socket.sendto / UDP problem

[Todd Walter]

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On Thu, 21 Oct 2010 17:03:58 +0100
MRAB <python at mrabarnett.plus.com> wrote:

> On 21/10/2010 15:57, Todd Walter wrote:
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> > On Thu, 21 Oct 2010 00:07:58 +0100
> > MRAB<python at mrabarnett.plus.com>  wrote:
> >
> >>>
> >> [snip]
> >>
> >> The docs for 'sendto' say:
> >>
> >>       """The socket should not be connected to a remote socket,
> >> since the destination socket is specified by address."""
> >>
> >> Could your problem be caused by you binding the socket to a source
> >> port, so it's going out both to the bound port _and_ the one given
> >> the binding?
> >>
> >> Have you tried using two sockets, one outgoing and the other
> >> incoming?
> >>
> >> BTW, your code for handling the response doesn't cope with it
> >> coming in a bit at a time. It loops discard any previous data from
> >> the previous iteration.
> >>
> >> Also, it's more Pythonic to say:
> >>
> >>       while '\r' not in response:
> >>           ...
> > I haven't bound the socket to a remote port, as I read it; it'sp
> > bound to a source port (192.168.10.2:2260, the local machine) and
> > just transmits to an address with a port glommed onu sn
> > (192.168.10.1:2002, the PLC).
> [snip]
> What I meant was that you're using 'pcSocket' for both directions and
> using .bind on it.
> 
> Try creating two sockets, 'pcInSocket' and 'pcOutSocket', and bind
> only pcOutSocket.

As it turns out, Windows will throw a 10022 if you try and .recvfrom
on an unbound port so I went back to the old way as it didn't seem to
be related to my problem.  I re-captured the packets from the utility
again and I noticed that my text string is getting s p a c e d o u t
in the datagram whereas the primary utility sends a nice cohesive
"spacedout".  My early transmissions work this way, successfully, as
well and I think it is because either Python or Windows is treating my
text strings differently than my numerical strings; more clearly when I
send "1234" it goes out "1234" and when I send "Todd" it goes out as 
"T o d d ".   This will obviously overflow the PLC and cause a reset.  

Any ideas?

Regards,

- - Todd
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