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--- iot:aws:json [2020/06/11 13:04] – created atolstov
+++ iot:aws:json [2020/06/12 10:05] (current) – ↷ Links adapted because of a move operation atolstov
@@ Line 1: / Line 1: @@
-json
+==== JSON formatted payload ====
+It is widely used MQTT payload format JSON.
+Let’s write a small script which will use inbuild library to encode any WebHMI register values to JSON formatted strings.
+Here is the code example to encode a string type message with Amazon Web Services (AWS) [[https://docs.aws.amazon.com/iot/latest/developerguide/device-shadow-document-syntax.html|Thing Report Shadow]] JSON format.
+<code lua - AWS_thing_report.lua>
+function main (userId)
+    local decoded =
+    {
+    state =
+        {
+        reported =
+            {
+            timestamp       =   os.date("%Y-%m-%dT%H:%M:%S", os.time() - 3 * 60 * 60),
+            message         =   "Hello, WebHMI!"
+            }
+        }
+    }
+    encoded = cjson.encode( decoded )
+                                        DEBUG(encoded)
+    WriteReg("mqtt_publish", encoded); -- Test Publish (iot-test@MQTT WebHMI Client)
+end
+</code>
+To check the result of script work let’s check “iot-test” subscribed topic in MQTT.fx.
+{{ iot:mqtt:client:json:протокол_связи_mqtt_на_webhmi_json_encode_test.png?direct |}}
+//Hint: There is drop-down list with MQTT payload format selector in the lower right corner.//