paho mqtt c发布断线从连接

好的，如果您想在paho mqtt c中实现断线重连并重新发布消息，可以按照以下步骤进行：

1. 首先，您需要设置MQTTClient_connectOptions结构体的automaticReconnect字段为1，以启用自动重连功能：

MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer;
conn_opts.automaticReconnect = 1;

2. 接下来，您需要在while循环中不断重连并重新发布消息。以下是一个简单的代码示例：

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

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

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

    conn_opts.keepAliveInterval = 20;
    conn_opts.cleansession = 1;
    conn_opts.automaticReconnect = 1; // 启用自动重连

    while (1) {
        MQTTClient_create(&client, ADDRESS, CLIENTID, MQTTCLIENT_PERSISTENCE_NONE, NULL);
        rc = MQTTClient_connect(client, &conn_opts);
        if (rc != MQTTCLIENT_SUCCESS) {
            printf("Failed to connect, return code %d\n", rc);
            sleep(1); // 等待一段时间后重连
            continue;
        }

        pubmsg.payload = "Hello MQTT";
        pubmsg.payloadlen = strlen(pubmsg.payload);
        pubmsg.qos = QOS;
        pubmsg.retained = 0;
        MQTTClient_publishMessage(client, TOPIC, &pubmsg, &token);
        printf("Waiting for publication of %s\n"
               "on topic %s for client with ClientID: %s\n",
               "Hello MQTT", TOPIC, CLIENTID);
        rc = MQTTClient_waitForCompletion(client, token, TIMEOUT);
        printf("Message with delivery token %d delivered\n", token);

        MQTTClient_disconnect(client, 10000);
        MQTTClient_destroy(&client);
        sleep(1); // 等待一段时间后重连
    }

    return 0;
}

3. 编译并运行代码，您现在应该能够在断线后自动重连并重新发布消息到名为“test”的MQTT主题。

请注意，这只是一个简单的示例，您需要根据您的需求进行适当的修改。同时，请确保您已经正确配置了MQTT代理服务器的连接信息。