NAME¶

paho_c_sub - receive (subscribe to) data from an MQTT server

SYNOPSIS¶

paho_c_sub [topic] [-t|--topic topic] [-c|--connection connection] [-h|--host hostname] [-p|--port portnumber] [-i|--clientid clientid] [-u|--username username] [-P|--password password] [-k|--keepalive keepalive-timeout] [-V|--MQTT-version 31|311|5]
[-q|--qos 0|1|2] [-R|--no-retained] [--delimiter delimiter] [--no-delimiter]
[--quiet] [--verbose] [--trace min|max|error|protocol]
[--will-topic will-topic] [--will-payload will-payload] [--will-retain] [--will-qos 0|1|2]
[--cafile cafile] [--capath capath] [--cert certfile] [--key keyfile] [--keypass password] [--ciphers cipher-string] [--insecure]

DESCRIPTION¶

paho_c_sub receives data from an MQTT server using the Eclipse Paho C client asynchronous library (MQTTAsync). MQTT is a protocol, operating over TCP/IP, which allows programs to easily communicate with each other through a server. Messages are published to topics and delivered to any subscribers to those topics. The corresponding publisher program paho_c_pub allows MQTT messages to be sent.

The default mode of operation is to output each message to stdout terminated by the delimiter.

OPTIONS¶

-t

--topic

The MQTT topic to publish the data to.

-c

--connection

The MQTT URI to connect to, a combination of transport prefix, host, port and for websockets, topic. To connect using TCP use the tcp prefix, for example: tcp://localhost:1883. An example using SSL/TLS: ssl://localhost:1883. An example for websockets, insecure: ws://localhost:1883/topic, and secure: wss://localhost:80/topic.

-h

--host

The TCP/IP host name of the MQTT server to connect to. Along with the --port option, an older alternative to using --connection.

-p

--port

The TCP/IP port number of the MQTT server to connect to. Along with the --host option, an older alternative to using --connection.

-q

--qos

The MQTT QoS on which to publish the message. The alternatives are 0, 1 or 2.

-V

--MQTTversion

The version of the MQTT protocol to use. Valid options are 31 (or mqttv31), 311 (mqttv311) and 5 (or mqttv5).

--quiet

Do not print error messages.

--trace

Print library internal trace. Valid levels are min, max, error and protocol.

-R

--no-retained

Do not print messages which have the MQTT retained flag set.

--delimiter

The delimiter string to append to each message when printing. Defaults to newline.

--no-delimiter

Do not add a delimiter to each message when printing.

--will-topic

Sets the MQTT will message topic to publish to. If the application ends without sending an MQTT disconnect, the will message will be published to this topic.

--will-payload

Only used if will-topic is set. Sets the MQTT will message to be published.

--will-qos

Only used if will-topic is set. Sets the MQTT QoS at which the will message is published. The alternatives are 0, 1 or 2.

--will-retain

Only used if will-topic is set. Sets the MQTT retained flag on the will message.

--cafile

Only used with a TLS connection. The name of a file for the OpenSSL trust store.

--capath

Only used with a TLS connection. The name of a directory holding OpenSSL trusted certificates.

--cert

Only used with a TLS connection. The name of a file for the TLS keystore containing a client certificate to be presented.

--key

Only used with a TLS connection. The name of a file containing the client private key.

--keypass

Only used with a TLS connection. The password for the client private key file, if needed.

--ciphers

Only used with a TLS connection. A list of cipher suites that the client will present to the server during the TLS handshake.

--insecure

Only used with a TLS connection. Don't check that the server certificate common name matches the hostname.