This is the library release. There are a few bug fixes and changes of behaviour for the mosquitto and the clients, but the significant part of this release is the new mosquitto MQTT client library. The library comes in three flavours: the C library, which is the main library, and C++ and Python bindings. If you're interested in helping add bindings for your favourite language, please get in touch.

The library interface (API) is to be considered experimental, although I believe the C and C++ APIs to be complete and sane. The Python bindings are a naïve attempt by a C programmer and will definitely be changing in the future to something more pythonic. I'd be extremely grateful for help from experienced python programmers to this end.

The documentation of the library is currently ongoing... There is an overview of most of the function calls and an example in the libmosquitto.3 man page, but complete coverage can be found in the mosquitto.h man page. This, combined with the class details in mosquittopp.h can be used to help use the C++ library. The python module isn't documented due to its extremely changeable state, but there is an example in the python directory.

Other changes:

  • Topics starting with a / are treated as distinct to those not starting with a /. For example, /topic/path is different to topic/path. This matches the behaviour of rsmb.
  • Correctly calculate the will QoS on a new client connection (bug #597451).
  • Add "addresses" configuration file variable as an alias of "address", for better rsmb compatibility.
  • Bridge clean_session setting is now false, to give more sensible behaviour and be more compatible with rsmb.
  • Add cleansession variable for configuring bridges.
  • Add keepalive_interval variable for bridges.
  • Remove default topic subscription for mosquitto_sub because the old behaviour was too confusing.
  • Added a C client library, which the pub and sub clients now use.
  • Added a C++ client library (bound to the C library).
  • Added a Python client library (bound to the C library).
  • Added CMake build scripts to allow the library and clients (not the broker) to be compiled natively on Windows.

Get it from the download page.

The change to using a library means that packaging mosquitto for distros is a lot more complex. This is stretching my packaging experience, so please bear with me on that front! Mosquitto will now likely consist of a number of different packages on Ubuntu at least:

  • mosquitto (the broker)
  • mosquitto-clients (mosquitto_sub, mosquitto_pub)
  • libmosquitto0 (C library)
  • libmosquitto0-dev (C library development files)
  • libmosquittopp0 (C++ library)
  • libmosquittopp0-dev (C++ library development files)
  • libmosquitto-python (Python binding)


I've been getting a few questions about the python interface. This isn't currently packaged for Ubuntu, but hopefully will be soon. There are basic python examples in the downloads at lib/python/ and misc/currentcost/gnome-panel/