client.rb

#!/usr/bin/ruby

require "socket"

1000.times do |n|
    puts "opening socket ##{n}"
    TCPSocket.new("client4.scl2.svc.mozilla.com", 4444)
end

$stdin.read

server.rb

#!/usr/bin/ruby
# sudo sh -c 'ulimit -n 100000; ./server.rb'

require "rubygems"
require "eventmachine"

module Server
    @@count = 0
    @@count_mutex = Mutex.new

    def post_init
        @@count_mutex.synchronize { @@count += 1 }
        puts "connect! count=#{@@count}"
    end

    def unbind
        @@count_mutex.synchronize { @@count -= 1 }
        puts "disconnect! count=#{@@count}"
    end
end

EM.epoll = true
EventMachine::run do
    EventMachine::start_server "0.0.0.0", 4444, Server
end