Facing QMTOPEN errorcodes 2 and 3 frequently

IoT Modules LTE Standard Module
1

Hello Quectel,

I’m using the EC200U LTE chipset in my project. It is interfaced with ESP32-S3 chip via UART. I’m using MQTT protocol in my project and occasionally when trying to establish the MQTT connection I’m facing +QMTOPEN=<client_idx>,2 and +QMTOPEN=<client_idx>,3 errors even though I’m testing with the same setup. These two errors pop out randomly.

Please let me know if I’m doing something wrong or anything else needs to be added to get rid of this issue totally.

Thanks !

My AT command sequence for your reference :
[LTE_DEBUG]TURN_OFF_ECHO_CMD
[LTE_DEBUG]Command sent : ATE0
[LTE_DEBUG]6 bytes Data Received :
OK

I (4548) [LTE_DEBUG]: 6 bytes Data Received :
OK

[LTE_DEBUG]network_flag(0) | client_flag(0) | sub_flag(0) | mqtt_connected(0)
[LTE_DEBUG]MQTT_NETWORK_CLOSE
[LTE_DEBUG]Command sent : AT+QMTCLOSE=5
[LTE_DEBUG]24 bytes Data Received :
OK

+QMTCLOSE: 5,0

I (5252) [LTE_DEBUG]: 24 bytes Data Received :
OK

+QMTCLOSE: 5,0

[LTE_DEBUG]MQTT_NETWORK_OPEN
[LTE_DEBUG]Command sent : AT+QMTOPEN=5,“3.7.8.183”,1883
[LTE_DEBUG]23 bytes Data Received :
OK

+QMTOPEN: 5,0

I (5961) [LTE_DEBUG]: 23 bytes Data Received :
OK

+QMTOPEN: 5,0

[LTE_DEBUG]network_flag(1) | client_flag(0) | sub_flag(0) | mqtt_connected(0)
[LTE_DEBUG]MQTT_CLIENT_DISCONN_CMD
[LTE_DEBUG]Command sent : AT+QMTDISC=5
E (6542) [LTE_ERROR]: 9 bytes of Data Received :
ERROR

[LTE_DEBUG]MQTT_CLIENT_CONN_CMD
[LTE_DEBUG]Command sent : AT+QMTCONN=5,“GWY00100/07ebf099-2d3e-451e-9f8b-0cf34838a246”,“unimaqtt”,“T5DRIIJEBgfhjsrFkaDERkgJhswMwk4”
[LTE_DEBUG]25 bytes Data Received :
OK

+QMTCONN: 5,0,0

I (7260) [LTE_DEBUG]: 25 bytes Data Received :
OK

+QMTCONN: 5,0,0

[LTE_DEBUG]network_flag(1) | client_flag(1) | sub_flag(0) | mqtt_connected(0)
[LTE_DEBUG]MQTT_SUB_CMD
[LTE_DEBUG]Command sent : AT+QMTSUB=5,2,“GWY00100/commands”,0
[LTE_DEBUG]26 bytes Data Received :
OK

+QMTSUB: 5,2,0,0

I (8022) [LTE_DEBUG]: 26 bytes Data Received :
OK

+QMTSUB: 5,2,0,0

[LTE_DEBUG]MQTT_READ_MSG_CMD
[LTE_DEBUG]Command sent : AT+QMTRECV=5
[LTE_DEBUG]6 bytes Data Received :
OK

I (8556) [LTE_DEBUG]: 6 bytes Data Received :
OK

[LTE_DEBUG]network_flag(1) | client_flag(1) | sub_flag(1) | mqtt_connected(1)
[LTE_DEBUG]MQTT_READ_MSG_CMD
[LTE_DEBUG]Command sent : AT+QMTRECV=5
[LTE_DEBUG]6 bytes Data Received :
OK

I (9138) [LTE_DEBUG]: 6 bytes Data Received :
OK

[LTE_DEBUG]network_flag(1) | client_flag(1) | sub_flag(1) | mqtt_connected(1)
[LTE_DEBUG]MQTT_READ_MSG_CMD
[LTE_DEBUG]Command sent : AT+QMTRECV=5
[LTE_DEBUG]6 bytes Data Received :
OK

I (9717) [LTE_DEBUG]: 6 bytes Data Received :
OK

[LTE_DEBUG]network_flag(1) | client_flag(1) | sub_flag(1) | mqtt_connected(1)
[LTE_DEBUG]MQTT_READ_MSG_CMD
[LTE_DEBUG]Command sent : AT+QMTRECV=5
[LTE_DEBUG]6 bytes Data Received :
OK

2

You may need to monitor this probabilistic event and grab the debug log

3

Thanks for the response. I’m trying to understand why I’m getting that error. Sure I can grab that error when it occurs, but how do I get rid of it. From this MQTT commands reference document, it seems qmtopen error code 3 means Failed to activate PDP and error code 2 means MQTT identifier is occupied.

4

If I get +QMTOPEN=<client_idx>,2, what should I do ?

5

I recommend that you use another MQTT server for cross-validation