orm with a MIME-like format as used in SMTP. However, HTTP messages are delivered quickly compared to SMTP messages that are stored and then forwarded. HTTP is similar to FTP in that it transfers files and uses TCP services. However HTTP uses a single TCP connection, which is not the case in FTP. In HTTP, data is transferred between client and server and there is no separate control connection. It is a stateless protocol although it uses the TCP services. The HTTP request and response messages follow the same format. The client sends a request message to the server thereby initiating the transaction. The server sends the response message back to the client (see Figure 28.1). The HTTP request message has a request line (see Figure 28.2). The request line has the request type, uniform resource locator (URL), and HTTP version. The Web Communication Request message Client Server Response message Figure 28.1 HTTP request-response model. Request message Space Request line Space Request Method:// Host: Port/Path version (method) Headers Blank line Body (optional) Figure 28.2 HTTP request message. request type categorizes the request into various methods, the URL is a standard for specifying any information on the Internet facilitating document access from the World Wide Web, and version indicates the HTTP version used. Version 1.1 is the latest version of HTTP. The older versions of HTTP like the 1.0 and 0.9 are also in use. The URL is not limited to use in HTTP. It is a Web address defining where a resource is available. The URL in the request line defines the following: Method: The method protocol is used to retrieve a document. Some of the example method protocols are FTP and HTTP. Host: The Web server that stores the Web pages or the information to be published is called the host. The hosts are given alias names that usually begin with characters "www." Port: The Port number of the server is optional in the URL. If present, it is placed between the host and the path such that it is separated from the host with a sem