PHP实现对接MQTT协议

一：什么是MQTT协议

MQTT（Message Queuing Telemetry Transport，消息队列遥测传输）是一个轻量级、发布‑订阅 (Publish‑Subscribe) 模式的即时通讯协议，基于 TCP/IP。专门为带宽有限、设备算力低、网络不稳定的物联网设备设计。

二：MQTT核心模型

MQTT一共有三种角色

发布者 (Publisher)：发送消息的设备 / 程序（传感器、单片机、后端服务）
Broker（消息服务器 / 代理）：中转站，接收消息，转发给订阅者 - 常见 Broker：Mosquitto、EMQX、VerneMQ、RabbitMQ (MQTT 插件)
订阅者 (Subscriber)：接收消息的设备 / 程序（APP、后端、大屏、其他物联网设备）

三：MQTT协议优缺点

1. 优点

数据包极小，头部最小仅 2 字节，流量消耗低，适合单片机、4G / 窄带物联网
异步解耦，设备不需要长轮询
支持断线重连、遗嘱、QoS，适配不稳定网络
跨平台：PHP、Java、Python、小程序、单片机都有客户端库

2. 缺点

不适合海量大文件传输，只适合短消息、指令、状态
Broker 是单点，需要做集群高可用
默认无消息持久化，掉线没收到的消息会丢失（需开启会话持久化 clean‑session=false）

四：使用mosquitto实现MQTT的发布与订阅

1. 安装mosquitto

Ubuntu/Debian安装

复制代码

# 更新源
sudo apt update

# 安装 mosquitto 服务端 + 客户端工具
sudo apt install mosquitto mosquitto-clients -y

CentOS 7/Rocky/AlmaLinux/RHEL安装

复制代码

sudo yum install epel-release -y
sudo yum install mosquitto mosquitto-clients -y

启动mosquitto

复制代码

sudo systemctl start mosquitto
sudo systemctl enable mosquitto
systemctl status mosquitto

2. mosquitto配置（看情况配置）

配置文件路径

复制代码

/etc/mosquitto/mosquitto.conf
/etc/mosquitto/conf.d/     # 推荐把自定义配置放这里新建文件

创建MQTT账户密码

复制代码

# 创建密码文件
sudo mosquitto_passwd -c /etc/mosquitto/passwd mqttuser

会提示输入两次密码。

再新建 /etc/mosquitto/conf.d/auth.conf

复制代码

listener 1883
allow_anonymous false
password_file /etc/mosquitto/passwd

重启服务

复制代码

sudo systemctl restart mosquitto

3. 发布消息

复制代码

mosquitto_pub -h 【IP】 -p 【端口】 -u 【用户名】 -P 【密码】 -t "【主题 Topic】" -m "【发布的消息】"

4. 订阅消息

复制代码

 mosquitto_sub -h 【IP】 -p 【端口号】 -u 【用户名】 -P 【密码】 -t "【主题 Topic】"

五：PHP对接MQTT协议示例

发布消息

/**
- MQTT 消息发布
- @param string $top MQTT 主题
- @param array $message 发布消息体
- @return mixed
  */
  public function release( $topic,$ message)
  {
  $message = is_array($ message) ? json_encode( $message, JSON_UNESCAPED_UNICODE) :$ message;
  
  $host = '127.0.0.1';//IP
  
  $port = '14001';//端口
  
  $username = 'xxx';//用户名
  
  $password = 'xxx';//密码
  
  $config = [ 'host' =>$ host,
  'port' => $port, 'username' =>$ username,
  'password' => $password, 'topic' =>$ topic,
  'message' => $message,
  ];
  
  try {
  $this->publishMqttMessage($ config);
  复制代码
```
 return true;
```
  } catch (\Throwable $e) {
  return false;
  }
  }
/**
- 发布 MQTT 消息
- @param array $config
- @throws \RuntimeException
  */
  protected function publishMqttMessage(array $config) {$ address = sprintf('tcp://%s:%d', $config['host'],$ config['port']);
  $socket = @stream_socket_client($ address, $errno,$ errstr, 5, STREAM_CLIENT_CONNECT);
  if ( $socket === false) { throw new \RuntimeException("connect {$ address} failed: [{ $errno}] {$ errstr}");
  }
  
