symbian-qemu-0.9.1-12/python-2.6.1/Lib/SocketServer.py
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     1 """Generic socket server classes.
       
     2 
       
     3 This module tries to capture the various aspects of defining a server:
       
     4 
       
     5 For socket-based servers:
       
     6 
       
     7 - address family:
       
     8         - AF_INET{,6}: IP (Internet Protocol) sockets (default)
       
     9         - AF_UNIX: Unix domain sockets
       
    10         - others, e.g. AF_DECNET are conceivable (see <socket.h>
       
    11 - socket type:
       
    12         - SOCK_STREAM (reliable stream, e.g. TCP)
       
    13         - SOCK_DGRAM (datagrams, e.g. UDP)
       
    14 
       
    15 For request-based servers (including socket-based):
       
    16 
       
    17 - client address verification before further looking at the request
       
    18         (This is actually a hook for any processing that needs to look
       
    19          at the request before anything else, e.g. logging)
       
    20 - how to handle multiple requests:
       
    21         - synchronous (one request is handled at a time)
       
    22         - forking (each request is handled by a new process)
       
    23         - threading (each request is handled by a new thread)
       
    24 
       
    25 The classes in this module favor the server type that is simplest to
       
    26 write: a synchronous TCP/IP server.  This is bad class design, but
       
    27 save some typing.  (There's also the issue that a deep class hierarchy
       
    28 slows down method lookups.)
       
    29 
       
    30 There are five classes in an inheritance diagram, four of which represent
       
    31 synchronous servers of four types:
       
    32 
       
    33         +------------+
       
    34         | BaseServer |
       
    35         +------------+
       
    36               |
       
    37               v
       
    38         +-----------+        +------------------+
       
    39         | TCPServer |------->| UnixStreamServer |
       
    40         +-----------+        +------------------+
       
    41               |
       
    42               v
       
    43         +-----------+        +--------------------+
       
    44         | UDPServer |------->| UnixDatagramServer |
       
    45         +-----------+        +--------------------+
       
    46 
       
    47 Note that UnixDatagramServer derives from UDPServer, not from
       
    48 UnixStreamServer -- the only difference between an IP and a Unix
       
    49 stream server is the address family, which is simply repeated in both
       
    50 unix server classes.
       
    51 
       
    52 Forking and threading versions of each type of server can be created
       
    53 using the ForkingMixIn and ThreadingMixIn mix-in classes.  For
       
    54 instance, a threading UDP server class is created as follows:
       
    55 
       
    56         class ThreadingUDPServer(ThreadingMixIn, UDPServer): pass
       
    57 
       
    58 The Mix-in class must come first, since it overrides a method defined
       
    59 in UDPServer! Setting the various member variables also changes
       
    60 the behavior of the underlying server mechanism.
       
    61 
       
    62 To implement a service, you must derive a class from
       
    63 BaseRequestHandler and redefine its handle() method.  You can then run
       
    64 various versions of the service by combining one of the server classes
       
    65 with your request handler class.
       
    66 
       
    67 The request handler class must be different for datagram or stream
       
    68 services.  This can be hidden by using the request handler
       
    69 subclasses StreamRequestHandler or DatagramRequestHandler.
       
    70 
       
    71 Of course, you still have to use your head!
       
    72 
       
    73 For instance, it makes no sense to use a forking server if the service
       
    74 contains state in memory that can be modified by requests (since the
       
    75 modifications in the child process would never reach the initial state
       
    76 kept in the parent process and passed to each child).  In this case,
       
    77 you can use a threading server, but you will probably have to use
       
    78 locks to avoid two requests that come in nearly simultaneous to apply
       
    79 conflicting changes to the server state.
       
    80 
       
    81 On the other hand, if you are building e.g. an HTTP server, where all
       
    82 data is stored externally (e.g. in the file system), a synchronous
       
    83 class will essentially render the service "deaf" while one request is
       
    84 being handled -- which may be for a very long time if a client is slow
       
    85 to reqd all the data it has requested.  Here a threading or forking
       
    86 server is appropriate.
       
    87 
       
    88 In some cases, it may be appropriate to process part of a request
       
    89 synchronously, but to finish processing in a forked child depending on
       
    90 the request data.  This can be implemented by using a synchronous
       
    91 server and doing an explicit fork in the request handler class
       
    92 handle() method.
       
