Version 1.5.1 released

This is a bugfix release.

Packaging changes

  • The snap package now has support for websockets included.
  • The Windows packages have changed.
    • Support for Windows XP was dropped in Mosquitto 1.5, so the need for the Cygwin build has gone, and this has been dropped.
    • There are now 64-bit and 32-bit native packages.
    • Websockets support is included.
    • Threading support is not included in libmosquitto to simplify installation, alternative solutions are being looked into for the future.
    • The only external dependency is now OpenSSL.

Version 1.5.1 changes


  • Fix plugin cleanup function not being called on exit of the broker. Closes #900.
  • Print more OpenSSL errors when loading certificates/keys fail.
  • Use AF_UNSPEC etc. instead of PF_UNSPEC to comply with POSIX. Closes #863.
  • Remove use of AI_ADDRCONFIG, which means the broker can be used on systems where only the loopback interface is defined. Closes #869, Closes #901.
  • Fix IPv6 addresses not being able to be used as bridge addresses. Closes #886.
  • All clients now time out if they exceed their keepalive*1.5, rather than just reach it. This was inconsistent in two places.
  • Fix segfault on startup if bridge CA certificates could not be read. Closes #851.
  • Fix problem opening listeners on Pi caused by unsigned char being default. Found via #849.
  • ACL patterns that do not contain either %c or %u now produce a warning in the log. Closes #209.
  • Fix bridge publishing failing when per_listener_settings was true. Closes #860.
  • Fix use_identity_as_username true not working. Closes #833.
  • Fix UNSUBACK messages not being logged. Closes #903.
  • Fix possible endian issue when reading the memory_limit option.
  • Fix building for libwebsockets < 1.6.
  • Fix accessor functions for username and client id when used in plugin auth check.


  • Fix some places where return codes were incorrect, including to the on_disconnect() callback. This has resulted in two new error codes, MOSQ_ERR_KEEPALIVE and MOSQ_ERR_LOOKUP.
  • Fix connection problems when mosquitto_loop_start() was called before mosquitto_connect_async(). Closes #848.


  • When compiled using WITH_TLS=no, the default port was incorrectly being set to -1. This has been fixed.
  • Fix compiling on Mac OS X <10.12. Closes #813 and #240.


  • Fixes for building on NetBSD. Closes #258.
  • Fixes for building on FreeBSD.
  • Add support for compiling with static libwebsockets library.

Updated Debian Repository Backend

The backend software for administering the Debian repository at has been migrated from reprepro to aptly. This has the benefit of allowing multiple versions of a package to remain in the repository.

For mosquitto, this now means that old versions of the Debian packages will remain available even after newer versions are published, and so you can depend on a particular version. The recommendation is always to use the latest version of course.

This change should be transparent to all current users, but there is the possibility that something is different between the two repository tools. If you do find a problem, please let us know.

The repository now has builds for versions 1.4.15 and 1.5.

Press release

I am pleased to announce that I am being paid to work on Mosquitto by Cedalo AG. I will be leaving my current job at the end of June this year, but have already started work for Cedalo on a limited basis.

The press release for this change is below:

New 1.5 release, MQTT 5.0 roadmap and commercial sponsor for Open-Source Eclipse Mosquitto MQTT Broker

Open-Source MQTT Broker Version 1.5 released – Estimate for availability of MQTT 5.0 compliant version – German based Cedalo AG becomes commercial sponsor for future Mosquitto Open Source development

A new version of the open source Eclipse Mosquitto MQTT broker is available on the Mosquitto website at Mosquitto version 1.5 brings a host of changes to the broker, including performance improvements and more flexible authentication and access control, as well as numerous bug fixes. The client library has added some helper functions to allow the creation of extremely simple MQTT clients.

The initiator and core developer of the Mosquitto project is now employed by the German based company Cedalo AG ( Cedalo has hired Roger Light to sponsor the further development of Mosquitto and to accelerate the public availability of a powerful MQTT broker. Cedalo is the creator of the end-user oriented IoT modelling tool “Streamsheets”.

With the new sponsorship the project is now able to accelerate the path towards new releases. The next version of Mosquitto will add support for MQTT version 5, which is the most substantial revision of the protocol since the first public specification was released. MQTT v5 adds error reporting, enhancements for scalability at the server side, features to help resource constrained clients, and extensible metadata - which is used amongst other things to introduce support for a request/response capability.

The MQTT v5 compliant release is planned for the end of August 2018.

Press Contact: Cedalo AG 79098 Freiburg, Schnewlinstr. 6

Kristian Raue Mail: