Request and response

HTTP is an application layer protocol, and it is almost always used on top of TCP. The HTTP protocol has been deliberately defined to use a human-readable message format, but it can still be used for transporting arbitrary bytes data.

An HTTP exchange consists of two elements. A request made by the client, which asks the server for a particular resource specified by a URL, and a response, sent by the server, which supplies the resource that the client has asked for. If the server can't provide the resource that the client has requested, then the response will contain information about the failure.

This order of events is fixed in HTTP. All interactions are initiated by the client. The server never sends anything to the client without the client explicitly asking for it.

This chapter will teach you how to use Python as an HTTP client. We will learn how to make requests to servers and then interpret their responses. We will look at writing server-side applications...