MOSQUITTO_RR(1)

📦
version 2.1.2 · 13 versions
, in alpine 3.24, fedora 44

🌸 NAME 🌸

Okay bestie, welcome to mosquitto_rr(1) — the manual page for the MQTT version 5/3.1.1 client that does request/response messaging. 💖

✨ SYNOPSIS ✨

mosquitto_rr [options] -e response-topic -t message-topic...
             {payload-options}

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:
              [--latency] [-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-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] [-N] [--pretty] [--quiet] [-R] [-v]

payload-options:
                 -f file | -m message | -n | -s

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_rr [--help]

🦋 DESCRIPTION 🦋

So mosquitto_rr is an MQTT version 5/3.1.1 client, and its whole main-character thing is publishing a request message and then waiting for a response. When you’re using MQTT v5 — which is the default — mosquitto_rr will use the Request-Response feature. 💅

The important options are -t, -e, and one of -f, -m, -n, and -s. Those are the ones you actually need to clock, fr fr.

Example:

mosquitto_rr -t request-topic -e response-topic -m message

🔐 ENCRYPTED CONNECTIONS 🔐

This client supports TLS encrypted connections. It is strongly recommended that you use an encrypted connection for anything more than the most basic setup. No cap, please don’t be out here raw-dogging your MQTT traffic for no reason. 😭

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.

To enable TLS connections when using TLS-PSK, you must use the --psk and the --psk-identity options.

👑 OPTIONS 👑

There are three ways to provide options to mosquitto_rr: the default config file, a specified config file, or options on the command line.

🎀 Default Config File 🎀

The default config file is located at $XDG_CONFIG_HOME/mosquitto_rr or $HOME/.config/mosquitto_rr on POSIX systems, or %USERPROFILE%\mosquitto_rr on Windows. Slay, now you know where to put your little settings. ✨

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. 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.

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. Very demure, very mindful. 🎀

💜 Config File 💜

Available from version 2.1.

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.

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. Basically: tell it which local lane to use. 🛣️
  • -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.

If using this option, the client id must be set manually with --id.

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

See also --capath.

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

For --capath to work correctly, the certificate files must have ".crt" as the file ending and you must run "openssl rehash <path to capath>" each time you add/remove a certificate.

See also --cafile.

  • --cert — Define the path to a file containing a PEM encoded certificate for this client, if required by the server.

See also --key and the Encrypted Connections section.

  • --ciphers — An openssl compatible list of TLS ciphers to support in the client. See ciphers(1) for more information.
  • -d, --debug — Enable debug messages. Your fave little “what is happening” switch. 🔍
  • -D, --property — Set MQTT v5 properties for with this client. If you use this option, the client will be set to be an MQTT v5 client. This option has two forms:
-D command identifier value
-D command identifier name value

command is the MQTT command/packet identifier and can be one of CONNECT, PUBLISH, PUBACK, PUBREC, PUBCOMP, SUBSCRIBE, UNSUBSCRIBE, DISCONNECT, AUTH, or WILL. The properties available for each command are listed in the Properties section.

identifier is the name of the property to add. This is as described in the specification, but with - as a word separator. For example: payload-format-indicator. More details are in the Properties section.

value is the value of the property to add, with a data type that is property specific.

name is only used for the user-property property as the first of the two strings in the string pair. In that case, value is the second of the strings in the pair.

  • -e — Response topic. The client will subscribe to this topic to wait for a response. This is lowkey the “where’s my reply going” option. 💌
  • -f, --file — Send the contents of a file as the message.
  • -F — Specify output printing format. This option allows you to choose what information from each message is printed to the screen. See the Output Format section below for full details.

This option overrides the -v option, but does not override the -N option.

  • --help — Display usage information.
  • -h, --host — Specify the host to connect to. Defaults to localhost.
  • -i, --id — The id to use for this client. If not given, a client id will be generated depending on the MQTT version being used. For v3.1.1/v3.1, the client generates a client id in the format mosq-XXXXXXXXXXXXXXXXXX, where the X are replaced with random alphanumeric characters. For v5.0, the client sends a zero length client id, and the server will generate a client id for the client. ✨
  • -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.
  • --insecure — 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 only. 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. Like, bestie, do not ship this. 💀
  • -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.
  • --key — Define the path to a file containing a PEM encoded private key for this client, carrying out mutual TLS with the server.

