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<a name="mosquitto_sub"></a><div class="titlepage"></div>
<div class="refnamediv">
<p>mosquitto_sub — an MQTT version 3.1 client for subscribing to topics</p>
<div class="refsynopsisdiv">
<div class="cmdsynopsis"><p><code class="command">mosquitto_sub</code> [<code class="option">-1</code>] [<code class="option">-A</code> <em class="replaceable"><code>bind_address</code></em>] [<code class="option">-c</code>] [<code class="option">-d</code>] [<code class="option">-h</code> <em class="replaceable"><code>hostname</code></em>] [<code class="option">-i</code> <em class="replaceable"><code>client_id</code></em>] [<code class="option">-I</code> <em class="replaceable"><code>client id prefix</code></em>] [<code class="option">-k</code> <em class="replaceable"><code>keepalive time</code></em>] [<code class="option">-p</code> <em class="replaceable"><code>port number</code></em>] [<code class="option">-q</code> <em class="replaceable"><code>message QoS</code></em>] [<code class="option">-R</code>] [<code class="option">-S</code>] [<code class="option">-N</code>] [<code class="option">--quiet</code>] [<code class="option">-v</code>] [
[<code class="option">-u</code> <em class="replaceable"><code>username</code></em>]
[<code class="option">-P</code> <em class="replaceable"><code>password</code></em>]
] [
<code class="option">--will-topic</code> <em class="replaceable"><code>topic</code></em>
[<code class="option">--will-payload</code> <em class="replaceable"><code>payload</code></em>]
[<code class="option">--will-qos</code> <em class="replaceable"><code>qos</code></em>]
[<code class="option">--will-retain</code>]
] [[
{ <code class="option">--cafile</code> <em class="replaceable"><code>file</code></em> | <code class="option">--capath</code> <em class="replaceable"><code>dir</code></em> }
[<code class="option">--cert</code> <em class="replaceable"><code>file</code></em>]
[<code class="option">--key</code> <em class="replaceable"><code>file</code></em>]
[<code class="option">--tls-version</code> <em class="replaceable"><code>version</code></em>]
[<code class="option">--insecure</code>]
] | [
<code class="option">--psk</code> <em class="replaceable"><code>hex-key</code></em>
<code class="option">--psk-identity</code> <em class="replaceable"><code>identity</code></em>
[<code class="option">--tls-version</code> <em class="replaceable"><code>version</code></em>]
]] [<code class="option">--proxy</code> <em class="replaceable"><code>socks-url</code></em>] [<code class="option">-V</code> <em class="replaceable"><code>protocol-version</code></em>] [<code class="option">-T</code> <em class="replaceable"><code>filter-out</code></em>...] <code class="option">-t</code> <em class="replaceable"><code>message-topic</code></em>... </p></div>
<div class="cmdsynopsis"><p><code class="command">mosquitto_sub</code> [<code class="option">--help</code>] </p></div>
<div class="refsect1">
<a name="idp49139792"></a><h2>Description</h2>
<p><span class="command"><strong>mosquitto_sub</strong></span> is a simple MQTT version 3.1
client that will subscribe to a topic and print the messages that it
<div class="refsect1">
<a name="idp49141328"></a><h2>Options</h2>
<p>The options below may be given on the command line, but may also
be placed in a config file located at
<code class="option">$XDG_CONFIG_HOME/mosquitto_sub</code> or
<code class="option">$HOME/.config/mosquitto_sub</code> with one pair of
<code class="option">-option <em class="replaceable"><code>value</code></em></code>
per line. The values in the config file will be used as defaults
and can be overridden by using the command line. The exceptions to
this are <code class="option">-t</code> and <code class="option">-T</code>, which if
given in the config file will not be overridden. Note also that
currently some options cannot be negated, e.g.
