Hello Everyone,
Thank you for the feedback and all the helpful comments on this thread. I wanted to chime in and provide some more information here to help everyone understand the issue and how to resolve it. At its core, the cellular network was designed for mobile communications with devices that moved around and switched from cell to cell, it was not designed for long term static connections. For this reason, and to preserve their resources, cellular towers will automatically tear down sessions that have been inactive for some time and have not been properly terminated by the cellular device. This behavior is universal across cellular towers and carriers and is not something unique to Hologram SIMs. Now, this becomes an issue when you want to have continuous inbound access to your device like you would if it were using a wired connection or WiFi.
There are a few different approaches to keeping your device connected. One would be to have your device send keep alive messages to avoid the tower deeming your device as inactive and tearing down it’s session. Otherwise it’s common for cellular devices to have to implement a watchdog to reconnect when a connection is lost (your cellphone does this all the time, for instance). The use case and device characteristics will likely determine which method is optimal for your specific situation.
For users using our SDK, please note that the send command should be use as a stand alone command and does not need the device to be in a PPP session by issuing the connect command.
For anyone using Cat-M1 I really like @AndrewGifft’s answer in this thread.
Best,
Maiky