See also --cert and the Encrypted Connections section.

  • --keyform — Specifies the type of private key in use when making TLS connections.. This can be "pem" or "engine". This parameter is useful when a TPM module is being used and the private key has been created with it. Defaults to "pem", which means normal private key files are used.

See also --tls-engine.

  • -L, --url — 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.

  • --latency — Available from version 2.1.

If this option is specified, mosquitto_rr will print out the latency between it starting to publish a request and the response arriving. This number includes both the broker and client processing times, as well as any inherent network latency.

This can be used to measure message delivery latency very simply by specifying an identical request and response topic.

The --nodelay option will be automatically used when --latency is in use. ⏱️

  • -m, --message — Send a single request message from the command line.
  • -N — okay so this one says do not append an end of line character to the payload when printing, bestie. That lets you stream payload data from multiple messages directly to another application unmodified. It only really makes sense when you're not using -v, no cap. 💅
  • -n, --null-message — send a null (zero length) message. Short, sweet, iconic. ✨
  • --nodelay — disable Nagle's algorithm for the socket. This means the latency of sent messages is reduced, which is particularly noticeable for small, reasonably infrequent messages. Using this option may result in more packets being sent than would normally be necessary. Lowkey a tradeoff, but you knew that. 🦋
  • --no-tls — available from version 2.1. Disable all use of TLS encryption. This is useful if you specify TLS options in a configuration file but want to disable those options. It also stops the automatic use of TLS when connecting to port 8883. Bye-bye automatic TLS, periodt. 🎀
  • -o config-file — available from version 2.1. Load options from a config file. See the Default Config File and Config File sections at the start of the Options section. Config file girlies rise. 📁
  • -p, --port — connect to the port specified. If not given, the default of 1883 for plain MQTT or 8883 for MQTT over TLS will be used. Port check: iconic. 🔌
  • -P, --pw — provide a password to be used for 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. Do not skip the username, bestie, unless you want chaos. 🔐
  • --pretty — when using the JSON output format %j or %J, the default is to print in an unformatted fashion. Specifying --pretty prints messages in a prettier, more human readable format. It's giving glow-up for JSON. 💖
  • --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). Proxy lore, iykyk. 🧚
  • --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. Pre-shared-key realness. 🔑
  • --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. Identity is the moment. 🪪
  • -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 applies to all topics subscribed to in a single instance of this client. One client, one QoS vibe. 📶
  • --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). Quiet mode still has receipts for bad input, bestie. 🤫
  • -R — 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. See also --retain-handling. Stale messages? Not on my watch. 🫶
  • --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. Always, always, always. ⭐
    • 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. New subscription energy only. 🌸
    • never — never deliver retained messages. Never ever, fr fr. 💀
  • -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>. DNS detective era. 🕵️‍♀️
  • -s, --stdin-file — send a request message read from stdin, sending the entire content as a single message. Stdin to broker pipeline, slay. 📥
  • -t, --topic — the MQTT topic where the request message will be sent. Topic? Chosen. Main character topic. 🎯
  • --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. One port, multiple protocols, very demure. 🌈
  • --tls-engine — a valid openssl engine id. These can be listed with the openssl engine command. See also --keyform. Engine check, bestie. ⚙️
  • --tls-engine-kpass-sha1 — SHA1 of the private key password when using an 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. Password hash to the engine, no prompt, no drama. 🔑
  • --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. This option should be used for debugging only, it must not be used in production. Not me reminding you: debugging only, no cap. 🚨
  • --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. OS certs coming in clutch. 🍓
  • --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. Match the broker, bestie. It's giving compatibility. 🔒
  • -u, --username — provide a username to be used for authenticating with the broker. See also the --pw argument. Username and password, the classic duo. 👑
  • --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. Unix socket supremacy, lowkey. 🧦
  • -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. Verbose mode ate, honestly. 🗣️
  • -V, --protocol-version — specify which version of the MQTT protocol should be used when connecting to the remote broker. Can be 5, 311, 31, or the more verbose mqttv5, mqttv311, or mqttv31. Defaults to 311. Pick your protocol era. 📱
  • -W — provide a timeout as an integer number of seconds. The client will stop processing messages and disconnect after this number of seconds has passed. The timeout starts just after the client has connected to the broker. Countdown starts after connect, bestie. ⏱️
  • --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 conjunction with --will-topic. Your goodbye message, stored and ready. 💌
  • --will-qos — the QoS to use for the Will. Defaults to 0. This must be used in conjunction with --will-topic. Will QoS, set it right. 📬
  • --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. Retained Will? Iconic exit strategy. 🫶
  • --will-topic — the topic on which to send a Will, in the event that the client disconnects unexpectedly. The topic of your dramatic exit. 🎭
  • --ws — connect using WebSockets instead of plain TCP. WebSocket vibes only. 🌐
  • -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 not given. If the session is set to never expire, either with -x or -c, then a client id must be provided. Session expiry lore: do not forget the client id, bestie. ♾️

