var WebSocketServer = require('ws').Server
, wss = new WebSocketServer({port: 978});
Additional information about the system:
ulimit -a | grep file
core file size (blocks, -c) 0
file size (blocks, -f) unlimited
open files (-n) 999999
file locks (-x) unlimited
The system is Ubuntu 14, 1 GB RAM with like 500 MB free on 256 connections, so memory is not an issue.
When connections come, it reaches 256 connections and then stops.