HyperText Transfer Protocol

An HTTP request consists of a request method, a request URL, header fields, and a body. HTTP 1.1 defines the following request methods:

• GET: Retrieves the resource identified by the request URL
• HEAD: Returns the headers identified by the request URL
• POST: Sends data of unlimited length to the Web server
• PUT: Stores a resource under the request URL
• DELETE: Removes the resource identified by the request URL
• OPTIONS: Returns the HTTP methods the server supports
• TRACE: Returns the header fields sent with the TRACE request

HTTP 1.0 includes only the GET, HEAD, and POST methods. Although J2EE servers are only required to support HTTP 1.0, in practice many servers, including the one contained in the J2EE SDK, support HTTP 1.1.

An HTTP response contains a result code, header fields, and a body. The HTTP protocol expects the result code and all header fields to be returned before any body content.
Some commonly used status codes include the following:

• 404: Indicates that the requested resource is not available
• 401: Indicates that the request requires HTTP authentication
• 500: Indicates an error inside the HTTP server which prevented it from fulfilling the request
• 503: Indicates that the HTTP server is temporarily overloaded, and unable to handle the request

See the Internet RFCs 1945 (HTTP/1.0) and 2616 (HTTP/1.1) : https://www.rfc-editor.org/rfc.html