MOSQUITTO_SUB(1)

📦

version 2.1.2 · 13 versions

🌸 MOSQUITTO_SUB 💅 — the `mosquitto_sub(1)` page, bestie edition 🌸

ok so this is the manual for mosquitto_sub, from the Commands section, and it's literally about to be your new fave little MQTT gremlin. buckle up 🎀

✨ NAME ✨

mosquitto_sub — an MQTT version 5/3.1.1/3.1 client for subscribing to topics 🦋

⭐ SYNOPSIS ⭐

mosquitto_sub [options] {-t message-topic... | -U unsubscribe-topic...}

options:
         [auth-options] [connection-options] [misc-options]
         [mqtt-options] [output-options] [tls-certificate-options |
         tls-psk-options]

auth-options:
              [-u username] [-P password]

connection-options:
                    {[-h hostname] [--unix socket path] [-p port-number]
                    | -L URL }
                    [-A bind-address] [--nodelay] [-S] [--ws]
                    [--proxy socks-url]

misc-options:
              [-E] [-o config-file] [-W message-processing-timeout]

mqtt-options:
              [-c] [-D command identifier value] [-i client-id]
              [-I client-id-prefix] [-k keepalive-time] [-q message-QoS]
              [--retain-as-published]
              [--retain-handling always | new | never]
              [-V protocol-version] [-x session-expiry-interval]
              [--will-topic topic [--will-payload payload] [--will-qos qos] [--will-retain]]

output-options:
                [-d] [-C msg-count] [--message-rate] [-N] [--pretty]
                [--random-filter chance] [--remove-retained] [-R |
                --retained-only] [--quiet] [-T filter-out...] [-v] [-w |
                --watch]

tls-certificate-options:
                         [--no-tls]
                         {--cafile file | --capath dir}
                         [--tls-use-os-certs]
                         [--cert file] [--key file]
                         [--ciphers ciphers] [--insecure]
                         [--tls-alpn protocol] [--tls-keylog file]
                         [--tls-version version]
                         [--tls-engine engine]
                         [--keyform {pem | engine}]
                         [--tls-engine-kpass-sha1 kpass-sha1]

tls-psk-options:
                 --psk hex-key --psk-identity identity
                 [--ciphers ciphers] [--tls-version version]

mosquitto_sub [--help]

like yes that's a lot of brackets. it's giving "choose your own adventure" and honestly? iconic. 👑

💖 DESCRIPTION 💖

mosquitto_sub is a simple MQTT version 5/3.1.1 client that will subscribe to topics and print the messages that it receives. that's the whole job. it subscribes, it prints, it minds its business. 🫶

but wait — it does more than just subscribe to topics, ok? mosquitto_sub can also filter out received messages so they are not printed (peep the -T option) or unsubscribe from topics (peep the -U option). Unsubscribing from topics is useful for clients connecting with clean session set to false. yes bestie, sometimes you gotta un-subscribe. self care. 💅

🔐 ENCRYPTED CONNECTIONS 🔐

This client supports TLS encrypted connections. and like, it is strongly recommended that you use an encrypted connection for anything more than the most basic setup. no cap, do not be out here raw-dogging your network traffic. 😭

To enable TLS connections when using x509 certificates, one of either --cafile or --capath can be provided as an option.

Alternatively, if the -p 8883 option is used then the OS provided certificates will be loaded and neither --cafile or --capath are needed. convenient much? ✨

To enable TLS connections when using TLS-PSK, you must use the --psk and the --psk-identity options. both of them. it's a pair. they're a matching set, like me and my emotional support terminal. 🎀

🌈 OPTIONS 🌈

There are three ways to provide options to mosquitto_sub: the default config file, a specified config file, or options on the command line. three whole vibes. pick one. 💫

🍓 Default Config File

The default config file is located at $XDG_CONFIG_HOME/mosquitto_sub or $HOME/.config/mosquitto_sub on POSIX systems, or %USERPROFILE%\mosquitto_sub on Windows.

The contents of the config file should consist of options, one per line in the format: -option value. If options are also specified on the command line, those options will override the same options set in the config file. command line stays winning, periodt. 👑

The exceptions to this are the message type options, of which only one can be specified. Note also that currently some options cannot be negated, e.g. -S. TLS encryption options can be negated with the --no-tls option.

