Meaning of +QMTCONN:0,1

IoT Modules GSM Module
1

Hello all,

I was struggling with getting “MQTT is initial” state of 1 in response to AT+QMTCONN?. I didn’t know what it meant and how to resolve it. After much debugging here’s what I’ve found.

This error occurs when you try to check for a connection i.e. QMTCONN? after sending a QMTOPEN command but before the response of getting the successful connection. The below two sequences of command will better explain.

Situation 1: Successful connection

AT+QMTOPEN=0,“12…url…243”,1883
OK

+QMTOPEN: 0,0

AT+QMTOPEN?
+QMTOPEN: 0,“12…url…243”,1883

AT+QMTCONN?
+QMTCONN:0,3

Situation 2: Unsuccessful connection

AT+QMTOPEN=0,“12…url…243”,1883
OK

AT+QMTOPEN?
+QMTOPEN: 0,“12…url…243”,1883

AT+QMTCONN?
+QMTCONN:0,1

So this issue occured because the response time of AT+QMTOPEN=0,“12…url…243”,1883 with +QMTOPEN: 0,0 can be many tens of seconds. And strangely if AT+QMTOPEN? gives a successful opened response when queried in this time. So with +QMTCONN:0,1 response we can see that the opening is not yet successful.

Hope this helps anyone who has faced similar issue.

2

Hi prithvi
AT+QMTOPEN? result not gives the status of the MQTT OPEN state, it gives you the information of tcp connect ID, host name and Port name.

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while after write the AT+QMTOPEN command you have to wait the complete response i.e. till the URC +QMTOPEN: ,, where result gives you the correct actual state of the MQTT open state after that only you have to send the next command.

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if the MQTT connection close automatically you will get the URC +QMTSTAT

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Quectel_GSM_MQTT_Application_Note_V1.2.pdf (518.0 KB)

attached application note for your reference.

Regards
Rahul

3

Ok, thanks Rahul. So there we have to wait for the URC? Is there any way to check the status of the open state otherwise?

4

Once broker is open successfully with the +QMTOPEN urc using AT+QMTOPEN=,“host_name”, you can check with the AT+QMTOPEN? command.

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