Naughty Netcat

nnc.rb

#!/usr/bin/env ruby
require 'rubygems'
require 'eventmachine'

class Client  < EventMachine::Connection
  def initialize(server)
    @server = server
    @server.client = self
    @start_time = Time.now.to_f
  end

  def receive_data(data)
    elapsed = Time.now.to_f - @start_time
    if elapsed > $degradation_delay
      delay = (elapsed - $degradation_delay) * $degradation_rate
      EventMachine::Timer.new(delay) { @server.send_data(data) }
    else
      @server.send_data(data)
    end
  end
end

class ProxyServer  < EventMachine::Connection
  attr_accessor :client
  
  def initialize(client_port)
    @client_port = client_port
  end

  def receive_data(data)
    client.send_data(data) if client
  end
  
  def post_init
    EventMachine.connect '127.0.0.1', @client_port, Client, self
  end
end

if ARGV.length < 2
  puts "Usage: ./nnc.rb <server port> <client port> <degradation delay (30s default) > <degradation rate (0.1s delay/s default)>"
  exit
end

server_port = ARGV[0].to_i
client_port = ARGV[1].to_i

$degradation_delay = (ARGV[2] || 30).to_i
$degradation_rate  = (ARGV[3] || 0.1).to_f

puts "Proxying traffic on port #{server_port} to #{client_port}"

EventMachine::run {
  EM.start_server("127.0.0.1", server_port, ProxyServer, client_port)
}