[asterisk-users] AEL2, BASE64_DECODE and hexadecimal

[Tilghman Lesher]

On Thursday 09 April 2009 04:28:16 Olivier wrote:
> 2009/4/8 Tilghman Lesher <tilghman at mail.jeffandtilghman.com>
>
> > On Tuesday 07 April 2009 23:38:08 Olivier wrote:
> > > 2009/4/7 Mark Michelson <mmichelson at digium.com>
> > >
> > > > Philipp Kempgen wrote:
> > > > > BTW (developer's question) is there a reason why SendText() resp.
> > > > > sendtext_exec() refuses to send zero-length data?
> > > >
> > > > I can't point to any specific reason. I assume that whoever wrote the
> > > > application probably thought that attempting to send zero-length data
> >
> > was
> >
> > > > pointless and that if no data were passed to the application, it
> > > > likely was due
> > > > to an error by the user.
> > >
> > > The phone I'm working on (Thomson ST2030) would display in slow
> > > blinking, inversed letters (white on black) any text received in SIP
> > > MESSAGE. Display duration is unlimited.
> > > To erase an old message, you must send a single carriage return (or
> > > maybe an empty string).
> > >
> > > I'm wondering how many phones behave like this ?
> > >
> > > Maybe, sendtext should then be refactored to accommodate this.
> >
> > What does the phone do when you send a single space?
>
> It would display it as a black rectangle : as unfortunately, this phone
> displays text in inversed color (white letters on black background), a
> single space remains visible.
>
> It seems I really need to send a carriage return ($0D in hexa) but I
> couldn't find a way to pass such string using SendText.
>
> As suggested earlier, maybe an empty SIP MESSAGE would do the trick but as
> SendText rejects empty strings, I've not tested it yet. For that, maybe I
> could try to build my own custom SIP MESSAGE, faking a true SIP MESSAGE to
> double check if an empty string would be acceptable solution ?
>
> (Note, that sending a carriage return must work as vendor handed to me a
> Wireshark capture for a "working SIP MESSAGE")

I suspect not.  You really need to send an empty message; that is, a message
with a content-length of 0.  A message containing a carriage return would
still have a content-length of 1 and would confuse the phone at worst, and
display an unprintable character, at best.

You could send an empty message in SendText with SendText(,), but chan_sip
still doesn't allow the empty message, so a code change is still necessary.

-- 
Tilghman