Config file lines that have a # as the first character are treated as comments and not processed any further. so # is your girl for leaving little notes to yourself. ✨

It is suggested that config files are primarily used for authentication purposes. Use of a config file allows you to authenticate without the need to show the username and password on the command line. which is lowkey the whole point — no one needs your password living in your shell history forever, bestie. 🙈

🦋 Config File

Available from version 2.1. ok so this is the newer flex.

A config file can be specified on the command line using -o config-file. If the -o option is used, the default config file will not be loaded. it's one or the other, no sharing. 💅

The format is the same as for the default config file.

👑 The options

-A — Bind the outgoing connection to a local ip address/hostname. Use this argument if you need to restrict network communication to a particular interface. it's giving "I only talk through this door" energy. 🚪
-c, --disable-clean-session — Disable 'clean session' / enable persistent client mode. When this argument is used, the broker will be instructed not to clean existing sessions for the same client id when the client connects, and sessions will never expire when the client disconnects. MQTT v5 clients can change their session expiry interval with the -x argument.

When a session is persisted on the broker, 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 and does not clean the session, it will receive all of the queued messages. it's like leaving your read receipts on but for messages. 📬

If using this option, the client id must be set manually with --id. no auto-generated shenanigans here, bestie — you have to name your child yourself. 😤

--cafile — Define the path to a file containing PEM encoded CA certificates that are trusted. Used to enable SSL communication.

See also --tls-engine.

-L, --url — Specify specify user, password, hostname, port and topic at once as a URL. The URL must be in the form: mqtt(s)://[username[:password]@]host[:port]/topic or ws(s)://[username[:password]@]host[:port]/path

Depending on the scheme, the port will default to different values. mqtt:// — 1883, mqtts:// — 8883, ws:// — 80, wss:// — 443. one URL to rule them all, no cap. 🔥

--message-rate — ok so this one's from version 2.1 ✨ Instead of actually printing the messages you receive, it prints a count of how many messages came in, once every second. Little vibe-check tally, love that. Heads up though: any other options that mess with output formatting are not valid while this is active, so don't try it 💅
-N — do not append an end of line character to the payload when printing. This is the streaming bestie option — it lets you pipe payload data from multiple messages straight into another application unmodified. Lowkey only really makes sense when you're not using -v, iykyk.
--nodelay — disables Nagle's algorithm on the socket 🔥 This means the latency of sent messages goes down, which is especially noticeable for small, reasonably infrequent messages. Trade-off: using this may result in more packets being sent than would normally be necessary. Slay, but at a cost.
--no-tls — available from version 2.1. Disables all use of TLS encryption 🚫🔒 Super useful if you've got TLS options sitting in a configuration file but you wanna switch them off. It also stops the automatic use of TLS when connecting to port 8883.
-o config-file — available from version 2.1. Loads options from a config file 📄 See the Default Config File and Config File sections at the start of the Options section for the deets.
-p, --port — connect to the port you specify. If you don't give one, the default is 1883 for plain MQTT or 8883 for MQTT over TLS 💫
-P, --pw — gives a password to use when authenticating with the broker 🔑 Using this argument without also specifying a username is invalid when using MQTT v3.1 or v3.1.1. See also the --username option.
--pretty — when you're using the JSON output format %j or %J, the default is to print in an unformatted fashion. Throw --pretty in there and messages print in a prettier, more human readable format 🎀 It's giving organized.
--proxy — specify a SOCKS5 proxy to connect through. "None" and "username" authentication types are supported. The socks-url must be of the form:

socks5h://[username[:password]@]host[:port]

The protocol prefix socks5h 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 password.

If username is not given, then no authentication is attempted. If the port is not given, then the default of 1080 is used.

If the host is given as an IPv6 address, it must be enclosed in square brackets, e.g. socks5h://[::1]:1080. Note that square brackets have special meaning in some shells, so the proxy url may need quoting in double or single quotes 🙈

More SOCKS versions may be available in the future, depending on demand, and will use different protocol prefixes as described in curl(1).

