[PD] pd-extended crashes sending data to SSR with tcpclient

IOhannes m zmoelnig zmoelnig at iem.at
Mon Jul 1 17:26:44 CEST 2013

Hash: SHA1

On 2013-07-01 16:40, Iain Mott wrote:
> Thanks very much IOhannes!
> The mrpeach version was being loaded by default. When I use 
> iemnet/tcpclient it doesn't crash. That's great.

it is, though i'm sometimes under the impression that mrpeach is a bit
more stable than iemnet (rather than the other way around)

> There's a difference however in the way mrpeach/tcpclient and 
> iemnet/tcpclient sends received data to its output.
> Messages from SSR received by mrpeach/tcpclient are sent to its
> output as a list (if that's the right word), for example as:
> This is easily converted to a readable XML string with "string2any
> 0 0" to get:
> <update><source id='1' level='-98.8531'/><source id='2' 
> level='-100.177'/><source id='3' level='-100.556'/><source id='4' 
> level='-98.3239'/></update>
> iemnet/tcpclient on the other hand sends individual numbers to its 
> output as a stream rather than a list.
> ....... etc.
> And there are various messages of various lengths. I guess if I
> use iemnet/tcpclient I'll need to find a different way of parsing
> these numbers.... Not my strong point with Pd!

well the point is, that TCP/IP as an underlying protocol doesn't know
anything about packets - it is stream-based, like a serial connection.
if you are relying on the packets coming out of the [tcpclient] object
as strings of the "correct" length, then your code is broken.
you *must* have a way to determine the end of an atomic junk of data
without relying on the list length.
[iemnet/tcpclient] makes this obvious from the beginning, as it will
never lure you into security of "correct length" lists (though there
is a hidden flag that gives you the same behaviour as
outputting the bytes one-by-one should actually make it easier to
re-packetize the data.

e.g. your example string looks like '0' was a delimiting character (at
least it appears at the end of the [mrpeach/tcpclient] example output).
if this is indeed the case, you only have to [list append] the
incoming bytes until you encounter "0", and then flush the buffer to
the output - this way your packages will always be of the correct length.

> I'll try the backtrace and other things you suggest and report back
> on mrpeach/tcpclient in another email.

it could well be, that it only does not crash with [iemnet/tcpclient]
because you haven't parsed the output yet...

Version: GnuPG v1.4.12 (GNU/Linux)
Comment: Using GnuPG with Icedove - http://www.enigmail.net/


More information about the Pd-list mailing list