Simple, parallel port scanner in Ruby built with connect_nonblock and IO.select.

port_scanner.rb

require 'socket'

# Set up the parameters.
PORT_RANGE = 1..512
HOST = 'archive.org'
TIME_TO_WAIT = 5 # seconds

# Create a socket for each port and initiate the nonblocking
# connect.
sockets = PORT_RANGE.map do |port|
  socket = Socket.new(:INET, :STREAM)
  remote_addr = Socket.sockaddr_in(port, HOST)

  begin
    socket.connect_nonblock(remote_addr)
  rescue Errno::EINPROGRESS
    # EINPROGRESS tells us that the connect cannot be completed immediately,
    # but is continuing in the background.
  end

  socket
end

# Set the expiration.
expiration = Time.now + TIME_TO_WAIT

loop do
  # We call IO.select and adjust the timeout each time so that we'll never
  # be waiting past the expiration.
  _, writable, _ = IO.select(nil, sockets, nil, expiration - Time.now)
  break unless writable

  writable.each do |socket|
    begin
      socket.connect_nonblock(socket.remote_address)
    rescue Errno::EISCONN
      # EISCONN tells us that the socket is already connected. Count this as a success.
      puts "#{HOST}:#{socket.remote_address.ip_port} accepts connections..."

      # Remove the socket from the array so it isn't selected multiple times.
      sockets.delete(socket)
    rescue Errno::EINVAL
      sockets.delete(socket)
    end
  end
end