#!/usr/bin/env python

import socket
import tornado.iostream
import tornado.ioloop

def print_message ( data ):
    print 'client received', data

s = socket.socket(socket.AF_INET,socket.SOCK_STREAM, 0)
stream = tornado.iostream.IOStream(s)
stream.connect(('localhost',2001))
stream.read_until('',print_message)
stream.write('test message')
tornado.ioloop.IOLoop().instance().start()

#!/usr/bin/env python

import tornado.ioloop
import tornado.tcpserver
import tornado.iostream
import socket
import concurrent.futures
import functools

def handle_request ( data ):
    s = socket.socket(socket.AF_INET,socket.SOCK_STREAM,0)
    out_stream = tornado.iostream.IOStream(s)
    out_stream.connect(('localhost',2002))
    future = out_stream.read_until('')
    out_stream.write(data+'')
    return future.result()

class server_a (tornado.tcpserver.TCPServer):

   def return_response ( self, in_stream, future ):
       in_stream.write(future.result()+'')

   def handle_read ( self, in_stream, data ):
       future = self.executor.submit(handle_request,data)
       future.add_done_callback(functools.partial(self.return_response,in_stream))

   def handle_stream ( self, in_stream, address ):
       in_stream.read_until('',functools.partial(self.handle_read,in_stream))

   def __init__ ( self ):
       self.executor = concurrent.futures.ProcessPoolExecutor()
       tornado.tcpserver.TCPServer.__init__(self)

server = server_a()
server.bind(2001)
server.start(0)
tornado.ioloop.IOLoop().instance().start()

#!/usr/bin/env python

import tornado.ioloop
import tornado.tcpserver
import functools

class server_b (tornado.tcpserver.TCPServer):

    def handle_read ( self, in_stream, data ):
        in_stream.write('server B read'+data+'')

    def handle_stream ( self, in_stream, address ):
       in_stream.read_until('',functools.partial(self.handle_read,in_stream))

server = server_b()
server.bind(2002)
server.start(0)
tornado.ioloop.IOLoop().instance().start()

ERROR:concurrent.futures:exception calling callback for <Future at 0x10654b890 state=finished raised OSError>
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/site-packages/concurrent/futures/_base.py", line 299, in _invoke_callbacks
    callback(self)
  File "./a.py", line 26, in return_response
    in_stream.write(future.result()+'')
  File "/usr/local/lib/python2.7/site-packages/concurrent/futures/_base.py", line 397, in result
    return self.__get_result()
  File "/usr/local/lib/python2.7/site-packages/concurrent/futures/_base.py", line 356, in __get_result
    raise self._exception
OSError: [Errno 9] Bad file descriptor

def stop_loop ( future ):
    tornado.ioloop.IOLoop.current().stop()

def handle_request ( data ):
    tornado.ioloop.IOLoop.clear_current()
    tornado.ioloop.IOLoop.clear_instance()
    s = socket.socket(socket.AF_INET,socket.SOCK_STREAM,0)
    out_stream = tornado.iostream.IOStream(s)
    out_stream.connect(('localhost',2002))
    future = out_stream.read_until('')
    future.add_done_callback(stop_loop)
    out_stream.write(data+'')
    tornado.ioloop.IOLoop.instance().start()
    return future.result()