ListenBacklog
511
The maximum length of the queue of pending connections.
Generally no tuning is needed or desired, however on some systems
it is desirable to increase this when under a TCP SYN flood attack.
See the backlog parameter to the listen(2)
system
call.
This will often be limited to a smaller number by the operating system. This varies from OS to OS. Also note that many OSes do not use exactly what is specified as the backlog, but use a number based on (but normally larger than) what is set.