AT+KTCPSND returns CME Error 923

IoT Modules Legacy HL Series
1

I am encountering an issue similar to the one described in the forum thread. Additionally, I receive a notification, +KTCP_NOTIF: 2,4, before encountering the CME ERROR: 923. Occasionally, after hundreds of successful iterations, I suddenly see +KTCP_NOTIF: 2,4 and then CME ERROR: 923 in response to my KTCPSND command, which follows the +KTCP_NOTIF: 2,4. I expect to see “CONNECT,” after which I send the data and then terminate the session.

From my observations, the best solution seems to be deleting the session and starting a new one rather than attempting to recover it.

But before we discuss this, I have a couple of questions:

  1. Should we apply any delay between sending and receiving TCP data using AT commands? Please see in the log below time between at commands.
  2. Should we expect and process any notification / URC data after sending tcp data before sending the next data? or Should we expect to receive data first (run AT+KTCPRCV command) before sending the next data?

Please review these logs to see the sequence of AT commands I am using for TCP communication and where the CME error occurs. The logs include a comparison of successful TCP communications on the right versus failed communications on the left.

Thank you, kind regards.

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Note that, I review the A.5 How to Use TCP Commands section in the document HL78xx AT Command Reference Guide rev 22 and couldnt see any information:

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Module Im using is HL7812 with 5.5.8.0

2

for those two questions, you can refer to your hundreds of successful iterations

BTW, did you try the latest FW version?
https://source.sierrawireless.com/resources/airprime/software/hl781x-and-hl7845-firmware/hl781x-and-hl7845-firmware-release-history-item/#sthash.lghZ1HIn.iS6lydX9.dpbs

Lastly, is that problem only happens after over 100 successful data transfer?