I have new XBEE 3 Cellular LTE-M/NB-IoT device with Hologram SIM. Connected fine with AT&T LTE with excellent signal. Use XTCU and AT commands to configure. Using Transparent mode. All seems fine. When using Hologram dashboard to send a cloud data message, I get the first message on the serial tool and I can respond to it. I see the response under all activity. Sometimes message is delayed. Challenge is when I try to send more messages after the first. Some of the subsequent messages don’t make it. Activity comes back and says that either “Message sent to device. No response back” or sometimes “Failed to connect to device to send message.” If I slow down and send a message every minute, they all make it. I’ve tried sending a message every 10 seconds and it seems like the message every 40 seconds make it. The first message after no activity seems to work without me making changes but then the next messages fail. Anyone seen this issue with other hardware or the XBEE? Anyone have any thoughts on how to troubleshoot? Observed that the connection timeout is about 30 seconds but adjusting it to 5 didn’t seem to help. Problem happens with both TCP and UDP.
This might be an issue with CAT-M/NB-IoT and less so with your hardware. The speeds on those standards are slower than you probably think and we’ve seen handshakes take something like 90 seconds before if the modem has to wake up and bring up a connection.
I think your own experiments illustrate this issue where messaging less frequently leads to higher success rates