This is a bugfix release: # Broker * 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`. # Clients * Fix keepalive value on mosquitto_pub. * Fix possibility of mosquitto_pub not exiting after sending messages when using -l.