windows c语言mqtt推送json数据

要在Windows上使用C语言进行MQTT推送JSON数据，你需要使用一个MQTT客户端库，例如 Eclipse Paho MQTT C客户端库。以下是一个简单的代码示例，演示如何使用该库在Windows上使用C语言发布JSON数据：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "MQTTClient.h"
#include "cJSON.h"

#define ADDRESS     "tcp://localhost:1883"
#define CLIENTID    "ExampleClientPub"
#define TOPIC       "json_data_topic"
#define QOS         1
#define TIMEOUT     10000L

int main(int argc, char* argv[])
{
    MQTTClient client;
    MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer;
    int rc;
    cJSON *root, *data;
    char *json_string;
    MQTTClient_message pubmsg = MQTTClient_message_initializer;
    MQTTClient_deliveryToken token;

    // Create JSON data
    root = cJSON_CreateObject();
    cJSON_AddItemToObject(root, "data", data = cJSON_CreateObject());
    cJSON_AddStringToObject(data, "name", "John");
    cJSON_AddNumberToObject(data, "age", 30);
    json_string = cJSON_Print(root);

    // Connect to MQTT broker
    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 to MQTT broker, return code %d\n", rc);
        exit(-1);
    }

    // Publish JSON data
    pubmsg.payload = json_string;
    pubmsg.payloadlen = strlen(json_string);
    pubmsg.qos = QOS;
    pubmsg.retained = 0;
    MQTTClient_publishMessage(client, TOPIC, &pubmsg, &token);
    printf("Waiting for published message to be delivered...\n");
    rc = MQTTClient_waitForCompletion(client, token, TIMEOUT);
    printf("Message with delivery token %d delivered\n", token);

    // Disconnect from MQTT broker
    MQTTClient_disconnect(client, 10000);
    MQTTClient_destroy(&client);

    // Free JSON data
    cJSON_Delete(root);
    free(json_string);

    return rc;
}

在代码中，我们使用了Eclipse Paho MQTT C客户端库来连接MQTT代理，创建一个JSON对象，将其转换为JSON字符串，然后使用MQTTClient_publishMessage函数将其发布到指定的主题。最后，我们断开与MQTT代理的连接，释放内存并退出程序。注意，你需要将代码中的ADDRESS，CLIENTID和TOPIC替换为自己的值，以便与MQTT代理正确通信。