Mailman 3 September 2008 - Twisted

[Twisted-Python] LoopingCall question : ping w/ timeout using shared variable -> problem
by Gabriel Rossetti 25 Sep '08

25 Sep '08

Hello everyone! I have written some code uses a LoopingCall to send a "ping" at regular intervals. If it hasn't received an answer before the next call, it notifies me that the destination isn't available, if it does then it does nothing. I am getting lots of "unavailables" on hosts that are, I tried augmenting the timeout (the ping interval) and it doesn't change anything. I think what is happening is I'm using a simple variable to keep the availability state and that since protocol and the LoopingCall's callback both access the variable, this causes problems. Is there a better way of doing things or am I bound to use some sort of locking mechanism? If I have to use locking, which one do you recommend? Thank you, Gabriel

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[Twisted-Python] concurrency via reactor
by Vadim Zaliva 25 Sep '08

25 Sep '08

Hi! I am writing some code which requires synchronization between several TCP clients. I have several connections and at some point I have to wait for data becoming availiable from several of them. Kind of "barrier" pattern. I am twising my head how to do it with twisted using reactor. Could somebody point me into right direction? Thanks! Vadim

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[Twisted-Python] A question about errorback failure objects
by Vasil Vangelovski 24 Sep '08

24 Sep '08

When an errorback gets called with a failure parameter what is the best way to get the stack trace (to see what lines at what files caused the error)?

2 1

[Twisted-Python] Multi-service install
by Gabriel Rossetti 24 Sep '08

24 Sep '08

Hello everyone, I have written an application that has one server and multiple clients using twisted. I would need to be able to install/run it under windows (for now) as an executable or a service. I can't have to have to install python and all the deps, this needs to be a drag-n-drop-n-execute-it-n- it-works deal, sort of like apple "app" files. I personally run each service (client) and the server as a diff. process as using twistd with one tac file seems slower. One of the services has a wx GUI too. Does anyone have any pointers/ideas/links concerning this? I saw that py2exe and freeze exists, but from the mailing list archives I couldn't tell it it really works. Thank you, Gabriel

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[Twisted-Python] failure to connect to sshsimpleserver.py
by Glen Mabey 23 Sep '08