<code class="option">-S</code>. Config file lines that have a
<code class="option">#</code> as the first character are treated as comments
and not processed any further.</p>
<div class="variablelist"><dl class="variablelist">
<dt><span class="term"><code class="option">-1</code></span></dt>
<p>Disconnect and exit the program immediately after the
first message is received. This may be useful in shell
scripts where on a single status value is required, for
<p>Combine with <code class="option">-R</code> to print only the
first fresh message (i.e. that does not have the
retained flag set), or with <code class="option">-T</code> to
filter which topics are processed.</p>
<dt><span class="term"><code class="option">-A</code></span></dt>
<dd><p>Bind the outgoing connection to a local ip
address/hostname. Use this argument if you need to
restrict network communication to a particular
<span class="term"><code class="option">-c</code>, </span><span class="term"><code class="option">--disable-clean-session</code></span>
<p>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.</p>
<p>If using this option, it is recommended that the
client id is set manually with <code class="option">--id</code></p>
<dt><span class="term"><code class="option">--cafile</code></span></dt>
<p>Define the path to a file containing PEM encoded CA
certificates that are trusted. Used to enable SSL
<p>See also <code class="option">--capath</code></p>
<dt><span class="term"><code class="option">--capath</code></span></dt>
<p>Define the path to a directory containing PEM encoded CA
certificates that are trusted. Used to enable SSL
<p>For <code class="option">--capath</code> to work correctly, the
certificate files must have ".crt" as the file ending
and you must run "c_rehash &lt;path to capath&gt;" each
time you add/remove a certificate.</p>
<p>See also <code class="option">--cafile</code></p>
<dt><span class="term"><code class="option">--cert</code></span></dt>
<p>Define the path to a file containing a PEM encoded
certificate for this client, if required by the
<p>See also <code class="option">--key</code>.</p>
<dt><span class="term"><code class="option">--ciphers</code></span></dt>
<dd><p>An openssl compatible list of TLS ciphers to support
in the client. See
<span class="citerefentry"><span class="refentrytitle">ciphers</span>(1)</span>
for more information.</p></dd>
<span class="term"><code class="option">-d</code>, </span><span class="term"><code class="option">--debug</code></span>
<dd><p>Enable debug messages.</p></dd>
<dt><span class="term"><code class="option">--help</code></span></dt>
<dd><p>Display usage information.</p></dd>
<span class="term"><code class="option">-h</code>, </span><span class="term"><code class="option">--host</code></span>
<dd><p>Specify the host to connect to. Defaults to localhost.</p></dd>
<span class="term"><code class="option">-i</code>, </span><span class="term"><code class="option">--id</code></span>
<dd><p>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
<code class="option">--id-prefix</code> argument.</p></dd>
<span class="term"><code class="option">-I</code>, </span><span class="term"><code class="option">--id-prefix</code></span>
<dd><p>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
<code class="option">--id</code> argument.</p></dd>
<dt><span class="term"><code class="option">--insecure</code></span></dt>
<dd><p>When using certificate based encryption, this option
disables verification of the server hostname in the
server certificate. This can be useful when testing
initial server configurations but makes it possible for
a malicious third party to impersonate your server
through DNS spoofing, for example. Use this option in
testing <span class="emphasis"><em>only</em></span>. If you need to
resort to using this option in a production
environment, your setup is at fault and there is no
point using encryption.</p></dd>
<span class="term"><code class="option">-k</code>, </span><span class="term"><code class="option">--keepalive</code></span>
<dd><p>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></dd>
<dt><span class="term"><code class="option">--key</code></span></dt>
<p>Define the path to a file containing a PEM encoded
private key for this client, if required by the
<p>See also <code class="option">--cert</code>.</p>
<dt><span class="term"><code class="option">-N</code></span></dt>
<dd><p>Do not append an end of line character to the payload
when printing. This allows streaming of payload data
from multiple messages directly to another application
unmodified. Only really makes sense when not using
<code class="option">-v</code>.</p></dd>
<span class="term"><code class="option">-p</code>, </span><span class="term"><code class="option">--port</code></span>
<dd><p>Connect to the port specified instead of the default 1883.</p></dd>
<span class="term"><code class="option">-P</code>, </span><span class="term"><code class="option">--pw</code></span>
<dd><p>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 <code class="option">--username</code> option.</p></dd>
<dt><span class="term"><code class="option">--proxy</code></span></dt>
<p>Specify a SOCKS5 proxy to connect through. "None" and
"username" authentication types are supported. The
<code class="option">socks-url</code> must be of the form
<code class="option">socks5h://[username[:password]@]host[:port]</code>.
