store and forward
Keeping messages on the device while offline and sending them once the connection is back.
Store and forward buffers outgoing messages in a bounded local queue while the device is disconnected and flushes them, oldest first, after reconnecting.
Examples
A greenhouse sensor reading every 60 s keeps its readings during an 8-hour outage, then sends them once the link is back.
After reconnecting, the device flushes a few queued readings per pass of
loop()so the sketch never freezes.
See also