    93 
       
    94 Another approach to handling multiple simultaneous requests in an
       
    95 environment that supports neither threads nor fork (or where these are
       
    96 too expensive or inappropriate for the service) is to maintain an
       
    97 explicit table of partially finished requests and to use select() to
       
    98 decide which request to work on next (or whether to handle a new
       
    99 incoming request).  This is particularly important for stream services
       
   100 where each client can potentially be connected for a long time (if
       
   101 threads or subprocesses cannot be used).
       
   102 
       
   103 Future work:
       
   104 - Standard classes for Sun RPC (which uses either UDP or TCP)
       
   105 - Standard mix-in classes to implement various authentication
       
   106   and encryption schemes
       
   107 - Standard framework for select-based multiplexing
       
   108 
       
   109 XXX Open problems:
       
   110 - What to do with out-of-band data?
       
   111 
       
   112 BaseServer:
       
   113 - split generic "request" functionality out into BaseServer class.
       
   114   Copyright (C) 2000  Luke Kenneth Casson Leighton <lkcl@samba.org>
       
   115 
       
   116   example: read entries from a SQL database (requires overriding
       
   117   get_request() to return a table entry from the database).
       
   118   entry is processed by a RequestHandlerClass.
       
   119 
       
   120 """
       
   121 
       
   122 # Author of the BaseServer patch: Luke Kenneth Casson Leighton
       
   123 
       
   124 # XXX Warning!
       
   125 # There is a test suite for this module, but it cannot be run by the
       
   126 # standard regression test.
       
   127 # To run it manually, run Lib/test/test_socketserver.py.
       
   128 
       
   129 __version__ = "0.4"
       
   130 
       
   131 
       
   132 import socket
       
   133 import select
       
   134 import sys
       
   135 import os
       
   136 try:
       
   137     import threading
       
   138 except ImportError:
       
   139     import dummy_threading as threading
       
   140 
       
   141 __all__ = ["TCPServer","UDPServer","ForkingUDPServer","ForkingTCPServer",
       
   142            "ThreadingUDPServer","ThreadingTCPServer","BaseRequestHandler",
       
   143            "StreamRequestHandler","DatagramRequestHandler",
       
   144            "ThreadingMixIn", "ForkingMixIn"]
       
   145 if hasattr(socket, "AF_UNIX"):
       
   146     __all__.extend(["UnixStreamServer","UnixDatagramServer",
       
   147                     "ThreadingUnixStreamServer",
       
   148                     "ThreadingUnixDatagramServer"])
       
   149 
       
   150 class BaseServer:
       
   151 
       
   152     """Base class for server classes.
       
   153 
       
   154     Methods for the caller:
       
   155 
       
   156     - __init__(server_address, RequestHandlerClass)
       
   157     - serve_forever(poll_interval=0.5)
       
   158     - shutdown()
       
   159     - handle_request()  # if you do not use serve_forever()
       
   160     - fileno() -> int   # for select()
       
   161 
       
   162     Methods that may be overridden:
       
   163 
       
   164     - server_bind()
       
   165     - server_activate()
       
   166     - get_request() -> request, client_address
       
   167     - handle_timeout()
       
   168     - verify_request(request, client_address)
       
   169     - server_close()
       
   170     - process_request(request, client_address)
       
   171     - close_request(request)
       
   172     - handle_error()
       
   173 
       
   174     Methods for derived classes:
       
   175 
       
   176     - finish_request(request, client_address)
       
   177 
       
   178     Class variables that may be overridden by derived classes or
       
   179     instances:
       
   180 
       
   181     - timeout
       
   182     - address_family
       
   183     - socket_type
       
   184     - allow_reuse_address
       
   185 
       
   186     Instance variables:
       
   187 
       
   188     - RequestHandlerClass
       
   189     - socket
       
   190 
       
   191     """
       
   192 
       
   193     timeout = None
       
   194 
       
   195     def __init__(self, server_address, RequestHandlerClass):
       
   196         """Constructor.  May be extended, do not override."""
       
   197         self.server_address = server_address
       
   198         self.RequestHandlerClass = RequestHandlerClass
       
   199         self.__is_shut_down = threading.Event()
       
   200         self.__serving = False
       
   201 
       
   202     def server_activate(self):
       
   203         """Called by constructor to activate the server.
       
