如何通过Python基于select实现socket服务器？

import socket
import traceback
import select
EOL1 = b'\n\n'
EOL2 = b'\n\r\n'
socketmap = {}
r,w,e = [],[],[]
response = b'HTTP/1.0 200 OK\r\nDate: Mon, 1 Jan 1996 01:01:01 GMT\r\n'
response += b'Content-Type: text/plain\r\nContent-Length: 13\r\n\r\n'
response += b'Hello, world!'
serversocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
serversocket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
serversocket.bind(('0.0.0.0', 23456))
serversocket.listen(1)
#serversocket.setblocking(0)
listening_fileno = serversocket.fileno()
socketmap[listening_fileno] = serversocket
print 'listening_fileno',listening_fileno
try:
 while True:
  r,w,e = [],[],[]
  for fd in socketmap:
   r.append(fd)
   w.append(fd)
   e.append(fd)
  r,w,e = select.select(r,w,e,1)
  for fd in r:
   request = b''
   isocket = socketmap[fd]
   if fd == listening_fileno:
    print 'accepting'
    clientsock,clientaddr = isocket.accept()
    #clientsock.setblocking(0)
    cli_fileno = clientsock.fileno()
    r.append(cli_fileno)
    w.append(cli_fileno)
    e.append(cli_fileno)
    socketmap[cli_fileno] = clientsock
   else:
    print 'reading'
    while EOL1 not in request and EOL2 not in request:
     request += isocket.recv(1024)
    print(request.decode())
  for fd in w:
   print 'writing'
   osocket = socketmap[fd]
   osocket.send(response)
  for fd in e:
   esocket = socketmap[fd]
   print 'socket close',fd
   esocket.close()
   del socketmap[fd]
  print "no data coming"
except Exception,e:
 print traceback.print_exc()
 serversocket.close()