MQTT协议
//请求连接void mqtt_connect(char *clientid,char *username,char *passwd)
{
uint32_t clientid_len = strlen(clientid);
uint32_t username_len = strlen(username);
uint32_t passwd_len = strlen(passwd);
//用于存储剩余长度 = 可变包头+有效载荷（客户端id+2+用户名+2+密码+2）;
uint32_t remain_len = 10 + (clientid_len+2)+ (username_len+2)+ (passwd_len+2);
//1 对发送缓冲区进行初始化
memset((char *)sendbuf,0,512);
sendcnt = 0;
//2 固定包头
sendbuf = 0x10;//connect
//3 对剩余长度进行编码
do
{
uint8_t encodeByte = remain_len %128;
remain_len = remain_len /128;
if(remain_len >0)
{
encodeByte = encodeByte |128;
}
sendbuf = encodeByte;
}
while(remain_len >0);
//4 可变包头
sendbuf = 0;
sendbuf = 4;
sendbuf = 'M';//协议名称
sendbuf = 'Q';
sendbuf = 'T';
sendbuf = 'T';
sendbuf = 4;//协议版本
sendbuf = 0xc2 ;//连接标志
sendbuf = 0 ;//保持连接
sendbuf = 120 ;//2分钟
//5 有效载荷 客户端id 用户名 密码
sendbuf = BYTE1(clientid_len); //msb
sendbuf = BYTE0(clientid_len); //lsb
memcpy(&sendbuf ,clientid,clientid_len);
sendcnt +=clientid_len;
sendbuf = BYTE1(username_len); //msb
sendbuf = BYTE0(username_len); //lsb
memcpy(&sendbuf ,username,username_len);
sendcnt +=username_len;
sendbuf = BYTE1(passwd_len); //msb
sendbuf = BYTE0(passwd_len); //lsb
memcpy(&sendbuf ,passwd,passwd_len);
sendcnt +=passwd_len;
//6 把connect报文发送出去
Serial_Sendstring(sendbuf,sendcnt);
}//发布消息
void mqtt_publish(char *topic,uint8_t Qos,char *databuf)
{
uint32_t remain_len;
uint32_t topic_len = strlen(topic);
uint32_t databuf_len = strlen(databuf);//有效载荷
//用于存储剩余长度 = 可变包头+有效载荷（客户端id+2+用户名+2+密码+2）;
if(Qos == 0)
{
remain_len = (topic_len+2)+(databuf_len);
}
else
{
remain_len = (topic_len+2)+(databuf_len) + 2;
}
//1 对发送缓冲区进行初始化
memset((char *)sendbuf,0,512);
sendcnt = 0;
//2 固定包头
sendbuf = 0x30;//connect
//3 对剩余长度进行编码
do
{
uint8_t encodeByte = remain_len %128;
remain_len = remain_len /128;
if(remain_len >0)
{
encodeByte = encodeByte |128;
}
sendbuf = encodeByte;
}
while(remain_len >0);
//可变包头
sendbuf = BYTE1(topic_len); //msb
sendbuf = BYTE0(topic_len); //lsb
memcpy(&sendbuf ,topic,topic_len);
sendcnt +=topic_len;
//有效载荷
// sendbuf = BYTE1(databuf_len); //msb
// sendbuf = BYTE0(databuf_len); //lsb
memcpy(&sendbuf ,databuf,databuf_len);
sendcnt +=databuf_len;
//6 把connect报文发送出去
Serial_Sendstring(sendbuf,sendcnt);
}//订阅消息
void mqtt_subscribe(const char *Filter, uint16_t msg_id, uint8_t qos)
{
char data = {0};
int cnt = 0;
uint32_t remain;
// 固定包头
data = 0x82; // 订阅消息类型
// 计算剩余字节长度
uint32_t Filter_len = strlen(Filter);
remain = 2 + Filter_len + 2 + 1; // 消息 ID (2 字节) + 主题长度 (2 字节) + 主题 (Filter_len 字节) + QoS (1 字节)
// 编码剩余字节
do
{
uint8_t encodeByte = remain % 128;
remain = remain / 128;
if (remain > 0)
{
encodeByte |= 128;
}
data = encodeByte;
}
while (remain > 0);
// 可变包头
data = BYTE1(msg_id); // 消息 ID 高字节
data = BYTE0(msg_id); // 消息 ID 低字节
// 有效载荷
data = BYTE1(Filter_len); // 主题长度高字节
data = BYTE0(Filter_len); // 主题长度低字节
memcpy(&data, Filter, Filter_len); // 主题
cnt += Filter_len;
data = qos; // QoS 级别
// 发送构建的 MQTT 消息
Serial_Sendstring(data, cnt);
}//保持心跳请求
void mqtt_keepalive()
{
uint8_t buf = {0xc0,0x00};
}
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