Wong - HTTP Pocket Reference

1. The first line of this request(GET / HTTP/1.1) requests a document at / from theserver. HTTP/1.1 is given as the version of theHTTP protocol that the browser uses.

2. The second line tells the server what kind of documents are acceptedby the browser.

3. The third line indicates that the preferred language is English. Thisheader allows the client to specify a preference for one or morelanguages, in the event that a server has the same document inmultiple languages.

4. The fourth line indicates that the client understands how tointerpret a server response that is compressed with the gzip ordeflate algorithm.

5. In the fifth line, beginning with the stringUser-Agent, the client identifies itself asMozilla version 4.0, running on Windows NT. In parenthesis itmentions that it is really Microsoft Internet Explorer version 5.01.

6. The sixth line tells the server what the client thinks theserver's hostname is.This header is mandatory in HTTP 1.1, but optional in HTTP 1.0. Sincethe server may have multiple hostnames, the client indicates whichhostname is being requested. In this environment, a web server canhave a different document tree for each hostname assigned to it. Ifthe client hasn't specified the server's hostname, theserver may be unable to determine which document tree to use.

7. The seventh line (Connection:) tells theserver to keep the TCP connection open until explicitly told todisconnect. Under HTTP 1.1, the default server behavior is to keepthe connection open until the client specifies that the connectionshould be closed. The standard behavior in HTTP 1.0 is to close theconnection after the client's request. See the discussion in later in this book for details.

Given arequest like the one previously shown, the server looks for theserver resource associated with "/" and returns it to thebrowser, preceding it with header information in its response. Theresource associated with the URL depends on how the server isimplemented. It could be a static file or it could be dynamicallygenerated. In this case, the server returns:

• An image,
• Text,
• and a

If you look at this response, you'll see it begins with aseries of lines that specify information about the document and aboutthe server itself. After a blank line, it returns the document. Lines2-9 are called the response header, and the part after thefirst blank line is called the body or entity, or entity-body.Let's look at the header information: