Any idea if PSM should drop the PDP context and the TCP/IP session information when going sleep?

My understanding is PSM should retain all these info, so when wake up, it can seamless connect back to tcp/ip session before it sleep. however, in testing, my iot modem(Qualcomm 9205/Quectel Bg95) seems dropping the PDP, MQTT connection info before it enter sleep, so when wake up, I have to re-establish everything. that seems wrong.

Anyone with experience in this?

  • Please do not cross post the same question to multiple Stack Exchange sites (stackoverflow.com/questions/61946718/…)
    – hardillb
    May 22 '20 at 7:37
  • How long are you sleeping for, and what is the keep alive time you have set of the MQTT connection? What happens if you try a shorter sleep time?
    – hardillb
    May 22 '20 at 7:49
  • sorry for the cross posting. not sure which forum to post.
    – Justin
    Jun 10 '20 at 14:03
  • no, it is not to do with the mqtt connection timing. and not to do with longer or shorter sleep time. because both adjustment will not change the behaviour. the tcp connection will be dropped on the device side once it enters PSM
    – Justin
    Jun 10 '20 at 14:04

Your TCP connection will probably expire but your registration and PDP context should stay alive. Check this out for reference. PDP is only the tunnel to enable data connections so TCP will still time out (which affects MQTT).

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