contentType

This header parameter is used to indicate the content type of the data in the "payload" or "ciphertext" field. Integers are from the "CoAP Content-Formats" IANA registry table. Text values follow the syntax of "/", where and are defined in Section 4.2 of RFC6838. Leading and trailing whitespace is not permitted. Textual content type values, along with parameters and subparameters, can be located using the IANA "Media Types" registry. Applications SHOULD provide this header parameter if the content structure is potentially ambiguous.