  stream_set_timeout($socket, 5);
  
  try {
  $this->writeMqttPacket($ socket, $this->buildMqttConnectPacket( 'platform_' . uniqid(),$ config['username'],
  $config['password'],
  ));
  复制代码
```
 $connack = $this->readMqttPacket($socket);
 $this->assertMqttConnack($connack);

 $this->writeMqttPacket($socket, $this->buildMqttPublishPacket($config['topic'], $config['message']));
 $this->writeMqttPacket($socket, chr(0xE0) . chr(0x00));
```
  } finally {
  fclose($socket);
  }
  }
/**
- CONNACK: payload[0]=session present, payload[1]=return code (0=accepted)
- @param array $connack
- @throws \RuntimeException
  */
  protected function assertMqttConnack(array $connack)
  {
  
  if ($connack['type'] !== 2) {
  throw new \RuntimeException('invalid CONNACK packet');
  }
  
  $returnCode =$ this->mqttPayloadByte( $connack['payload'], 1, 1); if ($ returnCode !== 0) {
  throw new \RuntimeException('MQTT broker rejected connection, code ' . $returnCode);
  }
  }
/**
- @param string $payload
- @param int $offset
- @param int $default
- @return int
  */
  protected function mqttPayloadByte( $payload,$ offset, $default = 0) { if (!is_string($ payload) || !isset( $payload[$ offset])) {
  return $default;
  }
  
  return ord( $payload[$ offset]);
  }
/**
- @param string $string
- @return string
  */
  protected function encodeMqttString( $string) { return pack('n', strlen($ string)) . $string;
  }
/**
- @param string $clientId
- @param string $username
- @param string $password
- @return string
  */
  protected function buildMqttConnectPacket( $clientId,$ username, $password) {$ variableHeader = $this->encodeMqttString('MQTT');$ variableHeader .= chr(4);
  $variableHeader .= chr(0xC2);$ variableHeader .= pack('n', 60);
  
  $payload =$ this->encodeMqttString( $clientId);$ payload .= $this->encodeMqttString($ username);
  $payload .=$ this->encodeMqttString($password);
  
  $body =$ variableHeader . $payload;
  
  return chr(0x10) . $this->encodeMqttRemainingLength(strlen($ body)) . $body;
  }
/**
- @param resource $socket
- @param string $packet */ protected function writeMqttPacket($ socket, $packet) {$ written = fwrite( $socket,$ packet);
  if ( $written === false ||$ written !== strlen($packet)) {
  throw new \RuntimeException('failed to write MQTT packet');
  }
  }
  /**
- @param resource $socket
- @return array{type:int,payload:string}
  */
  protected function readMqttPacket( $socket) {$ fixedHeader = fread( $socket, 1); if ($ fixedHeader === false || $fixedHeader === '') {
  throw new \RuntimeException('failed to read MQTT packet header');
  }
  
  $remainingLength =$ this->decodeMqttRemainingLength( $socket);$ payload = '';
  if ( $remainingLength > 0) {$ payload = fread( $socket,$ remainingLength);
  if ( $payload === false || strlen($ payload) !== $remainingLength) {
  throw new \RuntimeException('failed to read MQTT packet payload');
  }
  }
  
  return [
  'type' => ord( $fixedHeader) >> 4, 'flags' => ord($ fixedHeader) & 0x0F,
  'payload' => $payload,
  ];
  }
  /**
- @param resource $socket
- @return int
  */
  protected function decodeMqttRemainingLength( $socket) {$ multiplier = 1;
  $value = 0;
  
  do {
  $byte = fread($ socket, 1);
  if ( $byte === false ||$ byte === '') {
  throw new \RuntimeException('failed to decode MQTT remaining length');
  }
  复制代码
```
 $digit = ord($byte);
 $value += ($digit & 127) * $multiplier;
 $multiplier *= 128;
 $hasMore = ($digit & 128) !== 0;
```
  } while ($hasMore);
  
  return $value;
  }
/**
- @param int $length
- @return string
  */
  protected function encodeMqttRemainingLength( $length) {$ encoded = '';
  do {
  $digit =$ length % 128;
  $length = intdiv($ length, 128);
  if ( $length > 0) {$ digit |= 0x80;
  }
  $encoded .= chr($ digit);
  } while ($length > 0);
  
  return $encoded;
  }
/**
- @param string $topic
- @param string $message
- @return string
  */
  protected function buildMqttPublishPacket( $topic,$ message)
  {
  $body =$ this->encodeMqttString( $topic) .$ message;
  
  return chr(0x30) . $this->encodeMqttRemainingLength(strlen($ body)) . $body;
  }
订阅消息

