| 0 | 0x00 | 成功 (Success) | CONNACK, PUBACK, PUBREC, PUBREL, PUBCOMP, UNSUBACK, AUTH |
| 0 | 0x00 | 准许 QoS 0 (Granted QoS 0) | SUBACK |
| 1 | 0x01 | 准许 QoS 1 (Granted QoS 1) | SUBACK |
| 2 | 0x02 | 准许 QoS 2 (Granted QoS 2) | SUBACK |
| 4 | 0x04 | 以遗嘱消息断开连接 (Disconnect with Will Message) | DISCONNECT |
| 16 | 0x10 | 没有匹配的订阅者 (No matching subscribers) | PUBACK, PUBREC |
| 17 | 0x11 | 没有订阅 (No subscription existed) | UNSUBACK |
| 24 | 0x18 | 继续认证 (Continue authentication) | AUTH |
| 25 | 0x19 | 重新认证 (Re-authenticate) | AUTH |
| 128 | 0x80 | 未指定错误 (Unspecified error) | CONNACK, PUBACK, PUBREC, SUBACK, UNSUBACK, DISCONNECT |
| 129 | 0x81 | 畸形报文 (Malformed Packet) | CONNACK, DISCONNECT |
| 130 | 0x82 | 协议错误 (Protocol Error) | CONNACK, DISCONNECT |
| 131 | 0x83 | 实现特有错误 (Implementation specific error) | CONNACK, PUBACK, PUBREC, SUBACK, UNSUBACK, DISCONNECT |
| 132 | 0x84 | 不支持的协议版本 (Unsupported Protocol Version) | CONNACK |
| 133 | 0x85 | 客户端标识符无效 (Client Identifier not valid) | CONNACK |
| 134 | 0x86 | 错误的用户名和密码 (Bad User Name or Password) | CONNACK |
| 135 | 0x87 | 未授权 (Not authorized) | CONNACK, PUBACK, PUBREC, SUBACK, UNSUBACK, DISCONNECT |
| 136 | 0x88 | 服务器不可用 (Server unavailable) | CONNACK |
| 137 | 0x89 | 服务器繁忙 (Server busy) | CONNACK, DISCONNECT |
| 138 | 0x8A | 禁止访问 (Banned) | CONNACK |
| 139 | 0x8B | 服务器关机中 (Server shutting down) | DISCONNECT |
| 140 | 0x8C | 错误验证方法 (Bad authentication method) | CONNACK, DISCONNECT |
| 141 | 0x8D | 保活超时 (Keep Alive timeout) | DISCONNECT |
| 142 | 0x8E | 会话被接管 (Session taken over) | DISCONNECT |
| 143 | 0x8F | 主题过滤器无效 (Topic Filter invalid) | SUBACK, UNSUBACK, DISCONNECT |
| 144 | 0x90 | 主题名无效 (Topic Name invalid) | CONNACK, PUBACK, PUBREC, DISCONNECT |
| 145 | 0x91 | 报文标识符在使用中 (Packet Identifier in use) | PUBACK, PUBREC, SUBACK, UNSUBACK |
| 146 | 0x92 | 没有发现报文标识符 (Packet Identifier not found) | PUBREL, PUBCOMP |
| 147 | 0x93 | 超出接收最大值 (Receive Maximum exceeded) | DISCONNECT |
| 148 | 0x94 | 主题别名无效 (Topic Alias invalid) | DISCONNECT |
| 149 | 0x95 | 报文太大 (Packet too large) | CONNACK, DISCONNECT |
| 150 | 0x96 | 消息传输速率太高 (Message rate too high) | DISCONNECT |
| 151 | 0x97 | 超出限额 (Quota exceeded) | CONNACK, PUBACK, PUBREC, SUBACK, DISCONNECT |
| 152 | 0x98 | 管理行为 (Administrative action) | DISCONNECT |
| 153 | 0x99 | 有效载荷格式无效 (Payload format invalid) | PUBACK, PUBREC, DISCONNECT |
| 154 | 0x9A | 不支持消息保留 (Retain not supported) | CONNACK, DISCONNECT |
| 155 | 0x9B | 不支持的QoS (QoS not supported) | CONNACK, DISCONNECT |
| 156 | 0x9C | 使用另一台服务器 (Use another server) | CONNACK, DISCONNECT |
| 157 | 0x9D | 服务器被移除 (Server moved) | CONNACK, DISCONNECT |
| 158 | 0x9E | 不支持的共享订阅 (Shared Subscription not supported) | SUBACK, DISCONNECT |
| 159 | 0x9F | 超出连接速率 (Connection rate exceeded) | CONNACK, DISCONNECT |
| 160 | 0xA0 | 最大连接时间 (Maximum connect time) | DISCONNECT |
| 161 | 0xA1 | 不支持的订阅标识符 (Subscription Identifiers not supported) | SUBACK, DISCONNECT |
| 162 | 0xA2 | 不支持的通配符订阅 (Wildcard Subscription not supported) | SUBACK, DISCONNECT |