HTTP with Non-Persistent Connections
Let’s walk through the steps of transferring a Web page from server to client for the case of non-persistent connections. Let’s suppose the page consists of a base HTML file and 10 JPEG images, and that all 11 of these objects reside on the same server. Further suppose the URL for the base HTML file is
Here is what happens:
- The HTTP client process initiates a TCP connection to the server www.someSchool.edu on port number 80, which is the default port num- ber for HTTP. Associated with the TCP connection, there will be a socket at the client and a socket at the server.
- TheHTTPclientsendsanHTTPrequestmessagetotheserverviaitssocket.The request message includes the path name /someDepartment/home.index. (We will discuss HTTP messages in some detail below.)
- The HTTP server process receives the request message via its socket, retrieves the object /someDepartment/home.index from its storage (RAM or disk), encapsulates the object in an HTTP response message, and sends the response message to the client via its socket.
- The HTTP server process tells TCP to close the TCP connection. (But TCP doesn’t actually terminate the connection until it knows for sure that the client has received the response message intact.)
- The HTTP client receives the response message. The TCP connection termi- nates. The message indicates that the encapsulated object is an HTML file. The client extracts the file from the response message, examines the HTML file, and finds references to the 10 JPEG objects.
- The first four steps are then repeated for each of the referenced JPEG objects.