/**
- MQTT 订阅监听
- @param string $topic MQTT 主题
- @param int $timeout 监听超时秒数，0 表示持续监听直到 Ctrl+C */ public function subscribe($ topic, $timeout = 0) {$ host = '127.0.0.1';//IP
  
  $port = '14001';//端口
  
  $username = 'xxx';//用户名
  
  $password = 'xxx';//密码
  
  $config = [ 'host' =>$ host,
  'port' => $port, 'username' =>$ username,
  'password' => $password, 'topic' =>$ topic,
  'timeout' => (int) $timeout,
  ];
  
  try {
  $this->subscribeMqttMessage($ config);
  复制代码
```
 return true;
```
  } catch (\Throwable $e) {
  return false;
  }
  }
/**
- 订阅 MQTT 主题并持续接收消息
- @param array $config
- @throws \RuntimeException
  */
  protected function subscribeMqttMessage(array $config) {$ address = sprintf('tcp://%s:%d', $config['host'],$ config['port']);
  $socket = @stream_socket_client($ address, $errno,$ errstr, 5, STREAM_CLIENT_CONNECT);
  if ( $socket === false) { throw new \RuntimeException("connect {$ address} failed: [{ $errno}] {$ errstr}");
  }
  
  stream_set_blocking($socket, true);
  
  if ( $config['timeout'] > 0) { stream_set_timeout($ socket, $config['timeout']);
  }
  
  try {
  $this->writeMqttPacket($ socket, $this->buildMqttConnectPacket( 'platform_sub_' . uniqid(),$ config['username'],
  $config['password'],
  ));
  复制代码
```
 $connack = $this->readMqttPacket($socket);
 $this->assertMqttConnack($connack);

 $this->writeMqttPacket($socket, $this->buildMqttSubscribePacket($config['topic']));
 $suback = $this->readMqttPacket($socket);
 $this->assertMqttSuback($suback);

 while (!feof($socket)) {
     if ($config['timeout'] > 0) {
         $read = [$socket];
         $ready = stream_select($read, $write, $except, $config['timeout']);
         if ($ready === 0) {
             break;
         }
         if ($ready === false) {
             throw new \RuntimeException('failed to wait for MQTT message');
         }
     }

     $packet = $this->readMqttPacket($socket);

     if ($packet['type'] === 3) {
         $publish = $this->parseMqttPublishPacket($packet['payload'], $packet['flags']);

         $data = $publish['message'];//订阅消息
         //TODO 业务代码操作

         continue;
     }

     if ($packet['type'] === 13) {
         $this->writeMqttPacket($socket, chr(0xD0) . chr(0x00));
     }
 }
```
  } finally {
  @fwrite( $socket, chr(0xE0) . chr(0x00)); fclose($ socket);
  }
  }
/**
- @param string $payload
- @param int $flags
- @return array{topic:string,message:string}
  */
  protected function parseMqttPublishPacket( $payload,$ flags)
  {
  $qos = ($ flags >> 1) & 0x03;
  $offset = 0;$ topicLength = unpack('n', substr( $payload,$ offset, 2))[1];
  $offset += 2;$ topic = substr( $payload,$ offset, $topicLength);$ offset += $topicLength;
  
  if ( $qos > 0) {$ offset += 2;
  }
  
  return [
  'topic' => $topic, 'message' => substr($ payload, $offset),
  ];
  }
/**
- SUBACK: payload[0..1]=packet id, payload[2]=granted QoS (0x80=failure)
- @param array $suback
- @throws \RuntimeException
  */
  protected function assertMqttSuback(array $suback) { if ($ suback['type'] !== 9) {
  throw new \RuntimeException('invalid SUBACK packet');
  }
  