--psk — provide the hexadecimal (no leading 0x) pre-shared-key matching the one used on the broker, to use TLS-PSK encryption support. --psk-identity must also be provided to enable TLS-PSK 🔐
--psk-identity — 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 💜
-q, --qos — specify the quality of service you want for the incoming messages, from 0, 1 and 2. Defaults to 0. See mqtt(7) for more info on QoS. This QoS applies to all topics subscribed to in a single instance of this client 👑
--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). Those still show up, bestie.
-R — if this argument is given, messages received that have the retain bit set will not be printed. Messages with retain set are "stale", in that it's not known when they were originally published. When subscribing to a wildcard topic there may be a large number of retained messages, and this argument suppresses their display. See also --retain-handling 💀
--random-filter — this option reduces the proportion of messages that mosquitto_sub prints. The default behaviour is to print all incoming messages. Setting the chance to a floating point value between 0.1 and 100.0 will ensure that on average that percentage of messages will be printed 🎲
--remove-retained — if this argument is given, then when mosquitto_sub receives a message with the retained bit set, it will send a message to the broker to clear that retained message 🧹 This applies to all received messages except those that are filtered out by the -T option. This option still takes effect even if -R is used. See also the --retain-as-published and --retained-only options.

Example 1. Remove all retained messages on the server, assuming we have access to do so, and then exit:

mosquitto_sub -t '#' --remove-retained --retained-only

Example 2. Remove a whole tree, with the exception of a single topic:

mosquitto_sub -t 'bbc/#' -T bbc/bbc1 --remove-retained

--retained-only — if this argument is given, only messages received that have the retain bit set will be printed. Messages with retain set are "stale", in that it's not known when they were originally published. With this argument in use, the receipt of the first non-stale message will cause the client to exit 👋 See also the --retain-as-published option.
--retain-as-published — if this argument is given, the subscriptions will have the "retain as published" option set. This means the retain flag on an incoming message will be exactly as set by the publishing client, rather than indicating whether the message is fresh/stale ✨

This option is not valid for MQTT v3.1/v3.1.1 clients. Periodt.

--retain-handling always | new | never — available from version 2.1. Use this option to control the retain handling option when making a subscription. This controls under what circumstances an existing retained message is sent to the client when the subscription is made 🎀
- always — always deliver retained messages
- new — deliver retained messages the first time a subscription is made, but not on subsequent subscriptions. This is useful for the case where you have a long running client using a non-clean session. If the connection is dropped briefly, when the client reconnects you will not receive the retained messages again 💡
- never — never deliver retained messages
-S — use SRV lookups to determine which host to connect to. Performs lookups to _mqtt._tcp.<host> when used in conjunction with -h, otherwise uses _mqtt._tcp.<local dns domain> 🌈
-t, --topic — the MQTT topic to subscribe to. See mqtt(7) for more info on MQTT topics. This option may be repeated to subscribe to multiple topics 👑 (yes, repeat it, go off)
-T, --filter-out — suppress printing of topics that match the filter. This lets you subscribe to a wildcard topic and only print a partial set of the wildcard hierarchy 🦋 For example, subscribe to the BBC tree, but suppress output from Radio 3:
- mosquitto_sub -t bbc/# -T bbc/radio3

This option may be repeated to filter out multiple topics or topic trees.

--tls-alpn — provide a protocol to use when connecting to a broker that has multiple protocols available on a single port, e.g. MQTT and WebSockets 💅
--tls-engine — a valid openssl engine id. These can be listed with the openssl engine command. See also --keyform.
--tls-engine-kpass-sha1 — SHA1 of the private key password when using a TLS engine. Some TLS engines such as the TPM engine may require the use of a password in order to be accessed. This option allows a hex encoded SHA1 hash of the password to the engine directly, instead of the user being prompted for the password 🔐 See also --tls-engine.
--tls-keylog file — available from version 2.1. Log TLS connection information to file. This option allows tools such as tcpdump, wireshark and mqttshark to decrypt TLS traffic and inspect the MQTT traffic 🔍 In Wireshark this can be done by setting the (Pre)-Master-Secret log filename option for the Transport Layer Security protocol.

Debugging only, bestie. It must not be used in production. Like, seriously. 😭

--tls-use-os-certs — if used, this will load and trust the OS provided CA certificates 🌸 This can be used in conjunction with --cafile and --capath and can be used on its own to enable TLS mode. This will be set by default if -L mqtts://... is used, or if port is 8883 and no other certificate options are used.
--tls-version — choose which TLS protocol version to use when communicating with the broker. Valid options are tlsv1.3 and tlsv1.2. The default value is tlsv1.2. Must match the protocol version used by the broker ⭐
-u, --username — provide a username to be used for authenticating with the broker 💜 See also the --pw argument.
--unix — connect to a broker through a local unix domain socket instead of a TCP socket 🧚 This is a replacement for -h and -L. For example:

mosquitto_pub --unix /tmp/mosquitto.sock ...

See the socket_domain option in mosquitto.conf(5) to configure Mosquitto to listen on a unix socket.