💬 OUTPUT FORMAT 💬

okay so there are literally three ways to format the printed output, bestie. In all of them, a new-line character gets appended for each message received — unless you pass the -N argument. ✨

Payload-only is the default output format, and it prints the payload exactly as it's received. No notes, no commentary, just the raw vibes.

Verbose mode is what you get with -v — it prints the message topic and the payload, separated by a space. Simple, iconic.

The final option is formatted output, which lets you define a custom output format, and it's fully controlled with the -F format-string option. The format string is a free text string where interpreted sequences get 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 so you don't have to type out long date format strings, for example.
  • Sequences starting with @ get passed to the strftime(3) function (with the @ replaced with a % — note that only the character immediately after the @ is passed to strftime). This lets you construct a wide variety of time-based outputs. The output options for strftime vary from platform to platform, so pls check what's available on yours.
  • One extension to strftime is provided, and it's @N, which you can use to grab 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. no cap. 💅

🔢 Hexadecimal binary field width

The %x and %X parameters output the payload as a single hexadecimal string by default. It's 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:

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

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

🧮 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. Do not 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're unsure what floating representation your platform is using, then it's 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 an 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's 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 💜

The -D / --property option allows adding properties to different stages of the mosquitto_rr run. The properties supported for each command are as follows:

🔌 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)

📤 Publish

  • 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)
  • topic-alias (16-bit unsigned integer)
  • user-property (UTF-8 string pair)

📥 Subscribe

  • 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

okay so this is the part where you find out how it went 💅 zero means slay, we ate, everything worked. anything that's not zero means nope, something went sideways.

here's the tea though: if the broker itself refuses you at the MQTT level (like, it heard you and said "no <3"), then the exit code is the CONNACK reason code. so you can literally read the break-up message straight off $?. and if it's some other kind of error, then the exit code is a libmosquitto return value. iykyk 🦋

🌸 MQTT v3.1.1 CONNACK codes

  • 0 — Success ✨ (the good one, bestie)
  • 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

this list is lowkey long, but every single one matters, so we're doing all of them, no skipping 🙈

  • 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
👀 and yes, 148 really does show up twice in this list — that's exactly what the page says, so i'm giving it to you character for character. not my business, i just work here 🎀

🫶 Other codes

  • 27 — Timed out waiting for message

📁 FILES

  • $XDG_CONFIG_HOME/mosquitto_rr, $HOME/.config/mosquitto_rr, $HOME/snap/mosquitto/current/.config/mosquitto_rr (for snap installs) — the configuration file where your default options live. this is the "set it and forget it" energy 👑

💀 BUGS

need to snoop on mosquitto bugs? they live right here, bestie:

https://github.com/eclipse-mosquitto/mosquitto/issues

🌈 SEE ALSO

go read these next, they're all icons in their own right:

mosquitto(7), mqtt(7), mosquitto_pub(1), mosquitto_sub(1), mosquitto(8), libmosquitto(3), mosquitto-tls(7)

👑 AUTHOR

Roger Light <roger@atchoo.org> — the main character who made all of this happen, we stan fr fr 💖

and that's a wrap on MOSQUITTO_RR(1), bestie!! 🎀 this whole thing ships with the Mosquitto Project, dated 02/09/2026, and the man page tag is MOSQUITTO_RR(1) — go forth and request/response your heart out 💅✨🦋

📦 where this page comes from