Lecture7TELNETProtocolHyperTextTransferProtocol.ppt

Example GET Request GET /~mgunes/cpe401/lab1.htm HTTP/1.1 Accept: */* Host: User-Agent: Internet Explorer From: mgunes@ Referer: / There is a blank line here! HTTP * HTTP Response ASCII Status Line Headers Section Content can be anything (not just text) typically an HTML document or some kind of image. Status-Line Headers . . . Content... blank line HTTP * Response Status Line HTTP-Version Status-Code Message Status Code is 3 digit number (for computers) 1xx Informational 2xx Success 3xx Redirection 4xx Client Error 5xx Server Error Message is text (for humans) HTTP * Example Status Lines HTTP/1.0 200 OK HTTP/1.0 301 Moved Permanently HTTP/1.0 400 Bad Request HTTP/1.0 500 Internal Server Error HTTP * Response Headers Provide the client with information about the returned entity (document). what kind of document how big the document is how the document is encoded when the document was last modified Response headers end with blank line HTTP * Response Header Examples Date: Wed, 30 Jan 2002 12:48:17 EST Server: Apache/1.17 Content-Type: text/html Content-Length: 1756 Content-Encoding: gzip HTTP * Content Content can be anything (sequence of raw bytes). Content-Length header is required for any response that includes content. Content-Type header also required. HTTP * Single Request/Reply The client sends a complete request. The server sends back the entire reply. The server closes it’s socket. If the client needs another document it must open a new connection. This was the default for HTTP 1.0 HTTP * Persistent Connections HTTP 1.1 supports persistent connections (this is the default). Multiple requests can be handled over a single TCP connection. The Connection: header is used to exchange information about persistence (HTTP/1.1) 1.0 Clients used a Keep-alive: header HTTP * Try it with telnet telnet 80 GET / HTTP/1.0 HTTP/1.0 200 OK Server: Apache ... Response Request-line Blank Line (end of headers) HTTP * Try it with telnet (persistent) tel