This is a bugfix release.


  • The most recent version of libwebsockets (3.2.0) changed its behaviour and is not compatible with Mosquitto. This has been fixed for the next libwebsockets release. The 1.6.5 release refuses to compile with libwebsockets 3.2.0. All previous versions of Mosquitto that use websockets are affected by the change in behaviour.


  • Fix v5 DISCONNECT packets with remaining length == 2 being treated as a protocol error. Closes #1367.
  • Fix support for libwebsockets 3.x (excluding 3.2.0)
  • Fix slow websockets performance when sending large messages. Closes #1390.
  • Fix bridges potentially not connecting on Windows. Closes #478.
  • Fix clients authorised using use_identity_as_username or use_subject_as_username being disconnected on SIGHUP. Closes #1402.
  • Improve error messages in some situations when clients disconnect. Reduces the number of "Socket error on client X, disconnecting" messages.
  • Fix Will for v5 clients not being sent if will delay interval was greater than the session expiry interval. Closes #1401.
  • Fix CRL file not being reloaded on HUP. Closes #35.
  • Fix repeated "Error in poll" messages on Windows when only websockets listeners are defined. Closes #1391.

Client library

  • Fix reconnect backoff for the situation where connections are dropped rather than refused. Closes #737.
  • Fix missing locks on mosq->state. Closes #1374.


  • Improve details on global/per listener options in the mosquitto.conf man page. Closes #274.
  • Clarify behaviour when clients exceed the message_size_limit. Closes #448.
  • Improve documentation for max_inflight_bytes, max_inflight_messages, and max_queued_messages.


  • Fix missing function warnings on NetBSD.
  • Fix WITH_STATIC_LIBRARIES using CMake on Windows. Closes #1369.
  • Guard ssize_t definition on Windows. Closes #522.