This article is adapted to
- Learning to achieve MQTT (c) (asynchronous functions) in C language under Linux
https://blog.csdn.net/qq_43260665/article/details/88541433
The original is executed once sent a message, and then disconnected,
I put it into a mqtt achieve continuous sending a message:
Talk is cheap show me the code!
MQTT publish.cpp
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "MQTTAsync.h"
#include <unistd.h>
#define ADDRESS "tcp://localhost:1883"
#define CLIENTID "ClientPub"
#define TOPIC "MQTT"
#define PAYLOAD "Hello World!"
#define QOS 1
#define TIMEOUT 10000L
volatile MQTTAsync_token deliveredtoken;
int finished = 0;
bool is_connect = false;
void connlost(void *context, char *cause)
{
MQTTAsync client = (MQTTAsync)context;
MQTTAsync_connectOptions conn_opts = MQTTAsync_connectOptions_initializer;
int rc;
printf("\nConnection lost\n");
printf(" cause: %s\n", cause);
printf("Reconnecting\n");
conn_opts.keepAliveInterval = 20;
conn_opts.cleansession = 1;
if ((rc = MQTTAsync_connect(client, &conn_opts)) != MQTTASYNC_SUCCESS)
{
printf("Failed to start connect, return code %d\n", rc);
finished = 1;
}
}
void onDisconnect(void* context, MQTTAsync_successData* response)
{
printf("Successful disconnection\n");
finished = 1;
}
void onSend(void* context, MQTTAsync_successData* response)
{
//MQTTAsync client = (MQTTAsync)context;
//MQTTAsync_disconnectOptions opts = MQTTAsync_disconnectOptions_initializer;
//int rc;
printf("Message with token value %d delivery confirmed\n", response->token);
//opts.onSuccess = onDisconnect;
//opts.context = client;
/*
if ((rc = MQTTAsync_disconnect(client, &opts)) != MQTTASYNC_SUCCESS)
{
printf("Failed to start sendMessage, return code %d\n", rc);
exit(EXIT_FAILURE);
}
*/
}
void onConnectFailure(void* context, MQTTAsync_failureData* response)
{
printf("Connect failed, rc %d\n", response ? response->code : 0);
finished = 1;
}
void onConnect(void* context, MQTTAsync_successData* response)
{
MQTTAsync client = (MQTTAsync)context;
MQTTAsync_responseOptions opts = MQTTAsync_responseOptions_initializer;
MQTTAsync_message pubmsg = MQTTAsync_message_initializer;
int rc;
printf("Successful connection\n");
is_connect = true;
/* opts.onSuccess = onSend;
opts.context = client;
pubmsg.payload = (void*)PAYLOAD;
pubmsg.payloadlen = (int)strlen(PAYLOAD);
pubmsg.qos = QOS;
pubmsg.retained = 0;
deliveredtoken = 0;
if ((rc = MQTTAsync_sendMessage(client, TOPIC, &pubmsg, &opts)) != MQTTASYNC_SUCCESS)
{
printf("Failed to start sendMessage, return code %d\n", rc);
exit(EXIT_FAILURE);
}
*/
}
int main(int argc, char* argv[])
{
MQTTAsync client;
MQTTAsync_connectOptions conn_opts = MQTTAsync_connectOptions_initializer;
int rc;
MQTTAsync_create(&client, ADDRESS, CLIENTID, MQTTCLIENT_PERSISTENCE_NONE, NULL);
MQTTAsync_setCallbacks(client, NULL, connlost, NULL, NULL);
conn_opts.keepAliveInterval = 20;
conn_opts.cleansession = 1;
conn_opts.onSuccess = onConnect;
conn_opts.onFailure = onConnectFailure;
conn_opts.context = client;
printf("before\n");
if ((rc = MQTTAsync_connect(client, &conn_opts)) != MQTTASYNC_SUCCESS)
{
printf("Failed to start connect, return code %d\n", rc);
exit(EXIT_FAILURE);
}
printf("after\n");
printf("Waiting for publication of %s\n"
"on topic %s for client with ClientID: %s\n",
PAYLOAD, TOPIC, CLIENTID);
while(!is_connect)
{
printf("sleep\n");
usleep(10000L);
}
MQTTAsync_responseOptions opts = MQTTAsync_responseOptions_initializer;
opts.onSuccess = onSend;
opts.context = client;
while(1)
{
int rc;
printf("while1\n");
//#define MQTTAsync_message_initializer
MQTTAsync_message pubmsg = MQTTAsync_message_initializer;
pubmsg.payload = (void*)PAYLOAD;
pubmsg.payloadlen = (int)strlen(PAYLOAD);
pubmsg.qos = QOS;
pubmsg.retained = 0;
deliveredtoken = 0;
if ((rc = MQTTAsync_sendMessage(client, TOPIC, &pubmsg, &opts)) != MQTTASYNC_SUCCESS)
{
printf("Failed to start sendMessage, return code %d\n", rc);
exit(EXIT_FAILURE);
}
usleep(100000L);
}
while (!finished)
#if defined(WIN32)
Sleep(100);
#else
usleep(10000L);
#endif
MQTTAsync_destroy(&client);
return rc;
}
subscruib.cpp
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "MQTTAsync.h"
#include <unistd.h>
#define ADDRESS "tcp://localhost:1883"
#define CLIENTID "ClientSub"
#define TOPIC "MQTT"
#define PAYLOAD "Hello World!"
