mosquitto_sub(1) mosquitto_sub(1)
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 func-
tioning. 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 supports MQTT v3.1. See also the --pw
argument.
-v, --verbose
Print received messages verbosely. With this argument, messages will be printed as "topic payload". 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 unexpectedly. This must be used in con-
junction 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 retained 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 unexpectedly. See mqtt(7) for more informa-
tion.
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:
o 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.
o mosquitto_sub -t sensors/machines/+/temperature/+
Subscribe to all broker status messages:
o 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)