void MQTT_Connect(char *clientid, char *username, char *passward) { char data[256] = {0}; /* 报文缓存数组 */ int len = 0; /* 报文长度计数变量 */ int remaining_length = 0; /* 剩余长度(可变报头 + 有效载荷) */ char flags = 0; /* 连接标志 */ int clientid_length = strlen(clientid); int will_topic_length = strlen(WILL_TOPIC); int will_message_length = strlen(WILL_MESSAGE); int username_length = strlen(username); int passward_length = strlen(passward); /*------------------ 连接标志配置 -----------------------*/ /* bit1 是否清除会话 */ if (CLEAN_SESSION) { flags |= 0x02; } /* bit2 是否使用遗嘱消息 */ if (WILL_FLAG) { flags |= 0x04; /* bit3、bit4 遗嘱QoS等级, 默认 QoS0 */ if (WILL_QOS == 1) { /* QoS1 */ flags |= 0x08; } if (WILL_QOS == 2) { /* QoS2 */ flags |= 0x10; } /* bit5 是否保留本次会话 */ if (WILL_RETAIN) { flags |= 0x20; } } /* bit6、bit7 是否使用账号、密码 */ if (USER_NAME_FLAG && PASS_WORD_FLAG) { flags |= 0xC0; /* 0x80 | 0x40 */ } /*------------------ 连接标志配置 END -------------------*/ /* 剩余长度 = 可变报头 + 负载的数据 */ remaining_length = 10 + (2 + clientid_length); if (WILL_FLAG) { remaining_length += (2 + will_topic_length) + (2 + will_message_length); } if (USER_NAME_FLAG) { remaining_length += (2 + username_length) + (2 + passward_length); } /* 1. Connect固定报头(Fixed header) */ data[len++] = 0x10; /* MQTT Message Type CONNECT */ /* 1.2 剩余长度编码 */ do { char encodedbyte = remaining_length % 128; remaining_length = remaining_length / 128; if (remaining_length > 0) { encodedbyte |= 128; } data[len++] = encodedbyte; } while (remaining_length > 0); /* 2. 可变报头(Variable header) */ data[len++] = 0; /* Protocol Name MSB */ data[len++] = 4; /* Protocol Name LSB */ data[len++] = 'M'; data[len++] = 'Q'; data[len++] = 'T'; data[len++] = 'T'; data[len++] = 4; /* Protocol Level */ data[len++] = flags; /* Connect Flags */ data[len++] = KEEP_ALIVE / 256; /* Keep Alive MSB */ data[len++] = KEEP_ALIVE % 256; /* Keep Alive LSB */ /* 3. 有效载荷(Payload) */ /* 3.1 客户端ID */ data[len++] = clientid_length / 256; data[len++] = clientid_length % 256; memcpy(&data[len], clientid, clientid_length); len += clientid_length; if (WILL_FLAG) { /* 3.2 遗嘱主题 */ data[len++] = will_topic_length / 256; data[len++] = will_topic_length % 256; memcpy(&data[len], WILL_TOPIC, will_topic_length); len += will_topic_length; /* 3.3 遗嘱消息 */ data[len++] = will_message_length / 256; data[len++] = will_message_length % 256; memcpy(&data[len], WILL_MESSAGE, will_message_length); len += will_message_length; } if (USER_NAME_FLAG && PASS_WORD_FLAG) { /* 3.4 用户名 */ data[len++] = username_length / 256; data[len++] = username_length % 256; memcpy(&data[len], username, username_length); len += username_length; /* 3.5 密码 */ data[len++] = passward_length / 256; data[len++] = passward_length % 256; memcpy(&data[len], passward, passward_length); len += passward_length; } Write_MQTT_TxDataBuff(data, len); /* 数据写入发送缓冲区 */ mqtt_debug(data, len, "\r\n* 1、CONNECT - 连接服务端 *: \r\n"); }简化这个函数