23 Sep '08

Hello, I'm just starting to use twisted (having quickly read through the book "Twisted: Network Programming Essentials"), and I am unable to successfully use one of the example scripts: doc/conch/examples/ sshsimpleserver.py . I am using python 2.5.2 and today's svn of twisted and pycrypto on RedHat AS5 x84-64. I experienced similar results with 8.1.0 . I am able to start the server with no problem, but when I start a client that connects to it, I get: 2008-09-23 21:51:08+0000 [-] Log opened. 2008-09-23 21:51:08+0000 [-] __main__.ExampleFactory starting on 5022 2008-09-23 21:51:08+0000 [-] Starting factory <__main__.ExampleFactory instance at 0x17e60a28> 2008-09-23 21:51:10+0000 [__main__.ExampleFactory] disabling diffie- hellman-group-exchange because we cannot find moduli file 2008-09-23 21:51:10+0000 [SSHServerTransport,0,127.0.0.1] kex alg, key alg: diffie-hellman-group1-sha1 ssh-rsa 2008-09-23 21:51:10+0000 [SSHServerTransport,0,127.0.0.1] outgoing: aes256-ctr hmac-sha1 none 2008-09-23 21:51:10+0000 [SSHServerTransport,0,127.0.0.1] incoming: aes256-ctr hmac-sha1 none 2008-09-23 21:51:10+0000 [SSHServerTransport,0,127.0.0.1] Unhandled Error Traceback (most recent call last): File "/usr/DiamondBack/stow/twisted-20080923_svn-py2.5/lib/ python2.5/site-packages/twisted/python/log.py", line 51, in callWithLogger return callWithContext({"system": lp}, func, *args, **kw) File "/usr/DiamondBack/stow/twisted-20080923_svn-py2.5/lib/ python2.5/site-packages/twisted/python/log.py", line 36, in callWithContext return context.call({ILogContext: newCtx}, func, *args, **kw) File "/usr/DiamondBack/stow/twisted-20080923_svn-py2.5/lib/ python2.5/site-packages/twisted/python/context.py", line 59, in callWithContext return self.currentContext().callWithContext(ctx, func, *args, **kw) File "/usr/DiamondBack/stow/twisted-20080923_svn-py2.5/lib/ python2.5/site-packages/twisted/python/context.py", line 37, in callWithContext return func(*args,**kw) --- <exception caught here> --- File "/usr/DiamondBack/stow/twisted-20080923_svn-py2.5/lib/ python2.5/site-packages/twisted/internet/selectreactor.py", line 146, in _doReadOrWrite why = getattr(selectable, method)() File "/usr/DiamondBack/stow/twisted-20080923_svn-py2.5/lib/ python2.5/site-packages/twisted/internet/tcp.py", line 463, in doRead return self.protocol.dataReceived(data) File "/usr/DiamondBack/stow/twisted-20080923_svn-py2.5/lib/ python2.5/site-packages/twisted/conch/ssh/transport.py", line 314, in dataReceived self.dispatchMessage(messageNum, packet[1:]) File "/usr/DiamondBack/stow/twisted-20080923_svn-py2.5/lib/ python2.5/site-packages/twisted/conch/ssh/transport.py", line 329, in dispatchMessage f(payload) File "/usr/DiamondBack/stow/twisted-20080923_svn-py2.5/lib/ python2.5/site-packages/twisted/conch/ssh/transport.py", line 740, in ssh_KEX_DH_GEX_REQUEST_OLD NS(self.factory.privateKeys[self.keyAlg].sign(exchangeHash))) File "/usr/DiamondBack/stow/twisted-20080923_svn-py2.5/lib/ python2.5/site-packages/twisted/conch/ssh/keys.py", line 659, in sign signature = self.keyObject.sign(digest, '')[0] File "/usr/DiamondBack/stow/pycrypto-20080923_git-py2.5/lib/ python2.5/site-packages/Crypto/PublicKey/pubkey.py", line 76, in sign return self._sign(M, K) exceptions.TypeError: _sign() takes exactly 2 arguments (3 given) 2008-09-23 21:51:10+0000 [SSHServerTransport,0,127.0.0.1] connection lost I have tried starting the client both as 'ssh localhost -p 5022' as well as running the sshsimpleclient.py script with the same results. I have also tried connecting from a different host into the server, with the same results. Any help in resolving this issue and realizing a working example of an ssh server would be greatly appreciated. Thank you, Glen Mabey

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[Twisted-Python] UDP vs TCP for bittorrent-style file transfer
by Z. S. O. 22 Sep '08

22 Sep '08

Hi list, I'd like to revive a topic touched on in the past. I'm playing with python socket programming and decided I want to make a simplistic bittorrent clone that uses UDP instead of TCP. My main reasons for the protocol choice are (1) I don't need guaranteed in-order delivery, and (2) I need to get around NAT restrictions without making the user manually forward ports. Couple questions... 1. Are those good reasons to ditch TCP, or am I being an idiot? (Always a possibility.) 2. Even though I don't need TCP's in-order guarantee, I still need an ACKing mechanism to make sure all the packets eventually arrive. Is there any (simple) code written that accomplishes this with UDP?

4 6

[Twisted-Python] Having some kind of "finally" clause
by Vincent Bernat 22 Sep '08

22 Sep '08

Hi! I would like to do something like this with Twisted: x.open() try: x.someoperations() x.otheroperations() finally: x.close() I could do something like this : d = open_and_get_x() d.addCallback(someoperations) d.addCallback(otheroperations) d.addBoth(closeAndReRaiseIfError) return d Each callback would return x to let the next callback proceed it. However, if there is an error, I have no "x" to close in "closeAndReRaiseIfError". How can I do that? Thanks.

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[Twisted-Python] UDP & TCP
by Andre Engels 22 Sep '08

22 Sep '08

How can I program a service in Twisted that listens for both UDP and TCP traffic at the same port? I naively created two services for it, but then got into an error message because I was listening the same port twice. -- André Engels, andreengels(a)gmail.com

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[Twisted-Python] Twisted Plugins that for classes that implement interfaces
by Paul Wilson 22 Sep '08

22 Sep '08

Hi all, I'd like to be able to use the twisted plugin mechanism to extract classes that implement given interfaces. I've successfully followed the examples to get an iterator over _objects_ that provide my interfaces, but can't find a way to get just the classes. Does such a facility exist or am I going to need a rethink? Thanks in advance... Paul

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[Twisted-Python] Weekly Bug Summary
by exarkun＠twistedmatrix.com 21 Sep '08

21 Sep '08

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