output.txt

$ ruby socket_stuff.rb 
tcp6       0      0  localhost.6000         *.*                    LISTEN
:mri
{:read=>"foo"}
tcp6       0      0  localhost.6000         *.*                    LISTEN
tcp6       0      0  localhost.49830        localhost.6000         TIME_WAIT
:jruby
-e:1:in `new': Connection refused - Connection refused (Errno::ECONNREFUSED)
	from -e:1
$ jruby socket_stuff.rb 
tcp4       0      0  localhost.6000         *.*                    LISTEN
tcp6       0      0  localhost.49830        localhost.6000         TIME_WAIT
:mri
{:read=>"foo"}
tcp4       0      0  localhost.6000         *.*                    LISTEN
tcp6       0      0  localhost.49830        localhost.6000         TIME_WAIT
tcp4       0      0  localhost.49834        localhost.6000         TIME_WAIT
:jruby
{:read=>"foo"}
$ 

socket_stuff.rb

require "socket"

$stdout.sync = true

def wait(t)
  sleep 0.1 until t.status == "sleep"
  system "netstat -a | grep 6000"
end

s = TCPServer.new('localhost', 6000)
t = Thread.new do
  loop { 
    sock = s.accept
    p :read => sock.read
    sock.close
  }
end


code = 's=TCPSocket.new("localhost", 6000); s.write("foo"); s.close'

wait(t)

p :mri
system "ruby -r socket -e '#{code}'"

wait(t)

p :jruby
system "jruby -r socket -e '#{code}'"