The server interprets the request received, maps the request into a program kept in the server, executes the program, and returns the output of the program to the client.The server interprets the request received, maps the request into a file under the server's document directory, and returns the file requested to the client.When this request message reaches the server, the server can take either one of these actions:
USING PACKET SENDER TO GET ASCII HTML WINDOWS
User-Agent: Mozilla/4.0 (compatible MSIE 6.0 Windows NT 5.1) The path and file name for the resource to be located is " /docs/index.html".Īs mentioned, whenever you enter a URL in the address box of the browser, the browser translates the URL into a request message according to the specified protocol and sends the request message to the server.įor example, the browser translated the URL into the following request message: GET /docs/index.html HTTP/1.1 Path-and-file-name: The name and location of the requested resource, under the server document base directory.įor example, in the URL, the communication protocol is HTTP the hostname is The port number was not specified in the URL, and takes on the default number, which is TCP port 80 for HTTP.Port: The TCP port number that the server is listening for incoming requests from the clients.Hostname: The DNS domain name (e.g., or IP address (e.g., 192.128.1.2) of the server.Protocol: The application-level protocol used by the client and server, e.g., HTTP, FTP, and telnet.URL has the following syntax: protocol:// hostname: port/ path-and-file-name This process is illustrated below: Uniform Resource Locator (URL)Ī URL (Uniform Resource Locator) is used to uniquely identify a resource over the web. The HTTP server interprets the request message, and returns you an appropriate response message, which is either the resource you requested or an error message. , the browser turns the URL into a request message and sends it to the HTTP server. Whenever you issue a URL from your browser to get a web resource using HTTP, e.g. It is a generic, stateless, protocol which can be used for many tasks beyond its use for hypertext, such as name servers and distributed object management systems, through extension of its request methods, error codes and headers." Quoting from the RFC2616: "The Hypertext Transfer Protocol (HTTP) is an application-level protocol for distributed, collaborative, hypermedia information systems.HTTP permits negotiating of data type and representation, so as to allow systems to be built independently of the data being transferred.In other words, the current request does not know what has been done in the previous requests. In other words, HTTP is a pull protocol, the client pulls information from the server (instead of server pushes information down to the client). The server, in turn, returns a response message. An HTTP client sends a request message to an HTTP server. HTTP is an asymmetric request-response client-server protocol as illustrated.HTTP (Hypertext Transfer Protocol) is perhaps the most popular application protocol used in the Internet (or The WEB). In order for proper communication to take place between the client and the server, these applications must agree on a specific application-level protocol such as HTTP, FTP, SMTP, POP, and etc. Many applications are running concurrently over the Web, such as web browsing/surfing, e-mail, file transfer, audio & video streaming, and so on. Internet (or The Web) is a massive distributed client/server information system as depicted in the following diagram. HTTP (HyperText Transfer Protocol) Basics Introduction The WEB
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