HTTP: The Definitive Guide

Transactions

Let’s look in more detail how clients use HTTP to transact with web servers and their resources. An HTTP transaction consists of a request command (sent from client to server), and a response result (sent from the server back to the client). This communication happens with formatted blocks of data called HTTP messages , as illustrated in Figure 1-5.

Figure 1-5. HTTP transactions consist of request and response messages

Methods

HTTP supports several different request commands, called HTTP methods . Every HTTP request message has a method. The method tells the server what action to perform (fetch a web page, run a gateway program, delete a file, etc.). Table 1-2 lists five common HTTP methods.

Table 1-2. Some common HTTP methods

HTTP method	Description
GET	Send named resource from the server to the client.
PUT	Store data from client into a named server resource.
DELETE	Delete the named resource from a server.
POST	Send client data into a server gateway application.
HEAD	Send just the HTTP headers from the response for the named resource.

We’ll discuss HTTP methods in detail in Chapter 3.

Status Codes

Every HTTP response message comes back with a status code. The status code is a three-digit numeric code that tells the client if the request succeeded, or if other actions are required. A few common status codes are shown in Table 1-3.

Table 1-3. Some common HTTP ...