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Device Protocol » History » Version 4

Hammel, 10 Mar 2016 16:07

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h1. Device Protocol
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The device protocol defines the messaging that occurs between an IoT device and the PiBox server.  
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h2. Registration
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Registration is initiated by the IoT device.  It sends a multicast packet to the PiBox server.  The packet does not need to contain any information.  It's purpose is to advertise the IP address of the IoT device.  
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The server captures the message and then queries the device for type, features and configuration which is stored in the piboxd daemon and to file as needed.
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h2. Queries
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A query is made from the server to the IoT device using a web URL.  The URL is of the format
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<pre>
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  http://<ipaddress>/im/<version>/<command>
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</pre>
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POST variables are used for arguments to the command.
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Some commands are common to all devices.
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<pre>
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  get: arguments include config, registration
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  set: arguments include config
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</pre>
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Other commands are specific to the device and can be identified in the config response.
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h2. Query Response
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A query response is provided as JSON text in the body of the page returned to the caller.  For a registration request the device returns it's identity and feature list.  For a config request the device returns its current settings associated with the features it supports.
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h3. Identify
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The identity is the device name.  This is free format and is used to identify the device to the server.
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h3. Features
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A device can specify a collection of features.  The collection is a set of names and associated data types and values. The data type for the feature and is one of num, text, range, or set.  If a feature is of type of range then the range is specified as name-range.  If the type is set then the set is specified as name-set. A field can have a name and a display name, which is represented as name-display.
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<pre>
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{
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    "identity": "abcd", 
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    "features": {
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        "damper":             "set", 
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        "damper-display":     "Vent Damper", 
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        "damper-set":         "0,25,50,75,100", 
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    }
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}
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</pre>
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Features are the way a device specifies how it can be configured and what data it provides.  The server can use this to dynamically build a UI for the device.
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h3. Config
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The config response contains the current settings for the named features.  
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h2. Control
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Control of a device is through a config object.  The configuration is changed by a UI application and forwarded to the IoT device.  The device attempts to apply the configuration changes, which may or may not succeed.  Success is not specified on a configuration change.  The only way to know if the change was applied is to query the current configuration and compare it to the change request.