Note that a “listen backlog” of 100 connections doesn’t mean that your server can only handle 100 simultaneous (or total) connections – this is instead dependent on the number of configured processes or threads. The listen backlog is a socket setting telling the kernel how to limit the number of outstanding (as yet unaccapted) connections in the listen queue of a listening socket. If the number of pending connections exceeds the specified size, new ones are automatically rejected. A functioning server regularly servicing its connections should not require a large backlog size.
According to the manual, you can change the listen backlog with the -l option:
-l|--listen <num>
set socket listen queue to <n> (default 100, maximum is system
dependent)