The protocol prefix <code class="option">socks5h</code> means that
hostnames are resolved by the proxy. The symbols %25,
%3A and %40 are URL decoded into %, : and @
respectively, if present in the username or
<p>If username is not given, then no authentication is
attempted. If the port is not given, then the default
of 1080 is used.</p>
<p>More SOCKS versions may be available in the future,
depending on demand, and will use different protocol
prefixes as described in <span class="citerefentry"><span class="refentrytitle">curl</span>(1)</span>.</p>
<dt><span class="term"><code class="option">--psk</code></span></dt>
<dd><p>Provide the hexadecimal (no leading 0x)
pre-shared-key matching the one used on the broker to
use TLS-PSK encryption support.
<code class="option">--psk-identity</code> must also be provided
to enable TLS-PSK.</p></dd>
<dt><span class="term"><code class="option">--psk-identity</code></span></dt>
<dd><p>The client identity to use with TLS-PSK support. This
may be used instead of a username if the broker is
configured to do so.</p></dd>
<span class="term"><code class="option">-q</code>, </span><span class="term"><code class="option">--qos</code></span>
<p>Specify the quality of service desired for the
incoming messages, from 0, 1 and 2. Defaults to 0. See
<span class="citerefentry"><span class="refentrytitle">mqtt</span>(7)</span>
for more information on QoS.</p>
<p>The QoS is identical for all topics subscribed to in
a single instance of mosquitto_sub.</p>
<dt><span class="term"><code class="option">--quiet</code></span></dt>
<dd><p>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 <code class="option">--port</code> without a
<dt><span class="term"><code class="option">-R</code></span></dt>
<dd><p>If this argument is given, messages that are received
that have the retain bit set will not be printed.
Messages with retain set are "stale", in that it is not
known when they were originally published. When
subscribing to a wildcard topic there may be a large
number of retained messages. This argument suppresses
their display.</p></dd>
<dt><span class="term"><code class="option">-S</code></span></dt>
<dd><p>Use SRV lookups to determine which host to connect
to. Performs lookups to
<code class="option">_mqtt._tcp.&lt;host&gt;</code> when used in
conjunction with <code class="option">-h</code>, otherwise uses
<code class="option">_mqtt._tcp.&lt;local dns
<span class="term"><code class="option">-t</code>, </span><span class="term"><code class="option">--topic</code></span>
<p>The MQTT topic to subscribe to. See
<span class="citerefentry"><span class="refentrytitle">mqtt</span>(7)</span>
for more information on MQTT topics.</p>
<p>This option may be repeated to subscribe to multiple topics.</p>
<span class="term"><code class="option">-T</code>, </span><span class="term"><code class="option">--filter-out</code></span>
<p>Suppress printing of topics that match the filter.
This allows subscribing to a wildcard topic and only
printing a partial set of the wildcard
<p>For example, subscribe to the BBC tree, but suppress output from Radio 3:</p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem" style="list-style-type: circle"><p>mosquitto_sub <code class="literal">-t</code>
bbc/# <code class="literal">-T</code>
<p>This option may be repeated to filter out multiple
topics or topic trees.</p>
<dt><span class="term"><code class="option">--tls-version</code></span></dt>
<dd><p>Choose which TLS protocol version to use when
communicating with the broker. Valid options are
<code class="option">tlsv1.2</code>, <code class="option">tlsv1.1</code> and
<code class="option">tlsv1</code>. The default value is
<code class="option">tlsv1.2</code>. If the installed version of
openssl is too old, only <code class="option">tlsv1</code> will be
available. Must match the protocol version used by the
<span class="term"><code class="option">-u</code>, </span><span class="term"><code class="option">--username</code></span>
<dd><p>Provide a username to be used for authenticating with
the broker. This requires a broker that supports MQTT v3.1.
See also the <code class="option">--pw</code> argument.</p></dd>
<span class="term"><code class="option">-v</code>, </span><span class="term"><code class="option">--verbose</code></span>
<dd><p>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
<span class="term"><code class="option">-V</code>, </span><span class="term"><code class="option">--protocol-version</code></span>
<dd><p>Specify which version of the MQTT protocol should be
used when connecting to the rmeote broker. Can be
<code class="option">mqttv31</code> or <code class="option">mqttv311</code>.
