What determines number of simultaneous connections

Question

In a Java servlet environment, what are the factors that are the bottleneck for number of simultaneous users.

1. Number of HTTP connections the server can allow per

Answer 1

Seeing point 6, you can use these tools to see if your hardware is being the bottleneck: Assuming that you're on linux, you can use VmStat to see some statistics on your RAM usage, top or atop (depending on your distro) to see processes taking a toll in your CPU and RAM, nload and iftop to see what is consuming network bandwith, and iotop to see what is reading and writing to your disk.