  $returnCode =$ this->mqttPayloadByte( $suback['payload'], 2, 0x80); if ($ returnCode === 0x80) {
  throw new \RuntimeException('MQTT broker rejected subscription');
  }
  }
/**
- @param string $payload
- @param int $offset
- @param int $default
- @return int
  */
  protected function mqttPayloadByte( $payload,$ offset, $default = 0) { if (!is_string($ payload) || !isset( $payload[$ offset])) {
  return $default;
  }
  
  return ord( $payload[$ offset]);
  }
/**
- @param string $topic
- @param int $packetId
- @param int $qos
- @return string
  */
  protected function buildMqttSubscribePacket( $topic,$ packetId = 1, $qos = 0) {$ body = pack('n', $packetId) .$ this->encodeMqttString( $topic) . chr($ qos);
  
  return chr(0x82) . $this->encodeMqttRemainingLength(strlen($ body)) . $body;
  }
/**
- @param string $string
- @return string
  */
  protected function encodeMqttString( $string) { return pack('n', strlen($ string)) . $string;
  }
/**
- @param int $length
- @return string
  */
  protected function encodeMqttRemainingLength( $length) {$ encoded = '';
  do {
  $digit =$ length % 128;
  $length = intdiv($ length, 128);
  if ( $length > 0) {$ digit |= 0x80;
  }
  $encoded .= chr($ digit);
  } while ($length > 0);
  
  return $encoded;
  }
/**
- @param resource $socket
- @param string $packet */ protected function writeMqttPacket($ socket, $packet) {$ written = fwrite( $socket,$ packet);
  if ( $written === false ||$ written !== strlen($packet)) {
  throw new \RuntimeException('failed to write MQTT packet');
  }
  }
  /**
- @param string $clientId
- @param string $username
- @param string $password
- @return string
  */
  protected function buildMqttConnectPacket( $clientId,$ username, $password) {$ variableHeader = $this->encodeMqttString('MQTT');$ variableHeader .= chr(4);
  $variableHeader .= chr(0xC2);$ variableHeader .= pack('n', 60);
  
  $payload =$ this->encodeMqttString( $clientId);$ payload .= $this->encodeMqttString($ username);
  $payload .=$ this->encodeMqttString($password);
  
  $body =$ variableHeader . $payload;
  
  return chr(0x10) . $this->encodeMqttRemainingLength(strlen($ body)) . $body;
  }
/**
- @param resource $socket
- @return array{type:int,payload:string}
  */
  protected function readMqttPacket( $socket) {$ fixedHeader = fread( $socket, 1); if ($ fixedHeader === false || $fixedHeader === '') {
  throw new \RuntimeException('failed to read MQTT packet header');
  }
  
  $remainingLength =$ this->decodeMqttRemainingLength( $socket);$ payload = '';
  if ( $remainingLength > 0) {$ payload = fread( $socket,$ remainingLength);
  if ( $payload === false || strlen($ payload) !== $remainingLength) {
  throw new \RuntimeException('failed to read MQTT packet payload');
  }
  }
  
  return [
  'type' => ord( $fixedHeader) >> 4, 'flags' => ord($ fixedHeader) & 0x0F,
  'payload' => $payload,
  ];
  }
/**
- @param resource $socket
- @return int
  */
  protected function decodeMqttRemainingLength( $socket) {$ multiplier = 1;
  $value = 0;
  
  do {
  $byte = fread($ socket, 1);
  if ( $byte === false ||$ byte === '') {
  throw new \RuntimeException('failed to decode MQTT remaining length');
  }
  复制代码
```
 $digit = ord($byte);
 $value += ($digit & 127) * $multiplier;
 $multiplier *= 128;
 $hasMore = ($digit & 128) !== 0;
```
  } while ($hasMore);
  
  return $value;
  }
/**
- CONNACK: payload[0]=session present, payload[1]=return code (0=accepted)
- @param array $connack
- @throws \RuntimeException
  */
  protected function assertMqttConnack(array $connack)
  {
  
  if ($connack['type'] !== 2) {
  throw new \RuntimeException('invalid CONNACK packet');
  }
  
  $returnCode =$ this->mqttPayloadByte( $connack['payload'], 1, 1); if ($ returnCode !== 0) {
  throw new \RuntimeException('MQTT broker rejected connection, code ' . $returnCode);
  }
  }