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在C语言中,优化MQTT客户端的连接建立过程可以从以下几个方面进行:
具体实现上,可以参考以下代码示例:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <MQTTClient.h>
#define SERVER "tcp://broker.hivemq.com:1883"
#define CLIENTID "C_EXAMPLE"
#define TOPIC "test/topic"
void onConnect(MQTTClient *client, char *clientid, int rc) {
printf("Connected with result code %d\n", rc);
MQTTClient_subscribe(client, TOPIC, 0);
}
void onMessage(MQTTClient *client, char *topic, int payload_size, void *payload) {
char *message = (char *)malloc(payload_size + 1);
memcpy(message, payload, payload_size);
message[payload_size] = '\0';
printf("Received message: %s\n", message);
free(message);
}
int main(int argc, char *argv[]) {
MQTTClient client;
MQTTClient_connectOptions connOpts;
MQTTClient_message pubmsg;
MQTTClient_deliveryToken token;
MQTTClient_create(&client, SERVER, CLIENTID, MQTTCLIENT_PERSISTENCE_NONE, NULL);
connOpts.keepAliveInterval = 60;
connOpts.cleansession = 1;
connOpts.username = NULL;
connOpts.password = NULL;
MQTTClient_connect(client, &connOpts);
pubmsg.payload = (void *)"Hello MQTT!";
pubmsg.payloadlen = strlen(pubmsg.payload);
pubmsg.topic = TOPIC;
pubmsg.qos = 0;
pubmsg.retained = 0;
MQTTClient_publishMessage(client, &pubmsg, &token);
while (1) {
MQTTClient_poll(client, 1000);
if (MQTTClient_isConnected(client)) {
MQTTClient_disconnect(client, 10000);
}
}
MQTTClient_destroy(&client);
return 0;
}
以上代码示例中,使用了MQTTClient库来创建和连接MQTT客户端,并设置了连接参数和消息传输参数。在连接成功后,发送了一条消息并等待接收响应。在主循环中,使用MQTTClient_poll()
函数来处理消息传输和连接状态,并在适当的时候断开连接。
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