API description

The following section describes the options provided by the JSON Data Interface with the help of short example requests and responses. The API is equally valid for access via MQTT or via ADS.

Type	Request/Response	Sample of the JSON payload
Reading a variable	Request	{"symbol":"MAIN.nCounter"}
	Response	{"symbol":"MAIN.nCounter", "value":42}
Reading a variable and its data type	Request	{"symbol":"MAIN.nCounter", "datatype":null}
	Response	{"symbol":"MAIN.nCounter", "value":42, "datatype":INT}
Simultaneous reading of several variables	Request	[{"symbol": "MAIN.nCounter"},{"symbol":"MAIN.nSecCounter"}]
	Response	[{"symbol":"MAIN.nCounter","value":42 },{"symbol":"MAIN.nSecCounter, "value":35}]
Reading the TwinCAT symbol info	Request	{"symbols":null}
	Response	Complete symbol info
Writing a variable	Request	{"symbol":"MAIN.nCounter","value":42}
	Response	{"symbol":"MAIN.nCounter","value":42}
Writing several variables	Request	[{"symbol":"MAIN.nCounterˮ, "value":42},{"symbol":"MAIN.nSecCounter", "value":35}]
	Response	[{"symbol":"MAIN.nCounter","value":42},{"symbol":"MAIN.nSecCounter","value":35}]
Method calls, optionally with input and output parameters	Request	{"symbol": "MAIN.fbTester#M_Add","parameter":{ "intA":42, "intB":35}}
	Response	{"symbol":"MAIN.fbTester#M_Add", "value":77}
	Response with additional outputs	{"symbol":"MAIN.fbTester#M_Add","value":77,"parameter":{"intC":32, "intD":64}}