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<TITLE>RE: [Twisted-Python] TCP Packet Size Considerations</TITLE>
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<P><FONT SIZE=2>JP wrote:</FONT>
</P>
<P><FONT SIZE=2>> There are no such known limits. I might even go as far to say that there</FONT>
<BR><FONT SIZE=2>> are no such limits, if I were feeling daring. :) Do you have a short</FONT>
<BR><FONT SIZE=2>> program which demonstrates this behavior that you can share? </FONT>
<BR><FONT SIZE=2>> Perhaps after looking at that someone can suggest the cause of the disconnects.</FONT>
</P>
<P><FONT SIZE=2>After looking into it some more myself i realised an uncaught exception was dropping the connection but the after cutting my test code back to minimal functionality the inconsistency with received data was still there. The last 4KB of the data was received and the first 14KB discarded somewhere!</FONT></P>
<P><FONT SIZE=2>I have created a minimal example from my initial test code. Start the simpleserver with twistd.py -y simpleserver.py and just run the simpleclient.py the builder.dat file is just a nonsense file that is about 18KB in size. Testing on my machine produced a received.dat file which was 4KB in size. I am currently using Python 2.3.3 and Twisted 1.3.0. The code is as follows (and is also attached for convenient running):</FONT></P>
<P><FONT SIZE=2>### ------------ simpleclient.py ---------------------------------</FONT>
</P>
<P><FONT SIZE=2>from twisted.internet.protocol import Protocol</FONT>
<BR><FONT SIZE=2>import twisted.internet.error</FONT>
<BR><FONT SIZE=2>from simpleprotos import SimpleClientFactory</FONT>
<BR><FONT SIZE=2>factory = SimpleClientFactory()</FONT>
</P>
<P><FONT SIZE=2># open a large nonsense file to send (18KB)</FONT>
<BR><FONT SIZE=2>f = file('builder.dat')</FONT>
<BR><FONT SIZE=2>data = f.read()</FONT>
<BR><FONT SIZE=2>print len(data)</FONT>
<BR><FONT SIZE=2>f.close()</FONT>
</P>
<P><FONT SIZE=2>from twisted.internet import reactor</FONT>
<BR><FONT SIZE=2>reactor.connectTCP('127.0.0.1', 10000, factory)</FONT>
<BR><FONT SIZE=2>reactor.callLater(1.0, factory.sendMessage, data)</FONT>
<BR><FONT SIZE=2>reactor.run()</FONT>
</P>
<P><FONT SIZE=2>### ------------- end ---------------------------------------------</FONT>
</P>
<P><FONT SIZE=2>### ------------ simpleserver.py ----------------------------------</FONT>
</P>
<P><FONT SIZE=2>from twisted.application import internet # services that run TCP/SSL/etc.</FONT>
<BR><FONT SIZE=2>from twisted.application import service</FONT>
<BR><FONT SIZE=2>from simpleprotos import ServerDataConnection, SimpleFactory</FONT>
</P>
<P><FONT SIZE=2>def makeService():</FONT>
<BR><FONT SIZE=2> factory = SimpleFactory() # here we create a ConnectionManager</FONT>
<BR><FONT SIZE=2> return internet.TCPServer(10000, factory)</FONT>
</P>
<P><FONT SIZE=2>application = service.Application("Connection Manager")</FONT>
<BR><FONT SIZE=2>sc = service.IServiceCollection(application)</FONT>
<BR><FONT SIZE=2>sc.addService(makeService())</FONT>
</P>
<P><FONT SIZE=2>### ------------- end ---------------------------------------------</FONT>
</P>
<P><FONT SIZE=2>### ------------ simpleprotos.py ----------------------------------</FONT>
</P>
<P><FONT SIZE=2>from twisted.internet.protocol import ClientFactory, Factory, Protocol</FONT>
</P>
<P><FONT SIZE=2>class SimpleClientFactory(ClientFactory):</FONT>
<BR><FONT SIZE=2> def buildProtocol(self, addr):</FONT>
<BR><FONT SIZE=2> self.p = ClientDataConnection()</FONT>
<BR><FONT SIZE=2> self.p.factory = self</FONT>
<BR><FONT SIZE=2> return self.p</FONT>
<BR><FONT SIZE=2> </FONT>
<BR><FONT SIZE=2> def sendMessage(self, data):</FONT>
<BR><FONT SIZE=2> if hasattr(self, 'p'):</FONT>
<BR><FONT SIZE=2> self.p.sendData(data)</FONT>
</P>
<P><FONT SIZE=2>class SimpleFactory(Factory):</FONT>
<BR><FONT SIZE=2> def buildProtocol(self, addr):</FONT>
<BR><FONT SIZE=2> self.p = ServerDataConnection()</FONT>
<BR><FONT SIZE=2> self.p.factory = self</FONT>
<BR><FONT SIZE=2> return self.p</FONT>
</P>
<P><FONT SIZE=2>class ServerDataConnection(Protocol):</FONT>
<BR><FONT SIZE=2> def closeConnection(self):</FONT>
<BR><FONT SIZE=2> self.transport.loseConnection()</FONT>
<BR><FONT SIZE=2> </FONT>
<BR><FONT SIZE=2> def dataReceived(self, data):</FONT>
<BR><FONT SIZE=2> f = file('received.dat', 'w')</FONT>
<BR><FONT SIZE=2> f.write(data)</FONT>
<BR><FONT SIZE=2> f.close()</FONT>
</P>
<BR>
<P><FONT SIZE=2>class ClientDataConnection(Protocol):</FONT>
<BR><FONT SIZE=2> def closeConnection(self):</FONT>
<BR><FONT SIZE=2> self.transport.loseConnection()</FONT>
<BR><FONT SIZE=2> </FONT>
<BR><FONT SIZE=2> def sendData(self, data):</FONT>
<BR><FONT SIZE=2> self.transport.write(data)</FONT>
</P>
<P><FONT SIZE=2>### ------------- end ---------------------------------------------</FONT>
</P>
<P><FONT SIZE=2>Regards,</FONT>
</P>
<P><FONT SIZE=2>Grant McDonald</FONT>
</P>
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