Shared object library usage in gambas

Question

I need to use mqtt protocol in gambas to get jobs done. I used mosquitto api and mosquitto-dev library then created something like that: `

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



int connectt(char *mqname,bool mqbool){
    printf("something happens...1");
    int rc;
    struct mosquitto * mosq;
    mosquitto_lib_init();
    mosq=mosquitto_new(mqname,mqbool,NULL);

    mosquitto_connect(mosq,"localhost",1883,60);
     if(rc!=0){
            printf("i cant connect to broker");
        mosquitto_destroy(mosq);
        return -1;
        
        }else if(rc==0){
        printf("Connected to broker yeey");
        return 0;
        }
        
        mosquitto_publish(mosq,NULL,"targe/test",6,"Yeey",0,false);
        mosquitto_disconnect(mosq);
        printf("something happening...2");
        mosquitto_destroy(mosq);
        mosquitto_lib_cleanup();
        printf("something happening...3");
        return 0;
int main(){
connectt("tester",true);
}

and i created shared object file with this way: 1gcc -c -g mosquit.c -lmosquitto gcc -shared -o libmosquit.so mosquit.o gcc -Llib/ -Wall -o targele mosquit.c -lmosquitto so i moved libmosquit.so file to /lib/x86_64-linux-gnu/ directory Untill here everything is fine, when i run targele it send "Yeeyt" payload but when i try it in gambas with these lines `

Library "libmosquit"
Extern connectt(mqname As String, mqbool As Boolean) As Integer

Public Sub Main()

  connectt("tester", True)

End

` it says connection estabilished but do not send payload.

I tried directy importing library from mosquitto api but i couldn't figure out gambas structures and i don't need all of those functions

score 0 · Accepted Answer · answered Dec 13 '22 at 23:05

Your code returns if rc != 0 or rc == 0 (i.e. in all cases) meaning the call to mosquitto_publish is never reached. In your case rc is never set, you define it (int rc), but do not assign anything to it i.e. rc = mosquitto_connect(mosq, "test.mosquitto.org", 1883, 60); so effectively your code is:

int rc
if (rc != 0) {
  printf("i cant connect to broker");
  mosquitto_destroy(mosq);
  return -1;
} else if (rc == 0) {
  printf("Connected to broker yeey");
  return 0;
}
// Any code below here is unreachable

When you have fixed that you may run into another issue; you might find this example useful. mosquitto_connect "makes the socket connection only, it does not complete the MQTTCONNECT/CONNACK flow, you should use mosquitto_loop_start() or mosquitto_loop_forever() for processing net traffic".

Shared object library usage in gambas

1 Answers1