HTTP a n d m e 

HTTP RUNS THE MODERN WEB* 

WHAT IS HTTP? 

Hypertext Transfer Protocol an application protocol for distributed, collaborative, hypermedia information systems 

Hypertext Transfer Protocol an application protocol for distributed, collaborative, hypermedia information systems 

Tim Berners-Lee & Team 

…Who Created Original HTTP HTML Associated technology for a web server Text-based web browser 

ALL ABOUT THE GIVE AND TAKE AKA THE REQUEST LIFE CYCLE 

Basic HTTP Request Life Cycle 

No content

GET / HTTP/1.1 Host: duckduckgo.com Content-Type: text/html Cache-Control: no-cache HTTP/1.1 200 OK Server: nginx Date: Thu, 24 Jul 2014 04:21:31 GMT Content-Type: text/html; charset=UTF-8 Content-Length: 9991 Connection: keep-alive ETag: "53d05a42-2707" Expires: Thu, 24 Jul 2014 04:21:32 GMT Cache-Control: max-age=1 Strict-Transport-Security: max-age=31536000 Accept-Ranges: bytes … 

GET / HTTP/1.1 Host: duckduckgo.com Content-Type: text/html Cache-Control: no-cache HTTP/1.1 200 OK Server: nginx Date: Thu, 24 Jul 2014 04:21:31 GMT Content-Type: text/html; charset=UTF-8 Content-Length: 9991 Connection: keep-alive ETag: "53d05a42-2707" Expires: Thu, 24 Jul 2014 04:21:32 GMT Cache-Control: max-age=1 Strict-Transport-Security: max-age=31536000 Accept-Ranges: bytes … 

METHODS TO MADNESS 

A Request Method is… the primary source of request semantics; it indicates the purpose for which the client has made this request and what is expected by the client as a successful result. 

3 & 5 Make Many GET POST HEAD HTTP/1.0 OPTIONS PUT DELETE TRACE CONNECT HTTP/1.1 

GET / HTTP/1.1 Host: duckduckgo.com Content-Type: text/html Cache-Control: no-cache HTTP/1.1 200 OK Server: nginx Date: Thu, 24 Jul 2014 04:21:31 GMT Content-Type: text/html; charset=UTF-8 Content-Length: 9991 Connection: keep-alive ETag: "53d05a42-2707" Expires: Thu, 24 Jul 2014 04:21:32 GMT Cache-Control: max-age=1 Strict-Transport-Security: max-age=31536000 Accept-Ranges: bytes … 

OFF WITH ITS HEADERS 

Examples Host User-Agent Accept Accept-Encoding Accept-Language Request Server Location Content-Type Expires Cache-Control Response 

Reasons for Headers Provide more information about the request/response context Make the request conditional based on the target resource state Suggest preferred formats for the request/ response Supply authentication credentials Modify the expected request processing 

GET / HTTP/1.1 Host: duckduckgo.com Content-Type: text/html Cache-Control: no-cache HTTP/1.1 200 OK Server: nginx Date: Thu, 24 Jul 2014 04:21:31 GMT Content-Type: text/html; charset=UTF-8 Content-Length: 9991 Connection: keep-alive ETag: "53d05a42-2707" Expires: Thu, 24 Jul 2014 04:21:32 GMT Cache-Control: max-age=1 Strict-Transport-Security: max-age=31536000 Accept-Ranges: bytes … 

SOCIAL STATUS (CODE) 

Five Main Groups 1XX Informational 2XX Successful 3XX Redirection 4XX Client Error 5XX Server Error 

GET / HTTP/1.1 Host: duckduckgo.com Content-Type: text/html Cache-Control: no-cache HTTP/1.1 200 OK Server: nginx Date: Thu, 24 Jul 2014 04:21:31 GMT Content-Type: text/html; charset=UTF-8 Content-Length: 9991 Connection: keep-alive ETag: "53d05a42-2707" Expires: Thu, 24 Jul 2014 04:21:32 GMT Cache-Control: max-age=1 Strict-Transport-Security: max-age=31536000 Accept-Ranges: bytes … 

GET / HTTP/1.1 Host: www.duckduckgo.com Content-Type: text/html Cache-Control: no-cache HTTP/1.1 301 Moved Permanently Server: nginx Date: Thu, 24 Jul 2014 04:30:31 GMT Content-Type: text/html Content-Length: 178 Connection: keep-alive Location: https://duckduckgo.com/ Expires: Thu, 24 Jul 2014 04:30:32 GMT Cache-Control: max-age=1 301 Moved Permanently

301 Moved Permanently

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nginx 

PUTTING IT ALL TOGETHER 

Wrapping Up Requests are made to servers. Responses are sent in return to clients. Methods note “type” of request Status codes note “type” of response Headers modify request/response All defined in HTTP specifications 

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