[Twisted-Python] twisted and gprs networks

Eric Spaulding els24 at cornell.edu
Mon Jan 8 11:01:08 MST 2007

In my very limited experience with GPRS and remote devices,  I would
suggest a polling model over a push.  Unless you're willing to pay for
extra vpn/static IP services to your GPRS provider,  the remote unit
will be, as you say, firewalled and should be responsible for starting
the connection to an accessible server process.

The merit of keeping the connection open is not obvious to me.

If you aren't transferring data constantly, why not have the pda poll
-open connection to server
-send PDA id, request available data.
-receive data, if available.
-close connection.
-wait n seconds

Good luck,

John Aherne wrote:
> I am looking at using PDA devices talking to a server over gprs.
> I need to push data to the PDA over elapsed timeframes that might be
> hours. Naturally during this timespan the device may have been dropped
> from the network or acquire a different IP address.
> However to push data to the PDA, I need to record the IP and port used
> by the PDA for its first contact since it is stuck behind a firewall.
> The socket needs to be kept open on the PDA so the server can keep
> responding on the same session over a period of time.
> Using straight sockets I can do this by holding the reference to the
> IP/port used by the PDA. And checking every now and then that the
> connection is still valid. But I am no comms expert and I need to keep
> track of over 100 devices and keep reliably sending messages to them
> at random intervals.
> So, I thought it might be better to use some framework for the server
> since I am no expert on sockets.
> But looking through the docs for twisted and some of the code, I can't
> see anywhere how I can get and use a reference to the port and reuse
> the open session on the PDA.
> Can I do this with twisted or should I look for some other way of
> doing what I want.
> I was thinking I could use irc with twisted but not sure if I am
> barking up the wrong tree.
> Thanks for any ideas of solving the problem.
> John Aherne
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