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About Http Connection
- 2. HTTP network protocol • HTTP is a network protocol of the Web • Hypertext Transfer Protocol – Delivers resources on the WWW – Usually delivered by TCP/IP • HTTP client sends a request to HTTP server – Default port is 80 • Resource can be a file or dynamically generated query result (CGI, PHP …)
- 3. Structure of HTTP • Consists of request and response • Format – an iniPal line, – zero or more header lines, – a blank line, – opPonal message body (this is the resource) • Example – <initial line, different for request and response> – Header1: value1 – Header2: value2 – <optional message body>
- 4. IniPal Request Line • IniPal line is different for the request than response. • Request line has three parts – method name, local path to resource, version of hVp • Example – GET /path/to/file/index.html HTTP/1.0 • Method name can be GET, POST and HEAD
- 5. IniPal Response Line • The iniPal response line, called the status line • Typical status lines – HTTP/1.0 200 OK – HTTP/1.0 404 Not Found • Status code (200, 404) is computer-‐readable, reason phrase is human-‐readable • Status codes – 1xx, informaPon message – 2xx, success – 3xx, redirect – 4xx, client error – 5xx, server error • See all status codes – hVp://www.w3.org/Protocols/rfc2616/rfc2616-‐sec10.html
- 6. Header Lines • Header lines provide informaPon about the request and response – Header-‐name: value • HTTP 1.0 provides 16 headers, HTTP 1.1 46 headers • Client should tell who is making the request – From: – User-‐Agent: • Server should idenPfy – Server: – Last-‐modified:
- 7. Message Body • Message body contains the resource • Usually the message body includes header lines – Content-‐type: • MIME type of the resource, for example text/html, image/gif – Content-‐length • bytes
- 8. Sample Exchange KK605406LS-2:~ pohjus$ telnet www.jmarshall.com 80 Trying 192.220.73.220... Connected to www.jmarshall.com. Escape character is '^]'. GET /index.html HTTP/1.0 HTTP/1.1 200 OK Date: Mon, 18 Mar 2013 09:51:18 GMT Server: Apache/1.3.42 (Unix) mod_auth_tkt/2.1.0 FrontPage/5.0.2.2635 mod_ssl/2.8.31 OpenSSL/0.9.8r Last-Modified: Mon, 04 Feb 2013 20:21:01 GMT ETag: "1d697f5-9f3-5110182d" Accept-Ranges: bytes Content-Length: 2547 Connection: close Content-Type: text/html <html>
- 9. POST Method POST /path/script.cgi HTTP/1.0 From: myname@email.com User-Agent: Some-tool Content-Type: application/x-www-form-urlencoded Content-Length: 32 name=jack&age=22
- 10. Exercise 1. Use telnet to make a connecPon to site, see response 2. Use some live hVp extension in browser to see hVp informaPon 3. Make a HTTP GET to www.whaPsmybrowser.com. Fake your "browser".