To avoid sending duplicate logs.

The random number could have leading 0, which meant octal, but then
there could be 8 or 9, which would confuse the follow-up arithmetics.

Fixes #2769.

If we produce huge amount of logs, take only the last 10 000 of them, to
save the bandwidth.

Just to be sure, see 000efd1205fc1bc0ecd1912e77d46c8b71a703bf. This one
does not have trap, so it just might work with exit, but better safe
than sorry.

A script for running something just once.

To save bit of data if possible. Minor optimisation.

From a real authority now.

A hostname may be more generic

No need to do so, this is more lightweight.

Refs: #2703

The server now supports certificates, so start using it.