   204 
       
   205         May be overridden.
       
   206 
       
   207         """
       
   208         pass
       
   209 
       
   210     def serve_forever(self, poll_interval=0.5):
       
   211         """Handle one request at a time until shutdown.
       
   212 
       
   213         Polls for shutdown every poll_interval seconds. Ignores
       
   214         self.timeout. If you need to do periodic tasks, do them in
       
   215         another thread.
       
   216         """
       
   217         self.__serving = True
       
   218         self.__is_shut_down.clear()
       
   219         while self.__serving:
       
   220             # XXX: Consider using another file descriptor or
       
   221             # connecting to the socket to wake this up instead of
       
   222             # polling. Polling reduces our responsiveness to a
       
   223             # shutdown request and wastes cpu at all other times.
       
   224             r, w, e = select.select([self], [], [], poll_interval)
       
   225             if r:
       
   226                 self._handle_request_noblock()
       
   227         self.__is_shut_down.set()
       
   228 
       
   229     def shutdown(self):
       
   230         """Stops the serve_forever loop.
       
   231 
       
   232         Blocks until the loop has finished. This must be called while
       
   233         serve_forever() is running in another thread, or it will
       
   234         deadlock.
       
   235         """
       
   236         self.__serving = False
       
   237         self.__is_shut_down.wait()
       
   238 
       
   239     # The distinction between handling, getting, processing and
       
   240     # finishing a request is fairly arbitrary.  Remember:
       
   241     #
       
   242     # - handle_request() is the top-level call.  It calls
       
   243     #   select, get_request(), verify_request() and process_request()
       
   244     # - get_request() is different for stream or datagram sockets
       
   245     # - process_request() is the place that may fork a new process
       
   246     #   or create a new thread to finish the request
       
   247     # - finish_request() instantiates the request handler class;
       
   248     #   this constructor will handle the request all by itself
       
   249 
       
   250     def handle_request(self):
       
   251         """Handle one request, possibly blocking.
       
   252 
       
   253         Respects self.timeout.
       
   254         """
       
   255         # Support people who used socket.settimeout() to escape
       
   256         # handle_request before self.timeout was available.
       
   257         timeout = self.socket.gettimeout()
       
   258         if timeout is None:
       
   259             timeout = self.timeout
       
   260         elif self.timeout is not None:
       
   261             timeout = min(timeout, self.timeout)
       
   262         fd_sets = select.select([self], [], [], timeout)
       
   263         if not fd_sets[0]:
       
   264             self.handle_timeout()
       
   265             return
       
   266         self._handle_request_noblock()
       
   267 
       
   268     def _handle_request_noblock(self):
       
   269         """Handle one request, without blocking.
       
   270 
       
   271         I assume that select.select has returned that the socket is
       
   272         readable before this function was called, so there should be
       
   273         no risk of blocking in get_request().
       
   274         """
       
   275         try:
       
   276             request, client_address = self.get_request()
       
   277         except socket.error:
       
   278             return
       
   279         if self.verify_request(request, client_address):
       
   280             try:
       
   281                 self.process_request(request, client_address)
       
   282             except:
       
   283                 self.handle_error(request, client_address)
       
   284                 self.close_request(request)
       
   285 
       
   286     def handle_timeout(self):
       
   287         """Called if no new request arrives within self.timeout.
       
   288 
       
   289         Overridden by ForkingMixIn.
       
   290         """
       
   291         pass
       
   292 
       
   293     def verify_request(self, request, client_address):
       
   294         """Verify the request.  May be overridden.
       
   295 
       
   296         Return True if we should proceed with this request.
       
   297 
       
   298         """
       
   299         return True
       
   300 
       
   301     def process_request(self, request, client_address):
       
   302         """Call finish_request.
       
   303 
       
   304         Overridden by ForkingMixIn and ThreadingMixIn.
       
   305 
       
   306         """
       
   307         self.finish_request(request, client_address)
       
   308         self.close_request(request)
       
   309 
       
   310     def server_close(self):
       
   311         """Called to clean-up the server.
       
   312 
       
   313         May be overridden.
       
   314 
       
   315         """
       
   316         pass
       
   317 
       
   318     def finish_request(self, request, client_address):
       
   319         """Finish one request by instantiating RequestHandlerClass."""
       
