# 3.14 DISCONNECT –断开连接

## 3.14 DISCONNECT –断开连接

DISCONNECT报文是客户端发给服务端的最后一个控制报文。表示客户端正常断开连接。

### 3.14.1 固定报头

#### 图例 3.35 – DISCONNECT报文固定报头

| **Bit** | **7**           | **6** | **5** | **4** | **3** | **2** | **1** | **0** |
| ------- | --------------- | ----- | ----- | ----- | ----- | ----- | ----- | ----- |
| byte 1  | MQTT控制报文类型 (14) | 保留位   |       |       |       |       |       |       |
|         | 1               | 1     | 1     | 0     | 0     | 0     | 0     | 0     |
| byte 2  | 剩余长度 (0)        |       |       |       |       |       |       |       |
|         | 0               | 0     | 0     | 0     | 0     | 0     | 0     | 0     |

服务端**必须**验证所有的保留位都被设置为0，如果它们不为0**必须**断开连接 \[MQTT-3.14.1-1]。

### 3.14.2 可变报头

DISCONNECT报文没有可变报头。

### 3.14.3 有效载荷

DISCONNECT报文没有有效载荷。

### 3.14.4 响应

客户端发送DISCONNECT报文之后：

* **必须**关闭网络连接 \[MQTT-3.14.4-1]。
* **不能**通过那个网络连接再发送任何控制报文 \[MQTT-3.14.4-2]。

服务端在收到DISCONNECT报文时：

* **必须**丢弃任何与当前连接关联的未发布的遗嘱消息，具体描述见 3.1.2.5节 \[MQTT-3.14.4-3]。
* **应该**关闭网络连接，如果客户端 还没有这么做。

## 第三章目录 MQTT控制报文

* [3.0 Contents – MQTT控制报文](/mqtt/03-controlpackets.md)
* [3.1 CONNECT – 连接服务端](/mqtt/03-controlpackets/0301-connect.md)
* [3.2 CONNACK – 确认连接请求](/mqtt/03-controlpackets/0302-connack.md)
* [3.3 PUBLISH – 发布消息](/mqtt/03-controlpackets/0303-publish.md)
* [3.4 PUBACK –发布确认](/mqtt/03-controlpackets/0304-puback.md)
* [3.5 PUBREC – 发布收到（QoS 2，第一步）](/mqtt/03-controlpackets/0305-pubrec.md)
* [3.6 PUBREL – 发布释放（QoS 2，第二步）](/mqtt/03-controlpackets/0306-pubrel.md)
* [3.7 PUBCOMP – 发布完成（QoS 2，第三步）](/mqtt/03-controlpackets/0307-pubcomp.md)
* [3.8 SUBSCRIBE - 订阅主题](/mqtt/03-controlpackets/0308-subscribe.md)
* [3.9 SUBACK – 订阅确认](/mqtt/03-controlpackets/0309-suback.md)
* [3.10 UNSUBSCRIBE –取消订阅](/mqtt/03-controlpackets/0310-unsubscribe.md)
* [3.11 UNSUBACK – 取消订阅确认](/mqtt/03-controlpackets/0311-unsuback.md)
* [3.12 PINGREQ – 心跳请求](/mqtt/03-controlpackets/0312-pingreq.md)
* [3.13 PINGRESP – 心跳响应](/mqtt/03-controlpackets/0313-pingresp.md)
* [3.14 DISCONNECT –断开连接](/mqtt/03-controlpackets/0314-disconnect.md)

### 第三章目录 MQTT控制报文

* [3.0 Contents – MQTT控制报文](/mqtt/03-controlpackets.md)
* [3.1 CONNECT – 连接服务端](/mqtt/03-controlpackets/0301-connect.md)
* [3.2 CONNACK – 确认连接请求](/mqtt/03-controlpackets/0302-connack.md)
* [3.3 PUBLISH – 发布消息](/mqtt/03-controlpackets/0303-publish.md)
* [3.4 PUBACK –发布确认](/mqtt/03-controlpackets/0304-puback.md)
* [3.5 PUBREC – 发布收到（QoS 2，第一步）](/mqtt/03-controlpackets/0305-pubrec.md)
* [3.6 PUBREL – 发布释放（QoS 2，第二步）](/mqtt/03-controlpackets/0306-pubrel.md)
* [3.7 PUBCOMP – 发布完成（QoS 2，第三步）](/mqtt/03-controlpackets/0307-pubcomp.md)
* [3.8 SUBSCRIBE - 订阅主题](/mqtt/03-controlpackets/0308-subscribe.md)
* [3.9 SUBACK – 订阅确认](/mqtt/03-controlpackets/0309-suback.md)
* [3.10 UNSUBSCRIBE –取消订阅](/mqtt/03-controlpackets/0310-unsubscribe.md)
* [3.11 UNSUBACK – 取消订阅确认](/mqtt/03-controlpackets/0311-unsuback.md)
* [3.12 PINGREQ – 心跳请求](/mqtt/03-controlpackets/0312-pingreq.md)
* [3.13 PINGRESP – 心跳响应](/mqtt/03-controlpackets/0313-pingresp.md)
* [3.14 DISCONNECT –断开连接](/mqtt/03-controlpackets/0314-disconnect.md)

### 项目主页

* [MQTT协议中文版](https://github.com/mcxiaoke/mqtt)


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