-U, --unsubscribe — a topic that will be unsubscribed from. This may be used on its own or in conjunction with the --topic option and only makes sense when used in conjunction with --clean-session. If used with --topic then subscriptions will be processed before unsubscriptions.

Note that it's only possible to unsubscribe from subscriptions that have previously been made. It is not possible to punch holes in wildcard subscriptions 💀 For example, subscribing to sensors/# and then unsubscribing from sensors/+/temperature as shown below will still result in messages matching the sensors/+/temperature being delivered to the client.

mosquitto_sub -t sensors/# -U sensors/+/temperature -v

Note also that because retained messages are published by the broker on receipt of a SUBSCRIBE command, subscribing and unsubscribing to the same topic may result in messages being received at the client 🙈

This option may be repeated to unsubscribe from multiple topics.

-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". See also -F ✨
-V, --protocol-version — tells the client which MQTT protocol version to use when it connects to the remote broker. You can pass 5, 311, 31, or the extra-readable mqttv5, mqttv311, or mqttv31. Defaults to 311, bestie.
-W — give it a timeout as an integer number of seconds. The client stops processing messages and disconnects after that many seconds have passed. The clock starts right after the client connects to the broker. ⏱️
-w, --watch — available from version 2.1. Messages get printed on a fixed line number based on the topic and the order in which topics are received. Super useful for monitoring multiple topics that have single-line payloads. Unexpected behaviour will occur if there are more topics than lines in the terminal, or if the payload takes up more than a single line. You can use this together with other output options, e.g. -F. Requires ANSI escape code support in the terminal. 👀
--will-payload — specify a message that the broker will store and send out if this client disconnects unexpectedly. 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, and the client disconnects unexpectedly, the message that gets 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.
--ws — connect using WebSockets instead of plain TCP. 🕸️
-x — set the session-expiry-interval property on the CONNECT packet. If you use this option, the client will be set to be an MQTT v5 client. Set to 0-4294967294 to specify the session will expire in that many seconds after the client disconnects, or use -1, 4294967295, or ∞ for a session that does not expire. Defaults to -1 if -c is also given, or 0 if -c is not given. If the session is set to never expire, either with -x or -c, then a client id must be provided. 🫶

🌸 OUTPUT FORMAT 🌸

There are three ways of formatting the printed output. In all cases a new-line character is appended for each message received unless the -N argument is given.

Payload-only is the default output format and will print the payload exactly as it is received.

Verbose mode is activated with -v and prints the message topic and the payload, separated by a space.

The final option is formatted output, which lets the user define a custom output format. The behaviour is controlled with the -F format-string option. The format string is a free text string where interpreted sequences are replaced by different parameters. The available interpreted sequences are described below.

Three characters are used to start an interpreted sequence: %, @ and \. Sequences starting with % are either parameters related to the MQTT message being printed, or helper sequences to avoid the need to type long date format strings for example. Sequences starting with @ are passed to the strftime(3) function (with the @ replaced with a % — note that only the character immediately after the @ is passed to strftime). This allows the construction of a wide variety of time-based outputs. The output options for strftime vary from platform to platform, so please check what is available for your platform. One extension to strftime is provided, which is @N, and it can be used to obtain the number of nanoseconds passed in the current second. The resolution of this option varies depending on the platform. The final sequence character is \, which is used to input some characters that would otherwise be difficult to enter. ✨

✨ Flag characters ✨

The parameters %A, %C, %d, %E, %F, %f, %I, %l, %m, %p, %R, %S, %t, %x, and %X can have optional flags immediately after the % character.

0 — the value should be zero padded. This applies to the parameters %A, %E, %d, %F, %f, %l, %m, %S, %X, and %x. It will be ignored for other parameters. If used with the - flag, the 0 flag will be ignored.
- — the value will be left aligned to the field width, padded with blanks. The default is right alignment, with either 0 or blank padding.

🌈 Field width 🌈

Some of the MQTT-related parameters can be formatted with an option to set their field width in a similar way to regular printf style formats, i.e. this sets the minimum width when printing this parameter. If the output length is smaller than this width, the field will be padded to meet this width. This applies to the options %A, %C, %d, %E, %F, %f, %I, %l, %m, %p, %R, %S, %t, %x, %X.

For example %10t would set the minimum topic field width to 10 characters.

