map $http_upgrade $connection_upgrade {
    default upgrade;
    ''      close;
}

upstream websocket {
  server ваш_ип:2000;
}

location /websocket {
    proxy_pass http://websocket;
    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "Upgrade";
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
}

keepalive_timeout 604800;
proxy_connect_timeout 604800;
proxy_send_timeout 604800;
proxy_read_timeout 604800;

var socket = new WebSocket("ws://ваш_ип_или_домен/websocket");

var socket = new WebSocket("ws://ваш_ип_или_домен:9999");