Coap.getResponseContentFormat()
DESCRIPTION
Get response content format.
DECLARATION
int getResponseContentFormat()
THROWS EXCEPTIONS
NabtoRuntimeException:- with error code 
NO_DATAif the response does not include a content format. NabtoRuntimeException:- with error code 
INVALID_STATEif the response is not available. 
RETURNS
the response content format or -1 if no content format is set in the response.