Using Google App Engine

Chapter 4. Sending Data to Your Application

So far we have looked a bit at HTML and CSS in the browser as well as at the Python programming language that we will use within the server.

In this chapter, we start to put it all together by looking at the HyperText Transport Protocol (HTTP) and how the browser interacts with the server. This interaction between the browser and server across the Internet is called the request/response cycle because the cycle of the browser making a request to the server and getting a response from the server happens over and over as we browse the Internet. The request/response cycle is the middle portion of Figure 4-1.

Figure 4-1. The request/response cycle

Making an HTTP Request

When you type a Uniform Resource Locator (URL) into the address box of your web browser and press Enter, you are asking your browser to retrieve a particular document somewhere on the Web. The URL http://www.dr-chuck.com/page1.htm can be broken down into three parts (as shown in Figure 4-2):

• The first part of the URL indicates which network protocol is to be used when your browser contacts the host and requests the document. Usually the protocol is either http:// or https://, indicating HTTP or secure HTTP, respectively. Sometimes you will see a URL that starts with ftp://, indicating that the File Transfer Protocol (FTP) must be used to retrieve the document.
• The second part of ...