[Twisted-Python] twisted and gprs

Carl Zmola zmola at acm.org
Tue Jan 9 22:23:21 MST 2007

John Aherne wrote:
> Phil
> Thanks for the reply.
> I'm obviously missing some obvious point I think.
I think the obvious point is that: Everything works find while the TCP 
socket is open.  The server knows everything about the client at that 
time.  Keep alives are sent  to keep the connection open. 

The only problem occurs when the connection is closed.  The client must 
be responsible for re-establishing the connection, since the server can 
not reach the client.
To make matters more fun, the client will not always know the connection 
is down unless the client is sending keep alives (with a watchdog timer 

After you figure this all out, you can worry about UDP. UDP would only 
be useful in this situation when the client is pumping data to the 
server and does not need an immediate response, since the server may not 
be able to send UDP data to the client.  A good example would be 
position updates.  The client could send position updates every minute 
via UDP and connect via TCP every 15 minutes to guarantee the messages 
got through.

You should probably get familiar with IP, UDP and TCP framing and byte 
counting if you are working with GPRS.  Bytes can start to add up if you 
don't pay attention to them.


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