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    1: # MQTT in curl
    2: 
    3: ## Experimental!
    4: 
    5: MQTT support in curl is considered **EXPERIMENTAL** until further notice. It
    6: needs to be enabled at build-time. See below.
    7: 
    8: After the initial merge, further development and tweaking of the MQTT support
    9: in curl will happen in the master branch using pull-requests, just like
   10: ordinary changes.
   11: 
   12: Experimental support for MQTT means that we **do not guarantee** that the
   13: current protocol functionality will remain or remain this way going forward.
   14: There are no API or ABI promises for experimental features as for regular curl
   15: features.
   16: 
   17: Do not ship anything with this enabled.
   18: 
   19: ## Build
   20: 
   21:     ./configure --enable-mqtt
   22: 
   23: ## Usage
   24: 
   25: A plain "GET" subscribes to the topic and prints all published messages.
   26: Doing a "POST" publishes the post data to the topic and exits.
   27: 
   28: Example subscribe:
   29: 
   30:     curl mqtt://host/home/bedroom/temp
   31: 
   32: Example publish:
   33: 
   34:     curl -d 75 mqtt://host/home/bedroom/dimmer
   35: 
   36: ## What does curl deliver as a response to a subscribe
   37: 
   38: It outputs two bytes topic length (MSB | LSB), the topic followed by the
   39: payload.
   40: 
   41: ## Caveats
   42: 
   43: Remaining limitations:
   44:  - No username support
   45:  - Only QoS level 0 is implemented for publish
   46:  - No way to set retain flag for publish
   47:  - No username/password support
   48:  - No TLS (mqtts) support
   49:  - Naive EAGAIN handling won't handle split messages
   50: 
   51: ## Work
   52: 
   53: 1. Write a mqtt server for the test suite
   54: 2. Create a few tests verifying the existing mqtt functionality
   55: 3. Work on fixing some of the worst limitations - with accompanying tests
   56: 4. Consider replacing the client-side MQTT code with wolfMQTT
   57: 
   58: ## Credits
   59: 
   60: The initial MQTT patch was authored by Björn Stenberg. This work is built upon
   61: that patch and has been expanded since.