[elvin-discuss] UDP mode

Andrew Davison andrew at arrivasoftware.com
Wed May 2 21:46:32 CDT 2007


More on this UDP thing. When Sticker has encountered connection errors 
and you shut it down, it doesn't always seem to actually terminate, 
though the UI goes away. If you then run another instance it seems to 
think it's still connected so doesn't bother with the ConnRqst. Since 
then i've been always checking that the process really goes away (and 
killing it if it doesn't) and haven't had any problems.

ad

Andrew Davison wrote:
> You might think i'm crazy, but it has stopped doing it. Sticker now 
> sends an initial ConnRqst even in UDP mode, so don't bother looking 
> into it.
>
> Andrew
>
> David Arnold wrote:
>> -->"Andrew" == Andrew Davison <andrew at infradig.com> writes:
>>
>>   Andrew> Playing around in UDP mode and noticed that Sticker then does
>>   Andrew> not bother with ConnRqst/DisconnRqst messages, just blindly
>>   Andrew> starts adding subscriptions and doing notifies. Is this right?
>>
>> err, no.
>>
>> in terms of the abstract protocol:
>>
>> there is a UNotify packet, which is the only packet allowed to be used
>> outside a logical connection established using ConnRqst/ConnRply.  it is
>> intended for extremely light-weight producers, such as environmental
>> sensors, etc.
>>
>> you cannot use UNotify within an existing logical connection, and you
>> cannot use subscriptions, quenches, TestConn/ConfConn, QosRqst/QosRply,
>> SecRqst/SecRply, etc, without a logical connection.
>>
>> when a router accepts an incoming physical connection, it waits for
>> either a ConnRqst, UNotify or a timeout.  anything else should cause the
>> physical connection to be dropped.
>>
>>
>> channels can be established over any reliable, two-way transport.  by
>> default, this is TCP.
>>
>> the Mantara/DSTC code implements a fairly bogus UDP protocol module.
>> it's bogus because it doesn't deal with dropped packets (and maybe not
>> with packets larger than 64K?), and to safely implement the abstract
>> protocol, it should.
>>
>> we have occasionally talked about a "udp2" protocol which addressed
>> these failings, but it's never seemed worthwhile.
>>
>>
>> i haven't seen the behaviour you describe from Sticker before.  Sticker
>> uses Mantara's Java-Elvin classes, so i'll take a look when i get a
>> chance.
>>
>>
>>
>>
>>
>> d
>>
>>
>>   
>
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