SMS received very late, modem sleeping?

Hardware Librem 5
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I have used the Librem 5 daily for about two weeks recently, I’m under Mobian Trixie. I used the known trick to solve the problem of LTE connectivity (cf. thread about “LTE connectivity lost very often”).

However, there is still a problem with SMS. Most of my SMS are received with an important delay, sometimes even an hour. When I send an SMS, it often seems to fail, I see a red cross on the bottom right corner in Chatty. The only workaround I’ve found consists in performing a call. Then, I can successfully send an SMS and I receive SMS sent the last hour. Note that this problem didn’t happen with the Pinephone under Mobian, the Pinephone and the Librem 5 don’t use the same modem and the same firmware.

I don’t know whether it’s relevant. I use a SIM card, my mobile operator is Orange France.

What can I do to get some information about this problem? Do you have a better workaround to suggest? I still refuse using another phone. I abandoned Android and I don’t want to look back. Should I upgrade the firmware? Is there a community firmware?

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I ave noticed such problems also, not very often but sometimes. Very annoying.

I think the way it works is that the modem has a small internal memory where received SMS messages are kept when they arrive. Then it is the ModemManager service that is responsible for checking if there are new SMS messages and fetching them from the modem. Based on this, my guess is that the communication between ModemManager and the modem sometimes goes wrong so that ModemManager does not understand that there is a new SMS message, then that SMS is still sitting inside the modem until some point later (like when you make a call) when ModemManager finally notices that there is a new SMS.

It should be easy to at least add some ugly hack to make ModemManager periodically check that, for example every 2 minutes, then the delay would at least not be longer than 2 minutes. But I don’n know exactly how, not right now anyway.

EDIT: the above was just me guessing, it could also be that the SMS has not even arrived to the modem yet. That is something we can check by using the mmcli command to list any SMS messages currently available in the modem. Somewhere in this forum there are examples of how to do that.

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Thank you. I’m going to check your last hypothesis right now with mmcli.

P.S: mmcli -m any --messaging-list-sms doesn’t show the “late” SMS.

P.S 2: sudo systemctl restart ModemManager makes the SMS appear in Chatty after about 2 seconds.

P.S 3: sudo mmcli -m any --reset helps too, but I would like to find something faster.

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I always just turn off modem’s power saving mode since it helps keep it from having issues (in my case) at the cost of battery life.

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How do you do that?

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Thanks! I’m already testing it to see if it fixes some of my call and SMS issues.

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Verifying your APN is correct and using the 4G cell service mode should help as well.

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They are correct. Everything works (more or less, when it does), but sometimes I don’t receive SMS for a long time, and incoming calls don’t work (as if the modem is disconnected), but sometimes they work fine. I described my problems here.

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