單片機使用C語言實作MQTT協議

單片機使用C語言實作MQTT協議

在單片機使用MQTT協議非常普遍，特別是在物聯網相關領域，在阿里云，華為云等公有云都提供MQTT協議連接物聯網平臺，
本篇介紹如何用C語言實作MQTT的連接

MQTT連接主要有五步驟：
1.　連接云平臺
2.　登錄用戶名密碼等
3.　訂閱主題
4.　發送心跳包
5.　發布主題

1.　連接云平臺跟其他網站一樣，只要有服務器地址和埠號就行，在這里我使用了以太網口去連接
代碼如下：

u16 AnalyTarIp(u8 *TarIp,u16 port,u8 i)
{
	static u8 dnsSel = 0;
	u16 stateStamp;
	uip_ipaddr_t ipaddr;
	u8 ip[4];
			
	g_mconn[i].flag = 0;
	stateStamp = GetSecCnt();
			//á??ó·t???÷
	g_mconn[i].port = port;		//埠
			//IP還是域名
	if(IsIPaVailable(TarIp))				//IP
	{
		if(str2ip(ip, TarIp))		//str To num
		{
			uip_ipaddr(&ipaddr, ip[0], ip[1], ip[2], ip[3]);
			uip_ipaddr_copy(g_mconn[i].ip, ipaddr);		//記錄IP
			S282_Log("uip connecting...");
			g_mconn[i].tcp = uip_connect(&g_mconn[i].ip, htons(g_mconn[i].port)); 				
			g_mconn[i].state = TcpClient_Connectting;
			stateStamp = GetSecCnt();
		}								
	}
	else	//域名
	{				
		u8 HaveDns = 0;
		if(DhcpOk == 0)
		{
			if(dnsSel == 0)
			{		
				if(SysInfo.DnsIp1[1] != 0 && SysInfo.DnsIp1[0] != 0xff)
				{
					uip_ipaddr(ipaddr, SysInfo.DnsIp1[0],SysInfo.DnsIp1[1],SysInfo.DnsIp1[2],SysInfo.DnsIp1[3]);
					HaveDns = 1;
				}
				if(SysInfo.DnsIp2[1] !=0 || SysInfo.DnsIp1[2] !=0 )	
				{
					dnsSel = 1;
				}
			}
			if((HaveDns == 0) && dnsSel)
			{	//DNS2
				dnsSel = 0;
				if(SysInfo.DnsIp2[1] != 0 && SysInfo.DnsIp2[0] != 0xff)	
				{		
					uip_ipaddr(ipaddr, SysInfo.DnsIp2[0],SysInfo.DnsIp2[1],SysInfo.DnsIp2[2],SysInfo.DnsIp2[3]);
					HaveDns = 1;
				}
			}
		}
		if(HaveDns || DhcpOk)
		{//進行域名決議
			g_mconn[i].state = TcpClient_DnsRequest;
			g_mconn[i].flag &= ~e_Dns_found;
			S282_Log("Analy Target Server ip");
			if(resolv_getserver() == NULL)
			{
				resolv_conf(ipaddr);		//配置DNS服務器
			}
			g_mconn[i].dnsno = resolv_query((char*)&TarIp[0]);//請求域名決議
			g_mconn[i].dnsno |= 0x80;
			stateStamp = GetSecCnt();
		}						
	}
	return stateStamp;
}

					域名決議成功后直接連接
		g_mconn[i].tcp = uip_connect(&g_mconn[i].ip, htons(g_mconn[i].port));
		g_mconn[i].state = TcpClient_Connectting;

2. 登錄用戶 需要用戶名 密碼和設備ID
   代碼如下：

/*
	MQTT 連接
	入參 mode: 0 GPRS網路 1 以太網網路
*/
void MqttConnect(u8 mode)
{
	u8 i;
	u16 len;
	MQTTPacket_connectData mqttConnDat = MQTTPacket_connectData_initializer;
	GetMqttConnectData(m_mqttBuf,M_CLIENT);
	if(SysInfo.MqttDeviceID[MQT_TXT_DATLEN] == 0)
	{
		//設備ID為空使用IMEI碼
		for(i = 0; i < 15; i++)
		{
			m_mqttBuf[i] = g_IMEI[i];
		}
		m_mqttBuf[i] = '\0';
	}
	if(SysInfo.MqttUserName[MQT_TXT_DATLEN] == 0)
	{
		//MQTT用戶名為空 用默認值
		for(i = 0; i < 4; i++)
		{
			m_mqttBuf[i + MQTT_PWD] = mqttDef[i];
		}
		m_mqttBuf[i] = '\0';
	}
	
