libmosquitto MQTT example

mqtt_example.c

#include <signal.h>
#include <stdio.h>
#include <stdint.h>
#include <string.h>

#include <mosquitto.h>

#define mqtt_host "localhost"
#define mqtt_port 1883

static int run = 1;

void handle_signal(int s)
{
	run = 0;
}

void connect_callback(struct mosquitto *mosq, void *obj, int result)
{
	printf("connect callback, rc=%d\n", result);
}

void message_callback(struct mosquitto *mosq, void *obj, const struct mosquitto_message *message)
{
	bool match = 0;
	printf("got message '%.*s' for topic '%s'\n", message->payloadlen, (char*) message->payload, message->topic);

	mosquitto_topic_matches_sub("/devices/wb-adc/controls/+", message->topic, &match);
	if (match) {
		printf("got message for ADC topic\n");
	}

}

int main(int argc, char *argv[])
{
	uint8_t reconnect = true;
	char clientid[24];
	struct mosquitto *mosq;
	int rc = 0;

	signal(SIGINT, handle_signal);
	signal(SIGTERM, handle_signal);

	mosquitto_lib_init();

	memset(clientid, 0, 24);
	snprintf(clientid, 23, "mysql_log_%d", getpid());
	mosq = mosquitto_new(clientid, true, 0);

	if(mosq){
		mosquitto_connect_callback_set(mosq, connect_callback);
		mosquitto_message_callback_set(mosq, message_callback);

	    rc = mosquitto_connect(mosq, mqtt_host, mqtt_port, 60);

		mosquitto_subscribe(mosq, NULL, "/devices/wb-adc/controls/+", 0);

		while(run){
			rc = mosquitto_loop(mosq, -1, 1);
			if(run && rc){
				printf("connection error!\n");
				sleep(10);
				mosquitto_reconnect(mosq);
			}
		}
		mosquitto_destroy(mosq);
	}

	mosquitto_lib_cleanup();

	return rc;
}

Missing headers for Linux:
#include <sys/types.h>
#include <unistd.h>

The variable "uint8_t reconnect = true;" was never used. Did you mean to use at line 61?

To compile:

gcc ./mqtt_example.c -lmosquitto -o mqtt_example

Thank you so much. It's very helpful for my work.