   320         self.RequestHandlerClass(request, client_address, self)
       
   321 
       
   322     def close_request(self, request):
       
   323         """Called to clean up an individual request."""
       
   324         pass
       
   325 
       
   326     def handle_error(self, request, client_address):
       
   327         """Handle an error gracefully.  May be overridden.
       
   328 
       
   329         The default is to print a traceback and continue.
       
   330 
       
   331         """
       
   332         print '-'*40
       
   333         print 'Exception happened during processing of request from',
       
   334         print client_address
       
   335         import traceback
       
   336         traceback.print_exc() # XXX But this goes to stderr!
       
   337         print '-'*40
       
   338 
       
   339 
       
   340 class TCPServer(BaseServer):
       
   341 
       
   342     """Base class for various socket-based server classes.
       
   343 
       
   344     Defaults to synchronous IP stream (i.e., TCP).
       
   345 
       
   346     Methods for the caller:
       
   347 
       
   348     - __init__(server_address, RequestHandlerClass, bind_and_activate=True)
       
   349     - serve_forever(poll_interval=0.5)
       
   350     - shutdown()
       
   351     - handle_request()  # if you don't use serve_forever()
       
   352     - fileno() -> int   # for select()
       
   353 
       
   354     Methods that may be overridden:
       
   355 
       
   356     - server_bind()
       
   357     - server_activate()
       
   358     - get_request() -> request, client_address
       
   359     - handle_timeout()
       
   360     - verify_request(request, client_address)
       
   361     - process_request(request, client_address)
       
   362     - close_request(request)
       
   363     - handle_error()
       
   364 
       
   365     Methods for derived classes:
       
   366 
       
   367     - finish_request(request, client_address)
       
   368 
       
   369     Class variables that may be overridden by derived classes or
       
   370     instances:
       
   371 
       
   372     - timeout
       
   373     - address_family
       
   374     - socket_type
       
   375     - request_queue_size (only for stream sockets)
       
   376     - allow_reuse_address
       
   377 
       
   378     Instance variables:
       
   379 
       
   380     - server_address
       
   381     - RequestHandlerClass
       
   382     - socket
       
   383 
       
   384     """
       
   385 
       
   386     address_family = socket.AF_INET
       
   387 
       
   388     socket_type = socket.SOCK_STREAM
       
   389 
       
   390     request_queue_size = 5
       
   391 
       
   392     allow_reuse_address = False
       
   393 
       
   394     def __init__(self, server_address, RequestHandlerClass, bind_and_activate=True):
       
   395         """Constructor.  May be extended, do not override."""
       
   396         BaseServer.__init__(self, server_address, RequestHandlerClass)
       
   397         self.socket = socket.socket(self.address_family,
       
   398                                     self.socket_type)
       
   399         if bind_and_activate:
       
   400             self.server_bind()
       
   401             self.server_activate()
       
   402 
       
   403     def server_bind(self):
       
   404         """Called by constructor to bind the socket.
       
   405 
       
   406         May be overridden.
       
   407 
       
   408         """
       
   409         if self.allow_reuse_address:
       
   410             self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
       
   411         self.socket.bind(self.server_address)
       
   412         self.server_address = self.socket.getsockname()
       
   413 
       
   414     def server_activate(self):
       
   415         """Called by constructor to activate the server.
       
   416 
       
   417         May be overridden.
       
   418 
       
   419         """
       
   420         self.socket.listen(self.request_queue_size)
       
   421 
       
   422     def server_close(self):
       
   423         """Called to clean-up the server.
       
   424 
       
   425         May be overridden.
       
   426 
       
   427         """
       
   428         self.socket.close()
       
   429 
       
   430     def fileno(self):
       
   431         """Return socket file number.
       
   432 
       
   433         Interface required by select().
       
   434 
       
   435         """
       
   436         return self.socket.fileno()
       
   437 
       
   438     def get_request(self):
       
   439         """Get the request and client address from the socket.
       
   440 
       
   441         May be overridden.
       
   442 
       
   443         """
       
   444         return self.socket.accept()
       
   445 
       
   446     def close_request(self, request):
       
   447         """Called to clean up an individual request."""
       
   448         request.close()
       
   449 
       
   450 
       
   451 class UDPServer(TCPServer):
       
   452 
       
   453     """UDP server class."""
       
