[Twisted-Python] Packet Fragmentation

Carl Zmola zmola at acm.org
Thu Oct 9 10:44:21 EDT 2008


The easiest way to do what you want is to put a count at the beginning  
of your message and read that many bytes. The protocols that Glyph  
suggested do this.

With TCP, you are responsible for keeping boundaries in the message.   
TCP delivers a reliable two way STREAM of data.  It hides all the  
packets and handshakes from the programmer.  Since it is reliable, the  
easiest way to make messages is to add a count to the beginning of  
your message.


Quoting Jean-Paul Calderone <exarkun at divmod.com>:

> On Thu, 09 Oct 2008 13:27:51 +0200, Vincent Bernat <bernat at luffy.cx> wrote:
>> OoO En  cette nuit nuageuse du  jeudi 09 octobre 2008,  vers 00:51, Nima
>> Ghanavatian <nimag at rogers.com> disait :
>>> I was wondering if there's any way in Twisted/Python to handle packet
>>> fragmentation.  Can I access the last fragment flag in the TCP   
>>> packet somehow?
>>> Or is there a total packet size sent with the packet automatically?
>>> If not, what would be the best way to solve this?
>> You can also use a protocol  that keeps message boundaries like UDP. UDP
>> is   reliable    and   deliver   messages   in   order    if   used   on
>> localhost.
> UDP is *not* reliable and will *not* necessarily deliver messages in order,
> *even* if used on localhost.  Please refer to Glyph's post.
> Jean-Paul
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