[Twisted-Python] How to get protocol function do not block server?

Norman Tindall NormanTindall at zdisk.net
Tue Sep 26 06:10:54 EDT 2006

   I am a newbie in twisted, sorry if this was asked thousands times

I have wrote a simple protocol (over TCP sockets) with crc32.

Suppose one client made a handshake.. and then sends to server 10Mb of
data... at the end of that 10Mb there is an crc32..

crc32 is a pretty time consuming task on a slow machine..
while server calculates crc32 of 10Mb sent by client one,
other clients can not communicate with server
(i tryed by myself to log in while transfer.. and i was wating about a
10 seconds)
And also i have a UnCryptAFrame time consuming function.

How to make those function do not block server,
to run in background, and when result is avalable call a chain of
other functions (for example it would be nice to add a callback to
Factory.handleFrame(data) with the return results of

Is it have to be deferToThread ?

And also does dataReceived blocks server by itself?
Is twisted.TCPServer scalable, can it serve 1000 - 10000 request in a
minute? (in a secound would be great :) )

-------------------------------------------------------------------------------- server.py
class MyProtocolServer(protocol.Protocol):
      # ... connectionMade ..

    def dataReceived(self, data):

        self.inp_buf += data
        if self.initialized != 0:
            self.handShake() # handshake is fast.. but i would gladly
                             # make async if i know how.

    def handleData(self):
        if self.w_len is None and len(self.inp_buf) >= 5:
            self.w_len = struct.unpack("L",self.UncryptLen(self.inp_buf[:5]))[0]
        if len(self.inp_buf) == self.w_len:
            uncrypt_frame = self.UnCryptAFrame(self.inp_buf)

    def UnCryptAFrame(self):
        # a very slow function!

class MyFactory(protocol.ServerFactory):

    protocol = MyProtocolServer

    def buildProtocol(self, addr):
        p = MyProtocolServer()
        p.factory = self
        p.addr = addr
        # ...
        return p

factory = MyFactory()

application = service.Application('myservice', uid=1, gid=1)

internet.TCPServer(9090, factory).setServiceParent(service.IServiceCollection(application))

-------------------------------------------------------------------------------- end server.py

$ twistd -ny ./f_server.py
2006/09/26 14:18 SST [-] Log opened.
2006/09/26 14:18 SST [-] twistd 2.4.0 (/usr/bin/python 2.4.2) starting up
2006/09/26 14:18 SST [-] reactor class: <class 'twisted.internet.selectreactor.SelectReactor'>
2006/09/26 14:18 SST [-] Loading ./f_server.py...
2006/09/26 14:18 SST [-] Loaded.
2006/09/26 14:18 SST [-] __builtin__.UpSTPFactory starting on 9090
2006/09/26 14:18 SST [-] Starting factory <__builtin__.UpSTPFactory instance at 0x407ec54c>
2006/09/26 14:18 SST [-] set uid/gid 1/1

In other words if i do something slow in dataReceived (of my Protocol)
it seems that it blocks server. how to avoid this?

sorry for my english :)
Best regards,
 Norman                          mailto:NormanTindall at zdisk.net

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