Defaults to <code class="option">mqttv31</code>.</p></dd>
<dt><span class="term"><code class="option">--will-payload</code></span></dt>
<dd><p>Specify a message that will be stored by the broker
and sent out if this client disconnects unexpectedly. This
must be used in conjunction with <code class="option">--will-topic</code>.</p></dd>
<dt><span class="term"><code class="option">--will-qos</code></span></dt>
<dd><p>The QoS to use for the Will. Defaults to 0. This must
be used in conjunction with <code class="option">--will-topic</code>.</p></dd>
<dt><span class="term"><code class="option">--will-retain</code></span></dt>
<dd><p>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 <code class="option">--will-topic</code>.</p></dd>
<dt><span class="term"><code class="option">--will-topic</code></span></dt>
<dd><p>The topic on which to send a Will, in the event that
the client disconnects unexpectedly.</p></dd>
<div class="refsect1">
<a name="idp49240288"></a><h2>Wills</h2>
<p>mosquitto_sub can register a message with the broker that will be
sent out if it disconnects unexpectedly. See
<span class="citerefentry"><span class="refentrytitle">mqtt</span>(7)</span>
for more information.</p>
<p>The minimum requirement for this is to use <code class="option">--will-topic</code> to
specify which topic the will should be sent out on. This will result in
a non-retained, zero length message with QoS 0.</p>
<p>Use the <code class="option">--will-retain</code>, <code class="option">--will-payload</code> and <code class="option">--will-qos</code> arguments to
modify the other will parameters.</p>
<div class="refsect1">
<a name="idp49244784"></a><h2>Examples</h2>
<p>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.</p>
<p>Subscribe to temperature information on localhost with QoS 1:</p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem" style="list-style-type: circle"><p>mosquitto_sub <code class="literal">-t</code> sensors/temperature <code class="literal">-q</code> 1</p></li></ul></div>
<p>Subscribe to hard drive temperature updates on multiple
machines/hard drives. This expects each machine to be publishing its
hard drive temperature to
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem" style="list-style-type: circle"><p>mosquitto_sub <code class="literal">-t</code> sensors/machines/+/temperature/+</p></li></ul></div>
<p>Subscribe to all broker status messages:</p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem" style="list-style-type: circle"><p>mosquitto_sub <code class="literal">-v</code> <code class="literal">-t</code> \$SYS/#</p></li></ul></div>
<div class="refsect1">
<a name="idp49252912"></a><h2>Files</h2>
<div class="variablelist"><dl class="variablelist">
<span class="term"><code class="filename">$XDG_CONFIG_HOME/mosquitto_sub</code>, </span><span class="term"><code class="filename">$HOME/.config/mosquitto_sub</code></span>
<dd><p>Configuration file for default options.</p></dd>
<div class="refsect1">
<a name="idp49256384"></a><h2>Bugs</h2>
<p><span class="command"><strong>mosquitto_sub</strong></span> bug information can be found at
<code class="uri"></code></p>
<div class="refsect1">
<a name="idp49258416"></a><h2>See Also</h2>
<span class="simplelist">
<span class="citerefentry"><span class="refentrytitle"><a class="link" href="mqtt-7.php" target="_top">mqtt</a></span>(7)</span>
<span class="citerefentry"><span class="refentrytitle"><a class="link" href="mosquitto_pub-1.php" target="_top">mosquitto_pub</a></span>(1)</span>
<span class="citerefentry"><span class="refentrytitle"><a class="link" href="mosquitto-8.php" target="_top">mosquitto</a></span>(8)</span>
<span class="citerefentry"><span class="refentrytitle"><a class="link" href="libmosquitto-3.php" target="_top">libmosquitto</a></span>(3)</span>
<span class="citerefentry"><span class="refentrytitle"><a class="link" href="mosquitto-tls-7.php" target="_top">mosquitto-tls</a></span>(7)</span>
<div class="refsect1">
<a name="idp49269472"></a><h2>Author</h2>
<p>Roger Light <code class="email">&lt;<a class="email" href=""></a>&gt;</code></p>
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