Since the announcement of Eclipse Paho (an Open Source project under the Machine-to-Machine umbrella at Eclipse) there has been a fair amount of excitement in the MQTT community about the availability of IBM’s C and Java client code under an Open Source license.
The initial proposal and setup stages have taken a little while, but this week the initial availability of the C client code was announced on the Paho mailing list (Java will follow shortly).
This is not intended to be a comprehensive guide – better documentation etc will emerge over time – but I thought I’d post a quick guide as a kickstart for anyone wanting to give it a look. I did this on 64-bit Ubuntu 11.10 – similar steps will apply on other Linux or UNIX platforms (note, the initial code contribution has a Makefile with rules which should work on UNIX, Windows, or z/OS).
Install the necessary packages to build code. NB git is for grabbing the source from Eclipse; build-essentials is a metapackage providing gcc etc on Ubuntu; and doxygen and optional graphviz are used for generating the documentation.
sudo apt-get install git build-essentials doxygen graphviz
Get the code from the git repository:
git clone git://git.eclipse.org/gitroot/paho/org.eclipse.paho.mqtt.c.git
Quick build for the client library and documentation:
make -f ../build/Makefile all
Once these commands complete, you should be left with subdirectories called <platform> and docs. In my case, <platform> was 64-bit Linux, so I had a binary at linux_ia64/libmqttv3c.so. There’s no “make install” rule at the moment, nor is there a rule to compile the docs so I had to run doxygen directly. In the future it would be nice to automate all of that, and also to build some test applications.
Opening docs/html/index.html in a browser reveals very nice documentation describing the client library, including some examples of how to use it. For example, in docs/html/pubasync.html there’s a complete listing for an asynchronous publisher application. I extracted that code into pubclient.c and decided to check that it worked!
gcc -Wall pubexample.c -L./linux_ia64 -lmqttv3c -lpthread -o pubexample
That command successfully built a binary called pubexample. All I needed to do was test it. The sample application assumes that an MQTT broker is available on localhost port 1883 – if you want to change that, simply modify the value of the static variable ADDRESS in pubexample.c – in my case I simply apt-get installed the mosquitto and mosquitto-clients packages onto my system, but I could equally have unzipped and run Really Small Message Broker – both start on port 1883 by default if not given alternative configuration.
Waiting for publication of Hello World! on topic MQTT Examples for client with ClientID: ExampleClientPub Message with token value 1 delivery confirmed
It was trivial to test that a subscriber (mosquitto_sub in my case) also received the publication. Job done!
Getting involved, and other news on Paho
I mentioned that the Java client contribution should appear soon. One other piece of news this week is that the project’s sandbox broker implementation – based on mosquitto – has been spun up. That was posted on the Paho mailing list, and if you want to get involved you should definitely subscribe to that; start to track the Eclipse Bugzilla for Paho; watch the Paho wiki; keep an eye on the source repositories; etc.. I’m already thinking about getting an OS X build rule sorted out. If you want to test your sample code now, you’ve got the option of a local broker, the Eclipse Paho sandbox, the mosquitto sandbox, or various other implementations.
Oh – and please leave a comment on this post if you find this information interesting, or want to discuss where things are with Paho. I’ll be hanging out on the mailing list as well.
What about Bob? (or Andy, even!)
Well, although I’ve left IBM, I’m delighted that MQTT is now going Open Source – in fact that was one of the things that I really wanted to help to achieve before I moved on. I am really pleased that I will be able to continue to contribute to both Paho and the broader Eclipse M2M Industry Working Group. I’ll be helping to update the mqtt.org community site, and heading over to EclipseCon in Virginia in a couple of weeks’ time to talk about M2M and work with our friends from the Koneki project. If you are attending EclipseCon please come say hi to me – and you may be interested in Wes Johnson’s session on MQTT and Eclipse tools.
There are very cool times ahead!