mosquitto_pub - an MQTT version 5/3.1.1/3.1 client for publishing simple messages



mosquitto_pub − an MQTT version 5/3.1.1/3.1 client for publishing simple messages


mosquitto_pub {[−h hostname] [−−unix socket path] [−p port−number] [−u username] [−P password−t message−topic... | −L URL} [−A bind−address] [−c] [−d] [−D command identifier value] [−i client−id] [−I client−id−prefix] [−k keepalive−time] [−−nodelay] [−q message−QoS] [−−quiet] [−r] [−−repeat count] [−−repeat−delay seconds] [−S] [−V protocol−version] [−x session−expiry−interval] {−f file | −l | −m message | −n | −s} [−−will−topic topic [−−will−payload payload] [−−will−qos qos] [−−will−retain]] [[{−−cafile file −−capath dir} [−−cert file] [−−key file] [−−ciphers ciphers] [−−tls−version version] [−−tls−alpn protocol] [−−tls−engine engine] [−−keyform {pem engine}] [−−tls−engine−kpass−sha1 kpass−sha1] [−−tls−use−os−certs] [−−insecure]] | [−−psk hex−key −−psk−identity identity [−−ciphers ciphers] [−−tls−version version]]] [−−proxy socks−url]

mosquitto_pub [−−help]


mosquitto_pub is a simple MQTT version 5/3.1.1 client that will publish a single message on a topic and exit.


mosquitto_pub supports TLS encrypted connections. It is strongly recommended that you use an encrypted connection for anything more than the most basic setup.

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.


The options below may be given on the command line, but may also be placed in a config file located at $XDG_CONFIG_HOME/mosquitto_pub or $HOME/.config/mosquitto_pub with one pair of −option value 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 the message type options, of which only one can be specified. Note also that currently some options cannot be negated, e.g. −S. Config file lines that have a # as the first character are treated as comments and not processed any further.


Bind the outgoing connection to a local ip address/hostname. Use this argument if you need to restrict network communication to a particular interface.

−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


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

See also −−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


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

See also −−key.


An openssl compatible list of TLS ciphers to support in the client. See ciphers(1) for more information.

−d, −−debug

Enable debug messages.

−D, −−property

Use an MQTT v5 property with this publish. 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, PUBREL, 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.

−f, −−file

Send the contents of a file as the message.


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.

This option 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.


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.

−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.


Define the path to a file containing a PEM encoded private key for this client, if required by the server.

See also −−cert.


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 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

If the scheme is mqtt:// then the port defaults to 1883. If the scheme is mqtts:// then the port defaults to 8883.

−l, −−stdin−line

Send messages read from stdin, splitting separate lines into separate messages.

−m, −−message

Send a single message from the command line.

−n, −−null−message

Send a null (zero length) message.


Disable Nagle's algorithm for the socket. This means that 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.

−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.

−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.


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.

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


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.


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 to use for the message, from 0, 1 and 2. Defaults to 0.


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).

−r, −−retain

If retain is given, the message will be retained as a "last known good" value on the broker. See mqtt(7) for more information. Note that zero length payloads are never retained. If you send a zero length payload retained message it will clear any retained message on the topic.


If the publish mode is−m, −f, or −s (i.e. the modes where only a single message is sent), then −−repeat can be used to specify that the message will be published multiple times.

See also −−repeat−delay.


If using −−repeat, then the default behaviour is to publish repeated messages as soon as the previous message is delivered. Use −−repeat−delay to specify the number of seconds to wait after the previous message was delivered before publishing the next. Does not need to be an integer number of seconds.

Note that there is no guarantee as to the actual interval between messages, this option simply defines the minimum time from delivery of one message to the start of the publish of the next.

−s, −−stdin−file

Send a message read from stdin, sending the entire content as a single message.


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 on which to publish the message. See mqtt(7) for more information on MQTT topics.


Provide a protocol to use when connecting to a broker that has multiple protocols available on a single port, e.g. MQTT and WebSockets.


A valid openssl engine id. These can be listed with openssl engine command.

See also −−keyform.


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.


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.


Choose which TLS protocol version to use when communicating with the broker. Valid options are tlsv1.3, tlsv1.2 and tlsv1.1. 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.


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.

−V, −−protocol−version

Specify which version of the MQTT protocol should be used when connecting to the rmeote broker. Can be 5, 311, 31, or the more verbose mqttv5, mqttv311, or mqttv31. Defaults to 311.


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.


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


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. Note that zero length payloads are never retained. If you send a zero length payload retained message it will clear any retained message on the topic.


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


Set the session−expiry−interval property on the CONNECT packet. Applies to MQTT v5 clients only. Set to 0−4294967294 to specify the session will expire in that many seconds after the client disconnects, or use −1, 4294967295, or â 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.


mosquitto_sub 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.


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


authentication−data (binary data − note treated as a string in mosquitto_pub)

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)


content−type (UTF−8 string)

correlation−data (binary data − note treated as a string in mosquitto_pub)

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)


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 in mosquitto_pub)

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)


mosquitto_sub returns zero on success, or non−zero on error. If the connection is refused by the broker at the MQTT level, then the exit code is the CONNACK reason code. If another error occurs, the exit code is a libmosquitto return value.

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


Publish temperature information to localhost with QoS 1:

• mosquitto_pub −t sensors/temperature −m 32 −q 1

Publish timestamp and temperature information to a remote host on a non−standard port and QoS 0:

• mosquitto_pub −h −p 1885 −t sensors/temperature −m "1266193804 32"

Publish light switch status. Message is set to retained because there may be a long period of time between light switch events:

• mosquitto_pub −r −t switches/kitchen_lights/status −m "on"

Send the contents of a file in two ways:

• mosquitto_pub −t my/topic −f ./data

• mosquitto_pub −t my/topic −s < ./data

Send parsed electricity usage data from a Current Cost meter, reading from stdin with one line/reading as one message:

• | mosquitto_pub −t sensors/cc128 −l


$XDG_CONFIG_HOME/mosquitto_pub, $HOME/.config/mosquitto_pub

Configuration file for default options.


mosquitto bug information can be found at


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


Roger Light <[email protected]>

Updated 2024-01-29 - |