List and explain various fields of HTTP messages

HTTP message: HTTP messages consist of the following fields:

Message types: A HTTP message can be either a client request or a server response. The following string indicates the HTTP message type:
HTTP-message = Request | Response

Message header: The HTTP message header field can be one of the following:
General header
Request header
Response header
Entity header

Message body: Message body can be referred to as entity body if there is no transfer coding has been applied. Message body simply carries the entity body of the relevant request or response.

 Message length Message length indicates the length of the message body if it is included.

General header field: General header fields can apply both request and response messages. Currently defined general header field options are as follows:

Cache-Control

Connection

Date

Pragma

Transfer-Encoding

Upgrade

Via
Request: A request message from a client to a server includes the method to be applied to the resource, the identifier of the source, and the protocol version in use. A request message field is as follows: Request = Request-Line *( general-header | request-header | entity-header ) CRLF [ message-body ] Response: An HTTP server returns a response after evaluating the client request. A response message field is as follows:
Request = Request-Line *( general-header | request-header | entity-header ) CRLF [ message-body ] Entity: Either the client or server might send Entity in the request message or the response message, unless otherwise indicated. Entity consists of the following:
Entity header fields
Entity body