c语言mqtt Ubuntu

为了在Ubuntu上使用C语言进行MQTT通讯，您需要进行以下步骤：

1. 安装MQTT库：您可以使用Paho MQTT C库进行MQTT通讯。使用以下命令可以安装此库：

sudo apt-get install libpaho-mqtt-dev

2. 编写C程序：您可以使用以下样本程序进行MQTT通讯：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>
#include <errno.h>
#include <mqtt.h>

#define SERVER_ADDRESS "localhost"
#define CLIENT_ID "testclient"
#define TOPIC "testtopic"
#define QOS 1
#define TIMEOUT 10000L

volatile int toStop = 0;

void usage(void) {
    printf("Usage: testpub [-h <broker_host>] [-p <broker_port>]\n");
    exit(EXIT_FAILURE);
}

void cfinish(int sig) {
    signal(SIGINT, NULL);
    toStop = 1;
}

int main(int argc, char* argv[]) {
    char* url = SERVER_ADDRESS;
    int port = 1883;
    int rc = 0;
    char* clientid = CLIENT_ID;
    char* topic = TOPIC;
    int qos = QOS;
    long timeout = TIMEOUT;
    MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer;
    MQTTClient client;
    MQTTClient_message pubmsg = MQTTClient_message_initializer;
    MQTTClient_deliveryToken token;
    int ch;

    while ((ch = getopt(argc, argv, "h:p:")) != -1) {
        switch (ch) {
            case 'h':
                url = optarg;
                break;
            case 'p':
                port = atoi(optarg);
                break;
            default:
                usage();
        }
    }

    MQTTClient_create(&client, url, clientid, MQTTCLIENT_PERSISTENCE_NONE, NULL);

    signal(SIGINT, cfinish);
    signal(SIGTERM, cfinish);

    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(EXIT_FAILURE);
    }

    while (!toStop) {
        char* payload = "Hello, world";
        int payloadlen = strlen(payload);
        pubmsg.payload = payload;
        pubmsg.payloadlen = payloadlen;
        pubmsg.qos = qos;
        pubmsg.retained = 0;
        MQTTClient_publishMessage(client, topic, &pubmsg, &token);
        rc = MQTTClient_waitForCompletion(client, token, timeout);
        printf("Message with delivery token %d delivered\n", token);
        sleep(1);
    }

    MQTTClient_disconnect(client, 10000);
    MQTTClient_destroy(&client);

    return rc;
}

3. 编译程序：使用以下命令可以编译程序：

gcc -o testpub testpub.c -lpaho-mqtt3c

4. 运行程序：使用以下命令可以运行程序：

./testpub

5. 测试：打开MQTT客户端，订阅“testtopic”主题，您应该会收到程序发布的消息“Hello, world”。

以上是在Ubuntu上使用C语言进行MQTT通讯的步骤。