	if(SysInfo.MqttPwd[MQT_TXT_DATLEN] == 0)
	{
		//MQTT密碼為空 用默認值
		for(i = 0; i < 4; i++)
		{
			m_mqttBuf[i + MQTT_PWD * 2] = mqttDef[i];
		}
		m_mqttBuf[i] = '\0';
	}
	
	mqttConnDat.clientID.cstring = (char *)m_mqttBuf;
	//心跳存活時間根據平臺需求設定
	mqttConnDat.keepAliveInterval = SysInfo.MqttRepTim;

	mqttConnDat.cleansession = 1;
	mqttConnDat.username.cstring = (char *)&m_mqttBuf[MQTT_PWD];
	mqttConnDat.password.cstring = (char *)&m_mqttBuf[MQTT_PWD * 2];

	len = MQTTSerialize_connect(m_sendBuf,MQTT_PWD * 3,&mqttConnDat);
	if(mode == 0)
	{
		SendGprsDat(m_sendBuf,len);
	}
	else
	{
		UipClient2Server(m_sendBuf,len);
	}
}

3. 訂閱主題 這里我以tlink物聯網平臺為準

/*
	MQTT訂閱主題
*/
void MqttSubscribe(u8 mode)
{
	//·服務質量
	int qos = 0;
	u16 len,i;
	GetMqttConnectData(m_mqttBuf,M_SUBSCRIBE);
	if(!ISASCCHAR(m_mqttBuf[0]))
	{//tlink平臺要求訂閱主題為序列號+"/+"
		GetMqttConnectData(m_mqttBuf,M_CLIENTID);
		if(!ISASCCHAR(m_mqttBuf[0]))
		{
			for(i = 0; i < 15; i++)
			{
				m_mqttBuf[i] = g_IMEI[i];
			}
			m_mqttBuf[i] = '\0';
		}
		for(i = 0; i < 60; i++)
		{
			if(!ISASCCHAR(m_mqttBuf[i]))
			{
				break;
			}
		}
		m_mqttBuf[i++] = '/';
		m_mqttBuf[i++] = '+';
		m_mqttBuf[i++] = '\0';
	}
	
	topicString.cstring = (char *)m_mqttBuf;

	len = MQTTSerialize_subscribe(m_sendBuf,MQTT_PWD * 3,0,PacketId,1,&topicString,&qos);
	PacketId++;
	if(mode == 0)
	{
		SendGprsDat(m_sendBuf,len);
	}
	else
	{
		UipClient2Server(m_sendBuf,len);
	}
}

4. 發送心跳包，根據自己要求隔段時間發送

/*
	MQTT Ping
	防止MQTT斷開連接
*/
void MqttPingReq(u8 mode)
{
	u16 len;
	len = MQTTSerialize_pingreq(m_mqttBuf,MQTT_PWD * 3);
	if(mode == 0)
	{
		SendGprsDat(m_mqttBuf,len);
	}
	else
	{
		UipClient2Server(m_mqttBuf,len);
	}
}

5. 發布主題 根據自己要求處理

/*
	MQTT 發布主題
	入參： InBuf 要發送的資料
	           len 發送資料長度 mode 發送方式
*/
void MqttPublish(u8 *InBuf,u16 len,u8 mode)
{
	u8 qos = 1;
	u16 i;
	
	GetMqttConnectData(m_mqttBuf,M_PUBLISH);
	if(!ISASCCHAR(m_mqttBuf[0]))
	{//沒有填寫發布主題 用IMEI碼
		GetMqttConnectData(m_mqttBuf,M_CLIENTID);
		if(!ISASCCHAR(m_mqttBuf[0]))
		{
			for(i = 0; i < 15; i++)
			{
				m_mqttBuf[i] = g_IMEI[i];
			}
			m_mqttBuf[i] = '\0';
		}		
	}
	memset(m_sendBuf,0,1000);
	topicString.cstring = (char *)m_mqttBuf;
	len = MQTTSerialize_publish(m_sendBuf, 1000, 0, qos, 0, PacketId, topicString, InBuf, len);
	PacketId++;
	if(mode == 0)
	{
		SendGprsDat(m_sendBuf,len);
	}
	else
	{
		UipClient2Server(m_sendBuf,len);
	}
}

以上是MQTT實作步驟，只要按步驟實作，基本可以完成，但也需要根據個人要求更改，