The loop compared the current reading with history[1], history[2], and history[3]. The history holds the oldest reading first, so these were three of the oldest readings. A plain power failure sent no email, and the shutdown started 4 minutes late. The loop now uses the three readings before the current one.
Four tests used reading sequences that matched the old comparison. They now use plain sequences.
bmspy-ups selected its device from the devices that had data at startup, and exited with status 0 if the selection failed. One failed first read ended the monitor or made it select the wrong device.
The server has a new DEVICES command that lists the configured names, and client.list_devices calls it. bmspy-ups selects from that list and then waits for the first data of its device. A wrong or missing --device now exits with status 2. The service file does not restart on that status, because a restart cannot correct it.
An older server ends on the unknown DEVICES command, so update the server first.
The recipient check used a regular expression that never matched, so a full address got the host name appended. The main loop passed the device name with a parameter name that read_data does not have. A canceled shutdown did not clear its flag, so a second incident did not schedule a shutdown. The recorded shutdown time used the wrong unit. The --port option stayed text and never matched the STARTTLS ports.
tim