test.rb

require 'socket'

sockpath = "/tmp/foosock"

if ARGV.first == "server"
  socket = UNIXServer.new sockpath
  begin
    while client_sock = socket.accept do
      Thread.start do
        puts "New connection"
        while line = client_sock.gets
          client_sock.write line
        end
        client_sock.close
      end
    end
  ensure
    File.unlink sockpath
  end
else
  socket = UNIXSocket.new sockpath
  Thread.start do
    while line = socket.gets
      puts line
    end
  end
  while line = gets
    socket.write line
  end
end