![Accept:
– List of schemes which will be accepted by client
– <field> = Accept: <entry> * [,<entry>]
– <entry> = <content type> *[;<param>]
– <param> = <attr> = <float>
– <attr> = q / mxs / mxb
– <float> = <ANSI-C floating point >
– Accept: text/html
– Accept: audio/basic q-1
– if no Accept is found; plain/text is assumed
– may contain wildcards (*)](https://image.slidesharecdn.com/hypertexttransportprotocol-211210173721/85/Hyper-text-transport-protocol-11-320.jpg)
![User-Agent
• Software product used by original client
• <field> = User-Agent: <product>
• <product> = <word> [/<version>]
• <version> = <word>
• Ex.
– User-Agent: IBM WebExplorer DLL /v960311](https://image.slidesharecdn.com/hypertexttransportprotocol-211210173721/85/Hyper-text-transport-protocol-13-320.jpg)
Hyper text transport protocol
- 1. Hypertext Transport Protocol TEAM MEMBERS: Allu Harshita-34 P.Aishwarya -39 P.Hrudaya sai bhavani -47 M.Tejasri -18 P.Sowmya -17
- 2. HTTP • Hypertext Transport Protocol • Language of the Web – protocol used for communication between web browsers and web servers • TCP port 80 • RFC 2616
- 3. URI,URN,URL • Uniform Resource Identifier – Information about a resource • Uniform Resource Name – The name of the resource with in a namespace • Uniform Resource Locator – How to find the resource, a URI that says how to find the resource
- 4. HTTP - URLs • URL – Uniform Resource Locator • protocol (http, ftp, news) • host name (name.domain name) • port (usually 80 but many on 8080) • directory path to the resource • resource name – http://xxx.myplace.com/www/index.html – http://xxx.myplace.com:80/cgi-bin/t.exe
- 5. HTTP - methods • Methods – GET • retrieve a URL from the server – simple page request – run a CGI program – run a CGI with arguments attached to the URL – POST • preferred method for forms processing • run a CGI program • parameterized data in sysin • more secure and private
- 6. HTTP - methods • Methods – PUT • Used to transfer a file from the client to the server – HEAD • requests URLs status header only • used for conditional URL handling for performance enhancement schemes – retrieve URL only if not in local cache or date is more recent than cached copy
- 7. HTTP Request Packets • Sent from client to server • Consists of HTTP header – header is hidden in browser environment – contains: • content type / mime type • content length • user agent - browser issuing request • content types user agent can handle • and a URL
- 8. HTTP Request Headers • Precede HTTP Method requests • headers are terminated by a blank line • Header Fields: – From – Accept – Accept-Encoding – Accept Language
- 9. HTTP Request Headers – Referer – Authorization – Charge-To – If-Modified-Since – Pragma
- 10. From: • In internet mail format, the requesting user • Does not have to correspond to requesting host name (might be a proxy) • should be a valid e-mail address
- 11. Accept: – List of schemes which will be accepted by client – <field> = Accept: <entry> * [,<entry>] – <entry> = <content type> *[;<param>] – <param> = <attr> = <float> – <attr> = q / mxs / mxb – <float> = <ANSI-C floating point > – Accept: text/html – Accept: audio/basic q-1 – if no Accept is found; plain/text is assumed – may contain wildcards (*)
- 12. Accept-Encoding • Like Accept but list is a list of acceptable encoding schemes • Ex – Accept-Encoding: x-compress;x-zip
- 13. User-Agent • Software product used by original client • <field> = User-Agent: <product> • <product> = <word> [/<version>] • <version> = <word> • Ex. – User-Agent: IBM WebExplorer DLL /v960311
- 14. Referer • For Server’s benefit, client lists URL od document (or document type) from which the URL in request was obtained. • Allows server to generate back-links, logging, tracing of bad links… • Ex. – Referer: http:/www.w3.com/xxx.html
- 15. Authorization: • For Password and authentication schemes • Ex. – Authorization: user fred:mypassword – Authorization: kerberos kerberosparameters
- 16. ChargeTo: • Accounting information • Accounting system dependent
- 17. Pragma: • Same format as accept • for servers • should be passed through proxies, but used by proxy • only pragma currently defined is no-cache; proxy should get document from owning server rather than cache
- 18. Modified-Since: • Used with GET to make a conditional GET • if requested document has not been modified since specified date a Modified 304 header is sent back to client instead of document – client can then display cached version
- 19. Response Packets • Sent by server to client browser in response to a Request Packet
- 20. Status Header • “HTTP/1.0 sp code” • Codes: – 1xx - reserved for future use – 2xx - successful, understood and accepted – 3xx - further action needed to complete – 4xx - bad syntax in client request – 5xx - server can’t fulfill good request
- 21. HTTP Response Headers • Sent by server to client browser • Status Header – Entities • Content-Encoding: • Content-Length: • Content-Type: • Expires: • Last-Modified: • extension-header • Body – content (usually html)
- 22. Status Codes • 200 OK • 201 created • 202 accepted • 204 no content • 301 moved perm. • 302 moved temp • 304 not modified • 400 bad request • 401 unauthorized • 403 forbidden • 404 not found • 500 int. server error • 501 not impl. • 502 bad gateway • 503 svc not avail
- 23. Statelessness • Because of the Connect, Request, Response, Disconnect nature of HTTP it is said to be a stateless protocol – i.e. from one web page to the next there is nothing in the protocol that allows a web program to maintain program “state” (like a desktop program). – “state” can be maintained by “witchery” or “trickery” if it is needed
- 24. Maintaining program “state” • Hidden variables (<input type=hidden> • Sessions – Special header tags interpreted by the server • Used by ASP, PHP, JSP – Implemented at the language api level