e4aa07b526
Some of the wording in the mqtt.md confused me as to how the commands were used and what they did, so I cleared up some of the wording to better explain what each command does. Closes #15451
50 lines
1.1 KiB
Markdown
50 lines
1.1 KiB
Markdown
<!--
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Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
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SPDX-License-Identifier: curl
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-->
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# MQTT in curl
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## Usage
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A plain "GET" subscribes to the topic and prints all published messages.
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Doing a "POST" publishes the post data to the topic and exits.
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### Subscribing
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Command usage:
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curl mqtt://host/topic
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Example subscribe:
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curl mqtt://host.home/bedroom/temp
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This will send an MQTT SUBSCRIBE packet for the topic `bedroom/temp` and listen in for incoming PUBLISH packets.
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### Publishing
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Command usage:
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curl -d payload mqtt://host/topic
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Example publish:
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curl -d 75 mqtt://host.home/bedroom/dimmer
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This will send an MQTT PUBLISH packet to the topic `bedroom/dimmer` with the payload `75`.
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## What does curl deliver as a response to a subscribe
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Whenever a PUBLISH packet is received, curl outputs two bytes topic length (MSB | LSB), the topic followed by the
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payload.
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## Caveats
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Remaining limitations:
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- Only QoS level 0 is implemented for publish
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- No way to set retain flag for publish
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- No TLS (mqtts) support
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- Naive EAGAIN handling does not handle split messages
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