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I recently discovered the world of hacking CTF competitions. These competitions often contain a selection of individual challenges that exercise a whole range of skills related to hacking and computer security, but they all have one common goal… find the flag… which is usually just a recognisable, but hard to guess text string.

It all started after Youtube recommended a few videos from the LiveOverflow channel. That channel belongs to a German guy who’s created a large collection of short and easy to follow videos that give an excellent introduction to the subject. Then more recently I was watching another Youtube video where someone else was walking through the process of solving some of the challenges from the 2018 Google CTF competition. This video started by describing the Wired CSV challenge, where you’re given a photograph of a logic analyser connected to a chip and a CSV file containing the readings.

I immediately knew that i could solve this and had to stop the video before I got any spoilers. So I set aside a weekend and decided to see how much I could do in the same 48 hour period that I’d have had if I’d entered the real competition.
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This is my MQTT client library for Contiki.
It is completely asynchronous, starting a new process to handle communication with the message broker. It supports subscribing, publishing, authentication, will messages, keep alive pings and all three QoS levels. In short, it should be a fully functional client, though some areas haven’t been well tested yet.

See the example below for usage.
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