#include <stdio
.h>
#include <stdlib
.h>
#include <string
.h>
#include <
MQTTClient.h>
#include <pthread
.h>
#define ADDRESS "tcp://broker
.emqx
.io:1
883"
#define CLIENTID "
MQTT_Combined_Client"
#define PUB_TOPIC "raspberry/publish"
#define SUB_TOPIC "raspberry/subscribe"
#define QOS 1
#define TIMEOUT 10000L
#define PAYLOAD "Hello from combined client!"
// 全局客户端实例
MQTTClient client;
volatile int exit_flag = 0;
// 消息到达回调函数
int msgarrvd(void *context, char *topicName, int topicLen,
MQTTClient_message *message) {
printf("\n[SUB] Message arrived\n");
printf(" Topic: %s\n", topicName);
printf(" Message: %
.*s\n\n", message
->payloadlen, (char*)message
->payload);
MQTTClient_freeMessage(&message);
MQTTClient_free(topicName);
return 1;
}
// 连接丢失回调
void connlost(void *context, char *cause) {
printf("\n[CONN]
Connection lost! Cause: %s\n", cause);
}
// 发布线程函数
void* publisher_thread(void* arg) {
MQTTClient_message pubmsg =
MQTTClient_message_initializer;
MQTTClient_deliveryToken token;
pubmsg
.payload = PAYLOAD;
pubmsg
.payloadlen = strlen(PAYLOAD);
pubmsg
.qos = QOS;
pubmsg
.retained = 0;
while (!exit_flag) {
int rc =
MQTTClient_publishMessage(client, PUB_TOPIC, &pubmsg, &token);
if (rc !=
MQTTCLIENT_SUCCESS) {
printf("[PUB] Publish failed: %d\n", rc);
} else {
MQTTClient_waitForCompletion(client, token, TIMEOUT);
printf("[PUB] Message published: %s\n", PAYLOAD);
}
sleep(5); // 每5秒发布一次
}
return NULL;
}
int main() {
MQTTClient_
connectOptions conn_opts =
MQTTClient_
connectOptions_initializer;
pthread_t pub_thread;
int rc;
// 创建
MQTT客户端
rc =
MQTTClient_create(&client, ADDRESS, CLIENTID,
MQTTCLIENT_PERSISTENCE_NONE, NULL);
if (rc !=
MQTTCLIENT_SUCCESS) {
fprintf(stderr, "Client creation failed: %d\n", rc);
exit(EXIT_FAILURE);
}
// 设置回调函数
rc =
MQTTClient_setCallbacks(client, NULL, connlost, msgarrvd, NULL);
if (rc !=
MQTTCLIENT_SUCCESS) {
fprintf(stderr, "Callback setup failed: %d\n", rc);
MQTTClient_destroy(&client);
exit(EXIT_FAILURE);
}
// 连接配置
conn_opts
.keepAliveInterval = 20;
conn_opts
.cleansession = 1;
// 连接到代理
if ((rc =
MQTTClient_
connect(client, &conn_opts)) !=
MQTTCLIENT_SUCCESS) {
fprintf(stderr, "
Connection failed: %d\n", rc);
MQTTClient_destroy(&client);
exit(EXIT_FAILURE);
}
printf("[CONN]
Connected to %s\n", ADDRESS);
// 订阅主题
rc =
MQTTClient_subscribe(client, SUB_TOPIC, QOS);
if (rc !=
MQTTCLIENT_SUCCESS) {
fprintf(stderr, "Subscribe failed: %d\n", rc);
MQTTClient_dis
connect(client, TIMEOUT);
MQTTClient_destroy(&client);
exit(EXIT_FAILURE);
}
printf("[SUB] Subscribed to %s\n", SUB_TOPIC);
// 创建发布线程
if (pthread_create(&pub_thread, NULL, publisher_thread, NULL) != 0) {
perror("Thread creation failed");
MQTTClient_dis
connect(client, TIMEOUT);
MQTTClient_destroy(&client);
exit(EXIT_FAILURE);
}
// 主线程等待退出指令
printf("\n[SYSTEM] Running (Press Q+Enter to exit)\n");
while (getchar() != &#
39;q&#
39;) {}
exit_flag = 1;
// 清理资源
pthread_join(pub_thread, NULL);
MQTTClient_unsubscribe(client, SUB_TOPIC);
MQTTClient_dis
connect(client, TIMEOUT);
MQTTClient_destroy(&client);
printf("\n[SYSTEM] Client shutdown\n");
return EXIT_SUCCESS;
}将库<
MQTTClient.h>改为使用<mosquitto
.h>
本文针对使用paho.mqtt.c时MQTTClient_connect返回-8的问题进行了详细分析，指出该问题是由于libpaho-mqtt3c.so与头文件版本不匹配导致，并提供了解决方案，即下载相同版本的paho.mqtt.c源码并重新编译。
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