This is a bugfix release:


  • Prevent possible crash on client reconnect. Closes bug #1294108.
  • Don't accept zero length unsubscription strings (MQTT v3.1.1 fix)
  • Don't accept QoS 3 (MQTT v3.1.1 fix)
  • Don't disconnect clients immediately on HUP to give chance for all data to be read.
  • Reject invalid un/subscriptions e.g. foo/+bar #/bar.
  • Take more care not to disconnect clients that are sending large messages.

Client library

  • Fix socketpair code on the Mac.
  • Fix compilation for WITH_THREADING=no.
  • Break out of select() when calling mosquitto_loop_stop().
  • Reject invalid un/subscriptions e.g. foo/+bar #/bar.


  • Fix keepalive value on mosquitto_pub.
  • Fix possibility of mosquitto_pub not exiting after sending messages when using -l.