Install from git

1. apt-get update # Better safe than sorry
2. apt-get install libssl-dev
3. apt-get install docbook docbook-xml docbook-xsl
4. apt-get install xsltproc
5. apt-get install libsystemd-dev
6. apt install libcjson1 libcjson-dev
7. cd
8. git clone https://github.com/eclipse/mosquitto.git
9. cd mosquitto
10. vi config.mk – set WITH_SYSTEMD:=yes
11. make all (Der mangler sikkert en del dependicies - som skal installeres undervejs)
12. make install
13. adduser –system mosquitto # Bemærk det er ”-”-”system
14. ln /usr/local/lib/libmosquitto.so.1 /usr/lib/arm-linux-gnueabihf/
15. Da vi er på debian en systemd implementation ønsker vi at installere service under systemd
    1. cp /home/debian/mosquitto/service/systemd/mosquitto.service.simple /etc/systemd/system/mosquitto.service
    2. ln /usr/local/sbin/mosquitto /usr/sbin/

    3. /etc/mosquitto/mosquitto.conf # Opret tom config fil (se eksempel fil)

    4. systemctl enable mosquitto.service
    5. service mosquitto start
    6. service mosquitto status
    7. Genstart og se den er startet automatisk ( service mosquitto restart )
    8. Check grundlæggende installation
    9. mosquitto –v # i en terminal (Brooker)
    10. mosquitto_sub -v -h localhost –t "temperatur/sommerhus/stue" # i anden terminal (client/subscriber) brug evt -d for debug (Se alle feltet)
    11. mosquitto_pub -h localhost -t "temperatur/sommerhus/stue" -m "24" # i tredje terminal (client/publisher)

Example

• MQTT Broker: 93.166.84.21

//Author: [email protected]
//Date..: 19. nov 2020
//Ver...: 0.2 beta
//
//Modification:
//   01/04/2022 - Simplified: Only one mosquitto instance used in main()
//
//INFORMATION
//Mosquitto docementation:
//   - <https://mosquitto.org/documentation/>
//   - <https://github.com/eclipse/mosquitto> (Se under exanples)
//Compile with : gcc mqtt_ex1.c -lmosquitto -o mqtt_ex1
#include <stdio.h>
#include <mosquitto.h>
#include <string.h>
#include <stdlib.h>
int number;

#define SUCCES 0
void on_connect1(struct mosquitto *mosq, void *obj, int result)
{
    int rc = MOSQ_ERR_SUCCESS;

    if(result == SUCCES){
        mosquitto_subscribe(mosq, NULL, "henrik/cputemp/fahrenheit", 0);  // NOTE: Change to published topic
    }else{
        fprintf(stderr, "%s\\n", mosquitto_connack_string(result));
    }
}

void on_message1(struct mosquitto *mosq, void *obj, const struct mosquitto_message *message)
{
    struct mosquitto *mosq2 = (struct mosquitto *)obj;
        char *txtpoi, *txtpoi2;
        printf("struct mosquitto_message contains:\\n");
        printf("  mid (int).............: %i\\n", message->mid );
        printf("  topic (* char)........: %s\\n", message->topic );
        printf("  payload (* void)......: %p", message->payload );
        txtpoi = malloc(message->payloadlen + 1);
        if ( txtpoi == 0 ) {
                fprintf( stderr, "Malloc error\\n");
        } else {
                strncpy(txtpoi, message->payload, message->payloadlen);
                txtpoi[message->payloadlen] = 0;
                printf("  Message: [%s]\\n", txtpoi);
        }
        printf("  payloadlen (int)......: %i\\n", message->payloadlen );
        printf("  qos (int).............: %i\\n", message->qos );
        printf("  retain (int)..........: %i\\n", message->retain );

        txtpoi2 = malloc( message->payloadlen + 20);
        sprintf(txtpoi2, "#%i:%s", number, txtpoi);
        number++;

        mosquitto_publish(mosq, NULL, "user/DIT_NAVN_HER_ELLER_WHATEVER/english", strlen(txtpoi2), txtpoi2,  message->qos, message->retain);
        free(txtpoi2);
        free(txtpoi);
}

int main(int argc, char *argv[])
{
    struct mosquitto *mosq1;
    int version[3];
    number = 1; // Init mesage number

    mosquitto_lib_init();
    mosquitto_lib_version(&version[0],&version[1],&version[2]);
    printf("Mosquitto library version. %i.%i.%i\\n", version[0], version[1], version[2]);

    mosq1 = mosquitto_new(NULL, true, NULL);

    mosquitto_connect_callback_set(mosq1, on_connect1);
    mosquitto_message_callback_set(mosq1, on_message1);

    mosquitto_connect(mosq1, "127.0.0.1", 1883, 60);  // NOTE:  Replace localhost with IP address of broker

    mosquitto_loop_forever(mosq1, -1, 1);

    mosquitto_destroy(mosq1);

    mosquitto_lib_cleanup();

    return 0;
}