#define QOS 1
#define TIMEOUT 10000L
volatile MQTTAsync_token deliveredtoken;
int disc_finished = 0;
int subscribed = 0;
int finished = 0;
void connlost(void *context, char *cause)
{
MQTTAsync client = (MQTTAsync)context;
MQTTAsync_connectOptions conn_opts = MQTTAsync_connectOptions_initializer;
int rc;
printf("\nConnection lost\n");
if (cause)
printf(" cause: %s\n", cause);
printf("Reconnecting\n");
conn_opts.keepAliveInterval = 20;
conn_opts.cleansession = 1;
if ((rc = MQTTAsync_connect(client, &conn_opts)) != MQTTASYNC_SUCCESS)
{
printf("Failed to start connect, return code %d\n", rc);
finished = 1;
}
}
int msgarrvd(void *context, char *topicName, int topicLen, MQTTAsync_message *message)
{
int i;
char* payloadptr;
printf("Message arrived\n");
printf(" topic: %s\n", topicName);
printf(" message: ");
payloadptr = (char*)message->payload;
for(i=0; i<message->payloadlen; i++)
{
putchar(*payloadptr++);
}
putchar('\n');
MQTTAsync_freeMessage(&message);
MQTTAsync_free(topicName);
return 1;
}
void onDisconnect(void* context, MQTTAsync_successData* response)
{
printf("Successful disconnection\n");
disc_finished = 1;
}
void onSubscribe(void* context, MQTTAsync_successData* response)
{
printf("Subscribe succeeded\n");
subscribed = 1;
}
void onSubscribeFailure(void* context, MQTTAsync_failureData* response)
{
printf("Subscribe failed, rc %d\n", response ? response->code : 0);
finished = 1;
}
void onConnectFailure(void* context, MQTTAsync_failureData* response)
{
printf("Connect failed, rc %d\n", response ? response->code : 0);
finished = 1;
}
void onConnect(void* context, MQTTAsync_successData* response)
{
MQTTAsync client = (MQTTAsync)context;
MQTTAsync_responseOptions opts = MQTTAsync_responseOptions_initializer;
int rc;
printf("Successful connection\n");
printf("Subscribing to topic %s\nfor client %s using QoS%d\n\n"
"Press Q<Enter> to quit\n\n", TOPIC, CLIENTID, QOS);
opts.onSuccess = onSubscribe;
opts.onFailure = onSubscribeFailure;
opts.context = client;
deliveredtoken = 0;
if ((rc = MQTTAsync_subscribe(client, TOPIC, QOS, &opts)) != MQTTASYNC_SUCCESS)
{
printf("Failed to start subscribe, return code %d\n", rc);
exit(EXIT_FAILURE);
}
}
int main(int argc, char* argv[])
{
MQTTAsync client;
MQTTAsync_connectOptions conn_opts = MQTTAsync_connectOptions_initializer;
MQTTAsync_disconnectOptions disc_opts = MQTTAsync_disconnectOptions_initializer;
int rc;
int ch;
MQTTAsync_create(&client, ADDRESS, CLIENTID, MQTTCLIENT_PERSISTENCE_NONE, NULL);
MQTTAsync_setCallbacks(client, client, connlost, msgarrvd, NULL);
conn_opts.keepAliveInterval = 20;
conn_opts.cleansession = 1;
conn_opts.onSuccess = onConnect;
conn_opts.onFailure = onConnectFailure;
conn_opts.context = client;
if ((rc = MQTTAsync_connect(client, &conn_opts)) != MQTTASYNC_SUCCESS)
{
printf("Failed to start connect, return code %d\n", rc);
exit(EXIT_FAILURE);
}
while (!subscribed)
#if defined(WIN32)
Sleep(100);
#else
usleep(10000L);
#endif
if (finished)
goto exit;
do
{
ch = getchar();
} while (ch!='Q' && ch != 'q');
disc_opts.onSuccess = onDisconnect;
if ((rc = MQTTAsync_disconnect(client, &disc_opts)) != MQTTASYNC_SUCCESS)
{
printf("Failed to start disconnect, return code %d\n", rc);
exit(EXIT_FAILURE);
}
while (!disc_finished)
#if defined(WIN32)
Sleep(100);
#else
usleep(10000L);
#endif
exit:
MQTTAsync_destroy(&client);
return rc;
}