If somebody were to try SYN flooding cf (i.e. opening sockets until cap is reached or all resources are drained), it's a different number than the actual max number of connections.

In those kinds of DoS attacks, you spam-create half-open connections until that specific queue is filled up, and it becomes difficult for new players to connect. The already connected players can, however, stay on. So there's a specific number for half-open connections.

As for the original question: Depends on what OS the cf box is running. If it's solaris, there are two possibilities:
32-bit solaris = 256 connections
64-bit solaris = 65k limit by OS

The server probably runs either solaris 64 or linux, which would put max connections somewhere in the 5-digit range (guesstimation).