[Twisted-Python] txThings - simple library for CoAP protocol

[Ron Segal]

Maciej Wasilak <wasilak <at> gmail.com> writes:

> 
> Ron,
> 
> 
> Following with interest.  Seeking a CoAP Python client capability that
includes:
> - Support for IPV6 to talk directly to server motes in constrained 6LoWPAN
> WSNs. (the large IPV6 address space is for me intrinsic to the IoT concept)
> - Security for the same, so presumably DTLS.
> Both of these needed and particularly security, for any serious monitoring
> and control applications.
> 
> 
> IPv6 is my target too. In general I've managed to run some tests with
txThings and Contiki 
> powered 6LoWPAN motes. My points below:1. Twisted doesn't officially
support UDP IPv6 yet - however there was great progress lately - see ticket
#5086 (http://twistedmatrix.com/trac/ticket/5086). Someone else should
probably comment on that, but it seems to be close to the finish line
> 
> 2. You can easily add unofficial IPv6 support (basic unicast) by modifying
twisted/internet/udp.py. I'll email you the details.
> 
> 3. There is a problem with txThings IPv6 server, because in most operating
systems source address of datagram is determined in round robin fashion. It
may cause the source address of the response to be different than
destination address of the request. CoAP client drops such responses and
sends RST. I haven't solved the problem yet. However if you need only client
you should be okay for now.
> 
> 4. DTLS is currently not supported. I agree it's a must for any real life
application. There are some Python DTLS implementations out there, but I
haven't tried to use them with Twisted yet.
> 
> 5. I don't know of any non-Twisted Python CoAP libraries with full IPv6
and DTLS support. This week there was CoAP Plugtest event in Las Vegas
(ended yesterday) - when IETF Core working group publishes some report, it
might be a good summary of existing CoAP implementations. According to the
first summary DTLS plugtest had 66% success rate - which means it's a though
topic. 
> 
> 
> Best regards
> 
> Maciej Wasilak
> 
> 
> 
> 
> 
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> 

Maciej, thank you, very interesting. But I guess not such good news for the
serious use of CoAP right now.

The percentage 'pass' for interoperability tests of DTLS are perhaps no
surprise, as unless a standard is very tight there will be slightly
different interpretations.

Really appreciate your providing details for getting an IPV6 CoAP client
working with Twisted.

Best wishes

Ron