2020-04-14 05:19:12 -04:00
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# MQTT in curl
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## Experimental!
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MQTT support in curl is considered **EXPERIMENTAL** until further notice. It
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needs to be enabled at build-time. See below.
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After the initial merge, further development and tweaking of the MQTT support
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in curl will happen in the master branch using pull-requests, just like
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ordinary changes.
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Experimental support for MQTT means that we **do not guarantee** that the
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current protocol functionality will remain or remain this way going forward.
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There are no API or ABI promises for experimental features as for regular curl
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features.
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Do not ship anything with this enabled.
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## Build
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./configure --enable-mqtt
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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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Example subscribe:
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curl mqtt://host/home/bedroom/temp
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Example publish:
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2020-04-14 13:07:08 -04:00
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curl -d 75 mqtt://host/home/bedroom/dimmer
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2020-04-14 05:19:12 -04:00
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## What does curl deliver as a response to a subscribe
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It 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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- No username support
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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 username/password support
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- No TLS (mqtts) support
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- Naive EAGAIN handling won't handle split messages
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## Work
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1. Write a mqtt server for the test suite
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2. Create a few tests verifying the existing mqtt functionality
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3. Work on fixing some of the worst limitations - with accompanying tests
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4. Consider replacing the client-side MQTT code with wolfMQTT
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## Credits
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The initial MQTT patch was authored by Björn Stenberg. This work is built upon
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that patch and has been expanded since.
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