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GadgetKeeper and Thing exchange messages using an use external MQTT broker :to exchange messages. 

Connection Settings

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Field	Required	Description	Dialog
Name	x	Connection connection name	Image Modified
Protocol	x	Select select "json-rpc over mqtt"
Host	x	MQTT broker host
Port	x	MQTT broker port
Secure		When checked, the connection uses use MQTTS
Request topic	x	Topic topic to send a command
Response topic	x	Topic topic to receive a response
Connection, ms	x	Number number of milliseconds GadgetKeeper can spend spent on connection to MQTT broker
Response, ms	x	Number number of milliseconds GadgetKeeper will wait for Thing to receive message and send response
Date format	x	Date date format representation: iso-8601 - date is represented as string (example: "2013-05-27UTC06:07:16Z") unix-timestamp - not supported, date is represented as number (example: 1369634836)
Description		Connection connection description

Example

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Scenario Using MQTT

Device (thing) responds to a request from GadgetKeeper:

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Given

1. Thing has remote method "echo"
2. Thing will want to be set up able to execute handle this method in response to a command from GadgetKeeper

Workflow

1. Thing establishes MQTT connection to the specified MQTT Broker server
2. Thing subscribes to the specified request topic
3. GadgetKeeper subscribes to the specified response topic

4. GadgetKeeper sends (publishes) a JSON-RPC request message to the request topic: 

   Code Block
   language javascript
   { "jsonrpc":"2.0", "method":"echo", "params":"hello world!", "id":990909000 }

5. Thing receives the JSON request message and sends (publishes) send a response back to the response topic:

   Code Block
   { "jsonrpc":"2.0", "result":"hello world!", "id":990909000 }

6. GadgetKeeper receives the response and disconnects from MQTT broker

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Workflow

...

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{
        "jsonrpc":"2.0",
        "id":"7755",
        "method":"things.methods.execute",
        "params": {
                "thingId":"990fc000c90211e2b5566c626dd90e00",
                "methodId":"99614181155811e4abd06c626dd90e00",
                "async":true,
                "args":"hello world!"
        }
}

...

GadgetKeeper receives the JSON request message and sends (publishes) a response back to the response topic:

{
        "jsonrpc":"2.0",
        "id":"7755",
        "result":"hello world!"
}

...

Thing receives the response and disconnects from MQTT broker