20.15 Content-Type The Content-Type header field indicates the media type of the message-body sent to the recipient. The "media-type" element is defined in [H3.7]. The Content-Type header field MUST be present if the body is not empty. If the body is empty, and a Content-Type header field is present, it indicates that the body of the specific type has zero length (for example, an empty audio file). “Content-Type”报头字段指示发送给收件人的消息体的媒体类型。【H3.7】中定义了“media-type”元素。如果正文不为空,则必须存在“Content-Type”报头字段。如果消息体为空,并且存在“Content-Type”报头字段,则表示特定类型的消息体长度为零(例如,空音频文件)。 The compact form of the header field is c. 报头字段的紧凑形式是c。 Examples: 示例: Content-Type: application/sdp c: text/html; charset=ISO-8859-4