The response content format.
When the class is operating in client mode (i.e., the Listening property is disabled), this property is populated with the content format included in incoming responses anytime the RequestComplete event fires.
When the class is operating in server mode (i.e., the Listening property is enabled), this property specifies the content format that should be included in outgoing responses (regardless of whether they are sent immediately after Request fires, or later using SendResponse or SendNotification).
In either case, the valid set of values for this property is -1, or a value in the range 0 to 65535. -1 prevents a Content-Format option from being included when sending a response, or indicates that one was not included in a received response.
The following table provides a (non-exhaustive) list of some of the more common content formats; refer to the IANA's CoAP Content-Formats registry for a full list.
|-1 (default)||Content-Format option not included.|
This property is not available at design time.