Chandana,
The error returned is MQTT_CONNECT_DISCONNECTED. As far as I can tell
this error is returned if the connection has been broken but also if no
connection has been set up at all or if the other side is not talking
MQTT (i.e. sending invalid data)
I'd suggest checking the network traffic and/or debugging the code to
see where it goes wrong.
One last thing: the code
else if (err == ERR_OK){
printf("Established Connection to MQTT broker\n");
}
is incorrect. At that point in the program the connection has almost
certainly not been established yet, only initiated. The connection is
only established if and when the callback is called with reason
MQTT_CONNECT_ACCEPTED. Your code must wait for that.
One last question, if your client runs on the same system as the
server/broker, why are you using lwip instead of using your local
system's network stack?
After reading this my guess is that the two systems are simply not able
to connect to each other.
Good luck!
Regards,
Eric.
On 8/20/24 12:49, Chandana N wrote:
Hello,
I am trying to connect the Mosquitto broker running on my local system
(linux).
The client is my mqtt program which uses lwip and is also running on
the local system.
The problem is that the client is getting created, connection is also
established and the function mqtt_client _connect returns ERR_OK as
the status.
The callback is also hit, but here the connection status returned is
not MQTT_ CONNECT_ ACCEPTED.
So, why is the status failing ? Is there any other different status
that is returned on a successful connection ?
I want to also confirm is it is possible in the first place, to
connect from the lwip client program running on local system to the
mqtt broker which is also running on the same system?
If not, I want to know if there's any updates to be made for my code
to work.
Broker runs on port 1883
lwip uses the wifi interface
I have not used the loopback IP, instead I am using the dynamic
IP(wifi) and specifying that itself as broker IP.
Attaching the code for your reference along with the logs.
Code ********************************************************************
#include <stdio.h>
#include <string.h>
#include "lwip/apps/mqtt.h"
#include "lwip/err.h"
#include "lwip/ip_addr.h"
// Define the MQTT broker address and port
#define BROKER_IP "192.168.0.100" // Replace with your MQTT broker IP
#define BROKER_PORT 1883
// Define MQTT client ID
#define CLIENT_ID "my_client_id" // Replace with your MQTT client ID
// MQTT connection callback function
void mqtt_connection_cb(mqtt_client_t *client, void *arg,
mqtt_connection_status_t status) {
if (status == MQTT_CONNECT_ACCEPTED) {
printf("Connected to MQTT broker successfully.\n");
} else {
printf("Failed to connect to MQTT broker: %d\n", status);
}
}
// Main function
int mqtt_create_connection() {
printf("Into MQTT create connection\n");
mqtt_client_t *client;
ip_addr_t broker_addr;
err_t err;
// Create a new MQTT client
client = mqtt_client_new();
if (client == NULL) {
printf("Failed to create MQTT client.\n");
return 1;
}
else{
printf("MQTT client created successfully.\n");
}
// Convert the broker IP address string to an ip_addr_t structure
ipaddr_aton(BROKER_IP, &broker_addr);
// Define the MQTT client information structure
struct mqtt_connect_client_info_t client_info = {
.client_id = CLIENT_ID,
.client_user = NULL, // No username
.client_pass = NULL, // No password
.keep_alive = 60, // Keep alive time in seconds
.will_topic = NULL, // No last will topic
.will_msg = NULL, // No last will message
.will_qos = 0, // QoS level 0 for the last will
.will_retain = 0 // Do not retain the last will
message
};
// Connect to the MQTT broker
err = mqtt_client_connect(client, &broker_addr, BROKER_PORT,
mqtt_connection_cb, NULL, &client_info);
if (err != ERR_OK) {
printf("Failed to start connection to MQTT broker: %d\n", err);
return 1;
}
else if (err == ERR_OK){
printf("Established Connection to MQTT broker\n");
}
// Loop to keep the program running and maintain the connection
while (1) {
// The loop could handle other tasks or just keep the client
running
}
// Free the MQTT client when done
mqtt_client_free(client);
return 0;
}
logs *********************************************************************
Regards,
Chandana
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