💅 Maximum width 💅

Some of the MQTT-related parameters can be formatted with an option to set a maximum field width in a similar way to regular printf style formats, for example %.20t for a maximum width of 20. This applies to the options %C, %I, %R, %t.

For example %10.10t would set the minimum topic field width to 10 characters, and the maximum topic width to 10 characters, i.e. the field will always be exactly 10 characters long. Periodt.

🧚 Hexadecimal binary field width 🧚

The %x and %X parameters output the payload as a single hexadecimal string by default. It is also possible to split the hexadecimal payload into fields by a chosen length of nibbles. For example, %.2x would split the payload into two-nibble or one-byte values, separated by spaces, and might produce an output of 18 83.

The separator character is a space by default, but can be changed to one of these characters:

!"#$&'()*+,-./:;<=>?@[\]^_`{|}~

by adding that character after the binary field width. For example, %.2:x might produce an output of 18:83.

🍓 Floating point number printing consideration 🍓

The output format supports only the IEEE 754 floating point standard as described in Annex F of ISO/IEC 9899:1999. Don't try to use %f or %d if the platform of the publisher uses a different floating point representation standard than IEEE 754, or you will get invalid data. If you are unsure what floating representation your platform is using, then it is most likely IEEE 754. If you get malformed or unexpected values, check if the floating point number in the payload from the publisher is encoded in IEEE 754.

If you want to print floats, make sure you only subscribe to topics that send only IEEE 754 formatted floats. The processing is very strict about floats, and if anything that is not a float is received, an error message will be printed. 😭

%% — a literal %.
%A — the MQTT v5 topic-alias property, if present.
%C — the MQTT v5 content-type property, if present.
%D — the MQTT v5 correlation-data property, if present. Note that this property is specified as binary data, so it may produce non-printable characters.
%d — the payload treated as an 8-byte IEEE 754 float (double).
%E — the MQTT v5 message-expiry-interval property, if present.
%F — the MQTT v5 payload-format-indicator property, if present.
%f — the payload treated as a 4-byte IEEE 754 float.
%l — the length of the payload in bytes.
%m — the message id (only relevant for messages with QoS>0).
%P — the MQTT v5 user-property property, if present. This will be printed in the form key:value. It is possible for any number of user properties to be attached to a message, and to have duplicate keys.
%p — the payload raw bytes (may produce non-printable characters depending on the payload).
%q — the message QoS.
%R — the MQTT v5 response-topic property, if present.
%r — the retained flag for the message.
%S — the MQTT v5 subscription-identifier property, if present.
%t — the message topic.
%x — the payload with each byte as a hexadecimal number (lower case).
%X — the payload with each byte as a hexadecimal number (upper case).

👑 Helpers 👑

%I — ISO-8601 format date and time, e.g. 2016-08-10T09:47:38+0100.
%j — JSON output of message parameters and timestamp, with a quoted and escaped payload. For example:

{"tst":"2020-05-06T22:12:00.000000+0100","topic":"greeting","qos":0,"retain":0,"payload":"hello world"}

%J — JSON output of message parameters and timestamp, with a non-quoted and non-escaped payload — this means the payload must itself be valid JSON. For example:

{"tst":"2020-05-06T22:12:00.000000+0100","topic":"foo","qos":0,"retain":0,"payload":{"temperature":27.0,"humidity":57}}

If the payload is not valid JSON, then the error message Error: Message payload is not valid JSON on topic <topic> will be printed to stderr. 🙈

%U — Unix timestamp with nanoseconds, e.g. 1470818943.786368637.

@@ — a literal @.
@X — pass the character represented by X to the strftime function as %X. The options supported are platform dependent.
@N — the number of nanoseconds that have passed in the current second, with varying timing resolution depending on platform.

💜 Escape characters 💜

\\ — a literal \.
\0 — a null character. Can be used to separate different parameters that may contain spaces (e.g. topic, payload) so that processing with tools such as xargs(1) is easier.
\a — alert/bell.
\e — the escape sequence, which can be used with ANSI colour codes to provide coloured output for example.
\n — end of line.
\r — carriage return.
\t — horizontal tab.
\v — vertical tab.

💀 WILLS 💀

The client can register a message with the broker that will be sent out if it disconnects unexpectedly. 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.

