帮我写段C语言代码 EC20HAL库连接MQTT服务器

好的，这里给您提供一个基于EC20HAL库连接MQTT服务器的C语言代码示例，仅供参考：

#include "stdio.h"
#include <stdlib.h>
#include "ec20_hal.h"
#include "MQTTClient.h"

#define ADDRESS     "tcp://localhost:1883"
#define CLIENTID    "ExampleClientSub"
#define TOPIC       "MQTT Examples"
#define PAYLOAD     "Hello World!"
#define QOS         1
#define TIMEOUT     10000L

int main(int argc, char *argv[])
{
    int rc = 0;
    EC20_HAL_Init(); // 初始化EC20模块

    Network network;
    MQTTClient client;
    MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer;
    MQTTClient_message msg = MQTTClient_message_initializer;
    MQTTClient_deliveryToken token;

    MQTTClient_create(&client, ADDRESS, CLIENTID,
        MQTTCLIENT_PERSISTENCE_NONE, NULL);
    conn_opts.keepAliveInterval = 20;
    conn_opts.cleansession = 1;

    if ((rc = MQTTClient_connect(client, &conn_opts)) != MQTTCLIENT_SUCCESS)
    {
        printf("Failed to connect, return code %d\n", rc);
        exit(-1);
    }
    printf("Connected to MQTT server\n");

    MQTTClient_subscribe(client, TOPIC, QOS);

    while (1)
    {
        char payload[100] = {0};
        int len = 0;
        if (EC20_HAL_MQTTReceive(&len, payload) == 0) // 从EC20接收MQTT消息
        {
            msg.payload = payload;
            msg.payloadlen = len;
            msg.qos = QOS;
            msg.retained = 0;
            MQTTClient_publishMessage(client, TOPIC, &msg, &token);
            printf("MQTT message published\n");
        }
    }

    MQTTClient_disconnect(client, 10000);
    MQTTClient_destroy(&client);
    return rc;
}

注意，这只是一个简单的示例代码，您需要根据具体的需求进行修改和完善。同时，也需要根据您的具体开发环境和硬件平台进行适当的调整。