完整mqtt服务端c程序

创建一个完整的MQTT服务器C程序涉及几个核心部分，包括初始化SSL/TLS安全套接字，配置网络监听，以及处理客户端连接、消息发布和断开连接。以下是一个简化的示例，使用了Paho MQTT C客户端库：

#include <stdio.h>
#include <stdlib.h>
#include "mbedtls/mbedtls.h"
#include "paho_mqtt_common.h"

#define MQTT_SERVER_NAME "localhost"
#define MQTT_PORT 1883

typedef struct {
    mbedtls_ssl_context ssl;
    mqtt_socket_t *socket;
} mqtt_server_info;

void on_connect(mqtt_connection_t *conn, int reason_code, void *data) {
    if (reason_code == MQTT_ERR_SUCCESS) {
        printf("Connected to MQTT server.\n");
        mqtt_set_on_message(conn, on_message);
    } else {
        printf("Connection failed with code: %d\n", reason_code);
    }
}

void on_message(mqtt_connection_t *connection, const char *topic, int message_id, const unsigned char *payload, size_t payload_len, int qos, bool retain, void *context) {
    printf("Received message on topic %s: %.*s\n", topic, (int)payload_len, (char*)payload);
}

int main(int argc, char **argv) {
    mqtt_server_info info = {0};
    mqtt_init();

    // SSL/TLS setup
    info.socket = mqtt_new_socket();
    if (!info.socket) {
        perror("Failed to create socket");
        return -1;
    }

    // Connect to MQTT broker using SSL/TLS
    int result = mqtt_ssl_start(&info.ssl, info.socket, NULL, NULL, NULL);
    if (result != MQTT_ERR_SUCCESS) {
        perror("Failed to start SSL/TLS");
        return -1;
    }

    // Connect to MQTT server
    result = mqtt_ssl_connect(&info.ssl, MQTT_SERVER_NAME, MQTT_PORT, NULL);
    if (result != MQTT_ERR_SUCCESS) {
        perror("Failed to connect to MQTT server");
        return -1;
    }

    // Set callback functions for connection and message handling
    mqtt_set_on_connect(info.socket, on_connect, NULL);
    mqtt_set_on_message(info.socket, on_message, NULL);

    // Start listening for client connections
    mqtt_loop_start(info.socket);

    // Wait until interrupted
    while (true) {
        mbedtls_ssl_poll(&info.ssl, MBEDTLS_SSLPoll_ACCEPT, 500);
    }

    // Clean up when done
    mqtt_loop_stop(info.socket);
    mqtt_free_socket(info.socket);
    mqtt_deinit();

    return 0;
}