   454 
       
   455     allow_reuse_address = False
       
   456 
       
   457     socket_type = socket.SOCK_DGRAM
       
   458 
       
   459     max_packet_size = 8192
       
   460 
       
   461     def get_request(self):
       
   462         data, client_addr = self.socket.recvfrom(self.max_packet_size)
       
   463         return (data, self.socket), client_addr
       
   464 
       
   465     def server_activate(self):
       
   466         # No need to call listen() for UDP.
       
   467         pass
       
   468 
       
   469     def close_request(self, request):
       
   470         # No need to close anything.
       
   471         pass
       
   472 
       
   473 class ForkingMixIn:
       
   474 
       
   475     """Mix-in class to handle each request in a new process."""
       
   476 
       
   477     timeout = 300
       
   478     active_children = None
       
   479     max_children = 40
       
   480 
       
   481     def collect_children(self):
       
   482         """Internal routine to wait for children that have exited."""
       
   483         if self.active_children is None: return
       
   484         while len(self.active_children) >= self.max_children:
       
   485             # XXX: This will wait for any child process, not just ones
       
   486             # spawned by this library. This could confuse other
       
   487             # libraries that expect to be able to wait for their own
       
   488             # children.
       
   489             try:
       
   490                 pid, status = os.waitpid(0, options=0)
       
   491             except os.error:
       
   492                 pid = None
       
   493             if pid not in self.active_children: continue
       
   494             self.active_children.remove(pid)
       
   495 
       
   496         # XXX: This loop runs more system calls than it ought
       
   497         # to. There should be a way to put the active_children into a
       
   498         # process group and then use os.waitpid(-pgid) to wait for any
       
   499         # of that set, but I couldn't find a way to allocate pgids
       
   500         # that couldn't collide.
       
   501         for child in self.active_children:
       
   502             try:
       
   503                 pid, status = os.waitpid(child, os.WNOHANG)
       
   504             except os.error:
       
   505                 pid = None
       
   506             if not pid: continue
       
   507             try:
       
   508                 self.active_children.remove(pid)
       
   509             except ValueError, e:
       
   510                 raise ValueError('%s. x=%d and list=%r' % (e.message, pid,
       
   511                                                            self.active_children))
       
   512 
       
   513     def handle_timeout(self):
       
   514         """Wait for zombies after self.timeout seconds of inactivity.
       
   515 
       
   516         May be extended, do not override.
       
   517         """
       
   518         self.collect_children()
       
   519 
       
   520     def process_request(self, request, client_address):
       
   521         """Fork a new subprocess to process the request."""
       
   522         self.collect_children()
       
   523         pid = os.fork()
       
   524         if pid:
       
   525             # Parent process
       
   526             if self.active_children is None:
       
   527                 self.active_children = []
       
   528             self.active_children.append(pid)
       
   529             self.close_request(request)
       
   530             return
       
   531         else:
       
   532             # Child process.
       
   533             # This must never return, hence os._exit()!
       
   534             try:
       
   535                 self.finish_request(request, client_address)
       
   536                 os._exit(0)
       
   537             except:
       
   538                 try:
       
   539                     self.handle_error(request, client_address)
       
   540                 finally:
       
   541                     os._exit(1)
       
   542 
       
   543 
       
   544 class ThreadingMixIn:
       
   545     """Mix-in class to handle each request in a new thread."""
       
   546 
       
   547     # Decides how threads will act upon termination of the
       
   548     # main process
       
   549     daemon_threads = False
       
   550 
       
   551     def process_request_thread(self, request, client_address):
       
   552         """Same as in BaseServer but as a thread.
       
   553 
       
   554         In addition, exception handling is done here.
       
   555 
       
   556         """
       
   557         try:
       
   558             self.finish_request(request, client_address)
       
   559             self.close_request(request)
       
   560         except:
       
   561             self.handle_error(request, client_address)
       
   562             self.close_request(request)
       
   563 
       
   564     def process_request(self, request, client_address):
       
   565         """Start a new thread to process the request."""
       
