the first line of http request message is called ____
A request line A status line the status line status line
title: Hypertext Transfer Protocol text: transactions. An HTTP client initiates a request by establishing a Transmission Control Protocol (TCP) connection to a particular port on a server (typically port 80, occasionally port 8080; see List of TCP and UDP port numbers). An HTTP server listening on that port waits for a client's request message. Upon receiving the request, the server sends back a status line, such as "HTTP/1.1 200 OK", and a message of its own. The body of this message is typically the requested resource, although an error message or other information may also be returned. HTTP provides multiple authentication schemes such as basic title: Hypertext Transfer Protocol text: by a line feed character). The empty line must consist of only <CR><LF> and no other whitespace. In the HTTP/1.1 protocol, all header fields except "Host" are optional. A request line containing only the path name is accepted by servers to maintain compatibility with HTTP clients before the HTTP/1.0 specification in . The response message consists of the following: The status line and other header fields must all end with <CR><LF>. The empty line must consist of only <CR><LF> and no other whitespace. This strict requirement for <CR><LF> is relaxed somewhat within message bodies for consistent use of other system title: Hypertext Transfer Protocol text: IIS supports a proprietary "TRACK" method, which behaves similarly, and which is likewise recommended to be disabled. In HTTP/1.0 and since, the first line of the HTTP response is called the "status line" and includes a numeric "status code" (such as "404") and a textual "reason phrase" (such as "Not Found"). The way the user agent handles the response depends primarily on the code, and secondarily on the other response header fields. Custom status codes can be used, for if the user agent encounters a code it does not recognize, it can use the first digit of the code to title: Hypertext Transfer Protocol text: linebreaks such as <CR> or <LF> alone. Below is a sample conversation between an HTTP client and an HTTP server running on www.example.com, port 80. As mentioned in the previous sections, all the data is sent in a plain-text (ASCII) encoding, using a two-byte CR LF ('\r\n') line ending at the end of each line. A client request (consisting in this case of the request line and only one header field) is followed by a blank line, so that the request ends with a double newline, each in the form of a carriage return followed by a line feed. The title: HTTP message body text: HTTP message body HTTP Message Body is the data bytes transmitted in an HTTP transaction message immediately following the headers if there are any (in the case of HTTP/0.9 no headers are transmitted). The request/response message consists of the following: The request/status line and headers must all end with <CR><LF> (that is, a carriage return followed by a line feed). The empty line must consist of only <CR><LF> and no other whitespace. The "optional HTTP message body data" is what this article defines. This could be a response from the web server: The message body (or content) in this example