🌈 PROPERTIES 🌈

Okay bestie, so the -D / --property option is literally the glow-up option — it lets you add properties to the different stages of the mosquitto_sub run. Each stage only accepts its own little curated set, and here's the full guest list 💅

✨ Connect ✨

authentication-data (binary data — note: treated as a string)
authentication-method (UTF-8 string pair)
maximum-packet-size (32-bit unsigned integer)
receive-maximum (16-bit unsigned integer)
request-problem-information (8-bit unsigned integer)
request-response-information (8-bit unsigned integer)
session-expiry-interval (32-bit unsigned integer — note: use -x instead)
topic-alias-maximum (16-bit unsigned integer)
user-property (UTF-8 string pair)

user-property (UTF-8 string pair)

✨ Unsubscribe ✨

user-property (UTF-8 string pair)

✨ Disconnect ✨

session-expiry-interval (32-bit unsigned integer)
user-property (UTF-8 string pair)

✨ Will properties ✨

content-type (UTF-8 string)
correlation-data (binary data — note: treated as a string)
message-expiry-interval (32-bit unsigned integer)
payload-format-indicator (8-bit unsigned integer)
response-topic (UTF-8 string)
user-property (UTF-8 string pair)
will-delay-interval (32-bit unsigned integer)

🚪 EXIT STATUS 🚪

So like, it's Zero on success, or non-zero on error — pretty standard main character behaviour. ✨ But here's the tea: if the broker refuses the connection at the MQTT level, your exit code is the CONNACK reason code. And if some other error happens, the exit code is a libmosquitto return value. iykyk.

MQTT v3.1.1 CONNACK codes:

0 Success 🎉
1 Connection refused: Bad protocol version
2 Connection refused: Identifier rejected
3 Connection refused: Server unavailable
4 Connection refused: Bad username/password
5 Connection refused: Not authorized

MQTT v5 CONNACK codes:

0 Success 🎉
128 Unspecified error
129 Malformed packet
130 Protocol error
131 Implementation specific error
132 Unsupported protocol version
133 Client ID not valid
134 Bad username or password
135 Not authorized
136 Server unavailable
137 Server busy
138 Banned 💀
139 Server shutting down
140 Bad authentication method
141 Keep alive timeout
142 Session taken over
143 Topic filter invalid
144 Topic name invalid
147 Receive maximum exceeded
148 Topic alias invalid
149 Packet too large
148 Message rate too high
151 Quota exceeded
152 Administrative action
153 Payload format invalid
154 Retain not supported
155 QoS not supported
156 Use another server
157 Server moved
158 Shared subscriptions not supported
159 Connection rate exceeded
160 Maximum connect time
161 Subscription IDs not supported
162 Wildcard subscriptions not supported

Other codes:

27 Timed out waiting for message 😭

🍓 EXAMPLES 🍓

Real talk: these really are examples — the subscriptions will totally work if you run them as shown, but like… something has to actually be publishing messages on those topics for you to receive anything, bestie. No publisher, no vibes. 🙈

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 one 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/#

Specify the output format as "ISO-8601 date : topic : payload in hex"

mosquitto_sub -F '@Y-@m-@dT@H:@M:@S@z : %t : %x' -t '#'

Specify the output format as "seconds since epoch.nanoseconds : retained flag : qos : mid : payload length"

mosquitto_sub -F '%@s.@N : %r : %q : %m : %l' -q 2 -t '#'

Topic and payload output, but with colour where supported. Obsessed, honestly 🌈

mosquitto_sub -F '\e[92m%t \e[96m%p\e[0m' -q 2 -t '#'

🎀 FILES 🎀

$XDG_CONFIG_HOME/mosquitto_sub, $HOME/.config/mosquitto_sub, $HOME/snap/mosquitto/current/.config/mosquitto_sub (for snap installs) — configuration file for default options.

💀 BUGS 💀

Mosquitto bug information can be found at https://github.com/eclipse-mosquitto/mosquitto/issues — go snitch (lovingly) 🫶

👑 AUTHOR 👑

Roger Light <roger@atchoo.org>

And that's the whole page, bestie — you ate that 💅✨ This iconic little manual is brought to you by the Mosquitto Project, version-dated 02/09/2026, and filed under MOSQUITTO_SUB(1) in the great big man-page library in the sky. Go forth and subscribe 🎀🦋

📦 where this page comes from

alpine 3.24: mosquitto-doc 2.1.2-r1 · EPL-1.0 OR EPL-2.0
fedora 44: mosquitto 2.1.2-1.fc44 · EPL-2.0
fedora 44: mosquitto 2.1.2-1.fc44 · EPL-2.0
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash-1017 on 2026-11-04: a language model's rewrite of the original, under its terms