On Sat, 2010-02-06 at 17:13 +0000, exar...@twistedmatrix.com wrote: > On 04:42 pm, dar...@ontrenet.com wrote: > >Hi, > > I have a simple protocol listening on a port. I send it a text message > >(a filename) > >and the protocol tries to stream back the bytes of the file. Mostly, > >this works > >but in some cases, the receiving side receives less bytes than is > >written by: > > > >self.transport.write(bytes) > > > >I read the API which says it can receive less than expected bytes or > >messages. Why? > > That's how TCP works. Bytes you send with one call to write may be > split into two or more chunks and delivered to the remote dataReceived > separately, or bytes you send with two or more calls to write may be > combined into fewer chunks and delivered to the remote dataReceived all > as one string.
Yes, at the lower OSI layers it does. But in most modern programming languages, the notion of an I/O stream is built atop it (e.g. sockets will recombine and order the packets, but twisted does not?). So naturally, I don't want to emulate IP in my Twisted app. > > > >So how can I reliably send a sequences of bytes via "dataReceived" in > >my > >protocol? > > If you want "framing" - a byte format built on top of the basic > functionality provided by TCP, allowing you to differentiate bytes > belonging to different logical messages from each other - then you > should take a look at some of the protocols in twisted.protocols.basic > (NetstringReceiver, Int32StringReceiver, etc) or twisted.protocols.amp > which expands on this idea to a much greater degree. Ok, cool. I thought this would be easier in Twisted, but I will research it more. > > You can read a lot more about these ideas in this series of articles by > Itamar Turner-Trauring: > > http://www.xml.com/pub/au/215 Thanks again. > > Jean-Paul > > _______________________________________________ > Twisted-Python mailing list > Twisted-Python@twistedmatrix.com > http://twistedmatrix.com/cgi-bin/mailman/listinfo/twisted-python
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