[sldev] Gesture client code Re: Anyone here with OpenCV experience?

John Hurliman jhurliman at jhurliman.org
Fri May 29 15:18:05 PDT 2009


My personal recommendation would be JSON (could even be LLSD structures
serialized to JSON) over a TCP pipe. All of the infrastructure is already
there in the viewer.

John

On Fri, May 29, 2009 at 3:08 PM, John Hurliman <jhurliman at jhurliman.org>wrote:

> UDP is a poor choice for creating pipes between applications. I don't know
> how OSX behaves, but the networking stack in the flavors of Linux I'm
> familiar with and all versions of Windows are designed to drop UDP packets;
> even on the loopback connection. When you hit a certain frequency of message
> delivery (which is easy to do on loopback) you will start consistently
> dropping some percentage of the data. Even if you design your protocol
> around accepting random data loss, the deterministic way that packets are
> dropped will almost always lead to unacceptable results.
>
> As a side note, there is a growing body of evidence that suggests TCP will
> outperform UDP even in cases where UDP would be the logical choice. Decades
> of testing and tuning, careful synchronization of implementations (see RFC
> 1122 and 2988 for example), hardware acceleration of the TCP/IP stack, and a
> prioritization of TCP over UDP in today's routing hardware gives it a
> seriously unfair advantage. This isn't really related to the choice of
> protocol for creating a local pipe though.
>
> John
>
>
> On Fri, May 22, 2009 at 4:23 PM, Philip Rosedale <philip at lindenlab.com>wrote:
>
>> Looks like DBus is TCP based - that still seems unneeded, I think we
>> should use UDP,  what think?
>>
>> Jan Ciger wrote:
>> > XML is definitely an overkill and certainly shouldn't be used for
>> > anything that has aspirations to be lightweight.
>> >
>> > Just use DBus - that is pretty standard and portable lightweight RPC
>> > mechanism and it is in the viewer already - it is used for passing
>> > slurls to the viewer from Linux browser.
>> >
>> > That would also allow easy scripting of the viewer in the future.
>> >
>> > Regards,
>> >
>> > Jan
>> >
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