('test', qos=0)
client.loop_forever()
def publish():
client = mqtt.Client()
#设置用户名和密码
client.username_pw_set("user1", "password")
client.on_connect = on_connect
client.on_message = on_message
#连接 IP port keepalive
client.connect(broker, port, 600)
#发布 topic 内容
client.publish('test', payload='have a seventh test', qos=0)
client.publish('test', payload='have a eighth test', qos=0)
# publish()
subscribe()
设置自签证书参考：link
3 ESP32等嵌入式设备
对于ESP32这种嵌入式设备，好在也有第三方的库可以调用。这里使用的是PubSubClient这个库。这个库的使用可以参考它的官网。
下面也给出一个示例代码。
#include <WiFi.h>
#include <PubSubClient.h>
#include <WiFiClientSecure.h>
const char *ssid = "";
const char *password = "";
const char *mqtt_server = "";
const char *clientid = "";
const char *mqtt_user = "";
const char *mqtt_password = "";
const char *topic = "";
const int mqtt_port = 1883;
const char *websockets_server_host = "wss://j81e5815.ala.cn-hangzhou.emqxsl.cn"; // Enter server adress
const uint16_t websockets_server_port = 8084; // Enter server port
const char *MQTTCLOUD_CA = "-----BEGIN CERTIFICATE-----\n"
"-----END CERTIFICATE-----"; //这个是证书的内容，因为它本质也是文本文件
WiFiClient espClient; //这个用于一般的MQTT协议
WiFiClientSecure wifi; //这个用于带有TLS的MQTT协议
// PubSubClient client(espClient);
PubSubClient client(wifi);
void reconnect()
{
while (!client.connected())
{
Serial.println("Connecting to MQTT Server...");
if (client.connect("ESP32Client", mqtt_user, mqtt_password))
{
// Replace with your MQTT username and password
Serial.println("Connected to MQTT Server!");
client.subscribe("test_topic"); // Subscribe to topic
}
else
{
Serial.println("MQTT Connection failed, retrying...");
delay(5000);
}
}
}
void callback(char *topic, byte *message, unsigned int length)
{
Serial.print("Message received on topic: ");
Serial.println(topic);
Serial.print("Message content: ");
for (int i = 0; i < length; i++)
{
Serial.print((char)message[i]);
}
Serial.println();
}
void setup()
{
Serial.begin(115200);
WiFi.begin(ssid, password);
while (WiFi.status() != WL_CONNECTED)
{
delay(1000);
Serial.println("Connecting to WiFi...");
}
Serial.println("Connected to WiFi! The IP Address is :");
Serial.println(WiFi.localIP());
wifi.setCACert(MQTTCLOUD_CA); // 添加CA证书
client.setClient(wifi);
client.setServer(mqtt_server, mqtt_port); // Replace with your MQTT server IP and port
client.setCallback(callback);
while (!client.connected())
{
Serial.println("Connecting to MQTT Server...");
if (client.connect(clientid, mqtt_user, mqtt_password))
{
Serial.println("Connected to MQTT Server!");
client.subscribe(topic); // Subscribe to topic
}
else
{
Serial.println("MQTT Connection failed, retrying...");
delay(5000);
}
}
}
void loop()
{
if (!client.connected())
{
reconnect();
}
client.loop();
}