How to authenticate paho mqtt subscriber client in C language with cloudamqp? - c

Question

I want to connect mqtt subscriber c client to cloudamqp but don't know how to authenticate with C program? Are there any other C language clients with working example. I am using linux.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "MQTTClient.h"
#define ADDRESS "tcp://buck.rmq.cloudamqp.com:1883"
#define CLIENTID "ExampleClientSub"
#define PAYLOAD "Hello World!"
#define QOS 1
#define TIMEOUT 10000L
#define USERNAME "sakhdjs"
#define PASSWORD "B7JnaMNF2evJmWpT_WZn"
char TOPIC[12];
volatile MQTTClient_deliveryToken deliveredtoken;
void delivered(void *context, MQTTClient_deliveryToken dt)
{
printf("Message with token value %d delivery confirmed\n", dt);
deliveredtoken = dt;
}
int msgarrvd(void *context, char *topicName, int topicLen, MQTTClient_message *message)
{
int i;
char* payloadptr;
printf("Message arrived\n");
printf(" topic: %s\n", topicName);
printf(" message: ");
payloadptr = message->payload;
for(i=0; i<message->payloadlen; i++)
{
putchar(*payloadptr++);
}
putchar('\n');
MQTTClient_freeMessage(&message);
MQTTClient_free(topicName);
return 1;
}
void connlost(void *context, char *cause)
{
printf("\nConnection lost\n");
printf(" cause: %s\n", cause);
}
int main(int argc, char* argv[])
{
MQTTClient client;
MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer;
int rc;
int ch;
printf("Enter toic name to subscribe ");
scanf("%s", TOPIC);
//printf("Enter host adderss with format like tcp://localhost:1883 ");
// scanf("%s", ADDRESS);
MQTTClient_create(&client, ADDRESS, CLIENTID,
MQTTCLIENT_PERSISTENCE_NONE,NULL);
conn_opts.keepAliveInterval = 20;
conn_opts.cleansession = 1;
MQTTClient_setCallbacks(client, NULL, connlost, msgarrvd, delivered);
if ((rc = MQTTClient_connect(client, &conn_opts ,USERNAME,PASSWORD)) != MQTTCLIENT_SUCCESS)
{
printf("Failed to connect, return code %d\n", rc);
exit(EXIT_FAILURE);
}
printf("Subscribing to topic %s\nfor client %s using QoS%d\n\n"
"Press Q<Enter> to quit\n\n", TOPIC, CLIENTID, QOS);
MQTTClient_subscribe(client, TOPIC, QOS);
do
{
ch = getchar();
} while(ch!='Q' && ch != 'q');
MQTTClient_unsubscribe(client, TOPIC);
MQTTClient_disconnect(client, 10000);
MQTTClient_destroy(&client);
return rc;
}
How to connect using paho mqtt subscriber and also publish? Are there any other C language clients for this purpose? Or any other way in C language with code?

Answer 1

You set the username and password fields in the MQTTClient_connectOptions structure before you pass it to the MQTTClient_connect() function.
MQTTClient_create(&client, ADDRESS, CLIENTID,
MQTTCLIENT_PERSISTENCE_NONE,NULL);
conn_opts.keepAliveInterval = 20;
conn_opts.cleansession = 1;
conn_opts.username = USERNAME
conn_opts.password = PASSWORD