NAME

       mosquitto_sub - an mqtt version 3.1 client for subscribing to topics

SYNOPSIS

       mosquitto_sub [-c] [-d] [-h hostname] [-i client_id] [-I client id prefix] [-k keepalive time] [-p port
                     number] [-q message QoS] [--quiet] [-v] [ -u username [-P password] ] [ --will-topic topic
                     [--will-payload payload] [--will-qos qos] [--will-retain] ] -t message topic ...

DESCRIPTION

       mosquitto_sub  is  a simple mqtt version 3.1 client that will subscribe to a topic and print the messages
       that it receives.

OPTIONS

       -c, --disable-clean-session
              Disable the 'clean session' flag. This means that all of the subscriptions for the client will  be
              maintained  after it disconnects, along with subsequent QoS 1 and QoS 2 messages that arrive. When
              the client reconnects, it will receive all of the queued messages.

              If using this option, it is recommended that the client id is set manually with --id

       -d, --debug
              Enable debug messages.

       -h, --host
              Specify the host to connect to. Defaults to localhost.

       -i, --id
              The id to use for this client. If not given, defaults to mosquitto_sub_ appended with the  process
              id of the client. Cannot be used at the same time as the --id-prefix argument.

       -I, --id-prefix
              Provide  a prefix that the client id will be built from by appending the process id of the client.
              This is useful where the broker is using the clientid_prefixes option. Cannot be used at the  same
              time as the --id argument.

       -k, --keepalive
              The number of seconds between sending PING commands to the broker for the purposes of informing it
              we are still connected and functioning. Defaults to 60 seconds.

       -p, --port
              Connect to the port specified instead of the default 1883.

       -P, --pw
              Provide a password to be used for authenticating with the broker. Using this argument without also
              specifying  a  username  is  invalid. This requires a broker that supports MQTT v3.1. See also the
              --username option.

       -q, --qos
              Specify the quality of service desired for the incoming messages, from 0, 1 and 2. Defaults to  0.
              See mqtt(7) for more information on QoS.

              The QoS is identical for all topics subscribed to in a single instance of mosquitto_sub.

       --quiet
              If  this  argument  is  given, no runtime errors will be printed. This excludes any error messages
              given in case of invalid user input (e.g. using --port without a port).

       -t, --topic
              The mqtt topic to subscribe to. See mqtt(7) for more information on mqtt topics.

              This option may be repeated to subscribe to multiple topics.

       -u, --username
              Provide a username to be used for authenticating with the broker. This requires a broker that sup‐
              ports MQTT v3.1.  See also the --pw argument.

       -v, --verbose
              Print received messages verbosely. With this argument, messages will be  printed  as  "topic  pay‐
              load". When this argument is not given, the messages are printed as "payload".

       --will-payload
              Specify  a message that will be stored by the broker and sent out if this client disconnects unex‐
              pectedly. This must be used in conjunction with --will-topic.

       --will-qos
              The QoS to use for the Will. Defaults to 0. This must be used in conjunction with --will-topic.

       --will-retain
              If given, if the client disconnects unexpectedly the message sent out will be  treated  as  a  re‐
              tained message.  This must be used in conjunction with --will-topic.

       --will-topic
              The topic on which to send a Will, in the event that the client disconnects unexpectedly.

WILLS

       mosquitto_sub  can register a message with the broker that will be sent out if it disconnects unexpected‐
       ly. See mqtt(7) for more information.

       The minimum requirement for this is to use --will-topic to specify which topic the will  should  be  sent
       out on. This will result in a non-retained, zero length message with QoS 0.

       Use the --will-retain, --will-payload and --will-qos arguments to modify the other will parameters.

EXAMPLES

       Note  that  these  really  are examples - the subscriptions will work if you run them as shown, but there
       must be something publishing messages on those topics for you to receive anything.

       Subscribe to temperature information on localhost with QoS 1:

       • mosquitto_sub -t sensors/temperature -q 1

       Subscribe to hard drive temperature updates on multiple machines/hard drives. This expects  each  machine
       to be publishing its hard drive temperature to sensors/machines/HOSTNAME/temperature/HD_NAME.

       • mosquitto_sub -t sensors/machines/+/temperature/+

       Subscribe to all broker status messages:

       • mosquitto_sub -v -t \$SYS/#

BUGS

       mosquitto_sub bug information can be found at http://launchpad.net/mosquitto

SEE ALSO

       mqtt(7) mosquitto_pub(1) mosquitto(8) libmosquitto(3)

AUTHOR

       Roger Light <roger@atchoo.org>

                                                 5 February 2012                                mosquitto_sub(1)