   566         t = threading.Thread(target = self.process_request_thread,
       
   567                              args = (request, client_address))
       
   568         if self.daemon_threads:
       
   569             t.setDaemon (1)
       
   570         t.start()
       
   571 
       
   572 
       
   573 class ForkingUDPServer(ForkingMixIn, UDPServer): pass
       
   574 class ForkingTCPServer(ForkingMixIn, TCPServer): pass
       
   575 
       
   576 class ThreadingUDPServer(ThreadingMixIn, UDPServer): pass
       
   577 class ThreadingTCPServer(ThreadingMixIn, TCPServer): pass
       
   578 
       
   579 if hasattr(socket, 'AF_UNIX'):
       
   580 
       
   581     class UnixStreamServer(TCPServer):
       
   582         address_family = socket.AF_UNIX
       
   583 
       
   584     class UnixDatagramServer(UDPServer):
       
   585         address_family = socket.AF_UNIX
       
   586 
       
   587     class ThreadingUnixStreamServer(ThreadingMixIn, UnixStreamServer): pass
       
   588 
       
   589     class ThreadingUnixDatagramServer(ThreadingMixIn, UnixDatagramServer): pass
       
   590 
       
   591 class BaseRequestHandler:
       
   592 
       
   593     """Base class for request handler classes.
       
   594 
       
   595     This class is instantiated for each request to be handled.  The
       
   596     constructor sets the instance variables request, client_address
       
   597     and server, and then calls the handle() method.  To implement a
       
   598     specific service, all you need to do is to derive a class which
       
   599     defines a handle() method.
       
   600 
       
   601     The handle() method can find the request as self.request, the
       
   602     client address as self.client_address, and the server (in case it
       
   603     needs access to per-server information) as self.server.  Since a
       
   604     separate instance is created for each request, the handle() method
       
   605     can define arbitrary other instance variariables.
       
   606 
       
   607     """
       
   608 
       
   609     def __init__(self, request, client_address, server):
       
   610         self.request = request
       
   611         self.client_address = client_address
       
   612         self.server = server
       
   613         try:
       
   614             self.setup()
       
   615             self.handle()
       
   616             self.finish()
       
   617         finally:
       
   618             sys.exc_traceback = None    # Help garbage collection
       
   619 
       
   620     def setup(self):
       
   621         pass
       
   622 
       
   623     def handle(self):
       
   624         pass
       
   625 
       
   626     def finish(self):
       
   627         pass
       
   628 
       
   629 
       
   630 # The following two classes make it possible to use the same service
       
   631 # class for stream or datagram servers.
       
   632 # Each class sets up these instance variables:
       
   633 # - rfile: a file object from which receives the request is read
       
   634 # - wfile: a file object to which the reply is written
       
   635 # When the handle() method returns, wfile is flushed properly
       
   636 
       
   637 
       
   638 class StreamRequestHandler(BaseRequestHandler):
       
   639 
       
   640     """Define self.rfile and self.wfile for stream sockets."""
       
   641 
       
   642     # Default buffer sizes for rfile, wfile.
       
   643     # We default rfile to buffered because otherwise it could be
       
   644     # really slow for large data (a getc() call per byte); we make
       
   645     # wfile unbuffered because (a) often after a write() we want to
       
   646     # read and we need to flush the line; (b) big writes to unbuffered
       
   647     # files are typically optimized by stdio even when big reads
       
   648     # aren't.
       
   649     rbufsize = -1
       
   650     wbufsize = 0
       
   651 
       
   652     def setup(self):
       
   653         self.connection = self.request
       
   654         self.rfile = self.connection.makefile('rb', self.rbufsize)
       
   655         self.wfile = self.connection.makefile('wb', self.wbufsize)
       
   656 
       
   657     def finish(self):
       
   658         if not self.wfile.closed:
       
   659             self.wfile.flush()
       
   660         self.wfile.close()
       
   661         self.rfile.close()
       
   662 
       
   663 
       
   664 class DatagramRequestHandler(BaseRequestHandler):
       
   665 
       
   666     # XXX Regrettably, I cannot get this working on Linux;
       
   667     # s.recvfrom() doesn't return a meaningful client address.
       
   668 
       
   669     """Define self.rfile and self.wfile for datagram sockets."""
       
   670 
       
   671     def setup(self):
       
   672         try:
       
   673             from cStringIO import StringIO
       
   674         except ImportError:
       
   675             from StringIO import StringIO
       
   676         self.packet, self.socket = self.request
       
   677         self.rfile = StringIO(self.packet)
       
   678         self.wfile = StringIO()
       
   679 
       
   680     def finish(self):
       
   681         self.socket.sendto(self.wfile.getvalue(), self.client_address)