MQTT协议C语言实现与Docker容器的集成

MQTT（Message Queuing Telemetry Transport）是一种轻量级的发布/订阅消息传输协议，广泛应用于物联网场景。下面是一个简单的MQTT客户端C语言实现，并展示如何将其集成到Docker容器中。

1. MQTT客户端C语言实现

首先，我们需要一个简单的MQTT客户端实现。这里我们使用mosquitto库来实现。

安装mosquitto库

在Ubuntu上，可以使用以下命令安装mosquitto库：

sudo apt-get install libmosquitto-dev

MQTT客户端代码

创建一个名为mqtt_client.c的文件，内容如下：

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

#define Broker "tcp://broker.hivemq.com:1883"
#define ClientID "C_Client_1"

void on_connect(struct mosquitto *mosq, void *userdata, int rc) {
    printf("Connected with result code %d\n", rc);
    mosquitto_subscribe(mosq, NULL, "test/topic", 0);
}

void on_message(struct mosquitto *mosq, void *userdata, const struct mosquitto_message *msg) {
    printf("Received message: %s from topic: %s\n", msg->payload, msg->topic);
}

void on_publish(struct mosquitto *mosq, void *userdata, int mid) {
    printf("Message %d published.\n", mid);
}

void on_subscribe(struct mosquitto *mosq, void *userdata, int mid, int granted_qos) {
    printf("Subscribed: %d\n", mid);
}

void on_disconnect(struct mosquitto *mosq, void *userdata, int rc) {
    printf("Disconnected.\n");
}

int main(int argc, char *argv[]) {
    struct mosquitto *mosq;
    int rc;

    mosquitto_lib_init();

    mosq = mosquitto_new(ClientID, true, NULL);
    if (!mosq) {
        fprintf(stderr, "Failed to create mosquitto client\n");
        return 1;
    }

    mosquitto_connect(mosq, Broker, 1883, 60);
    mosquitto_set_connect_callback(mosq, on_connect);
    mosquitto_set_message_callback(mosq, on_message);
    mosquitto_set_publish_callback(mosq, on_publish);
    mosquitto_set_subscribe_callback(mosq, on_subscribe);
    mosquitto_set_disconnect_callback(mosq, on_disconnect);

    rc = mosquitto_loop_start(mosq);
    if (rc != MOSQ_ERR_SUCCESS) {
        fprintf(stderr, "Failed to start loop\n");
        return 1;
    }

    mosquitto_destroy(mosq);
    mosquitto_lib_cleanup();

    return 0;
}

2. 编译代码

创建一个名为Makefile的文件，内容如下：

CC = gcc
CFLAGS = -Wall -Wextra -o mqtt_client mqtt_client.c -lmosquitto

all: mqtt_client

mqtt_client:
	$(CC) $(CFLAGS)

clean:
	rm -f mqtt_client

运行以下命令编译代码：

make

3. Docker容器集成

创建一个名为Dockerfile的文件，内容如下：

FROM gcc

COPY . /app
WORKDIR /app

RUN apt-get update && apt-get install -y libmosquitto-dev

RUN gcc -o mqtt_client mqtt_client.c -lmosquitto

CMD ["./mqtt_client"]

创建一个名为docker-compose.yml的文件，内容如下：

version: '3'
services:
  mqtt_client:
    build: .
    ports:
      - "1883:1883"

运行以下命令构建和启动Docker容器：

docker-compose up --build

现在，你应该能够通过浏览器或其他MQTT客户端连接到tcp://localhost:1883，并订阅test/topic主题。