Introduction to HTTP protocol
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HTTP is a client-server protocol for transmitting hypermedia documents across the internet. It uses a request-response paradigm where clients make requests which are answered by HTTP servers. Requests use methods like GET and POST, and include headers. Responses contain status lines, headers, and content. HTTP allows caching, cookies, authentication, and redirects. It is the foundation of data communication for the World Wide Web via the hypertext transfer protocol.
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Introduction to HTTP protocol
- 1. Introduction to HTTP Aviran Mordo Head Of Back-End Engineering @ Wix @aviranm http://www.linkedin.com/in/aviran http://www.aviransplace.com
- 2. Intro • The Hyper Text Transfer Protocol (HTTP) is a client-server network protocol • In use by the World-Wide Web since 1990. • It is based on Request – Response Paradigm.
- 3. HTTP Request Message HTTP Method relative URL of the resource or a full URL HTTP Version GET /website/template/photography/ HTTP/1.1 Accept:*/* Accept-Language: en-gb Accept-Encoding: gzip, deflate User-Agent: Mozilla/4.0 (compatible; MSIE 6.0) Host: www.httpwatch.com Connection: Keep-Alive Head ers
- 4. HTTP Response Status line HTTP/1.1 200 OK X-Seen-By: sputnik3.aus_dsp X-Seen-By: s3.aus_pp Date: Wed, 21 Aug 2013 09:02:49 GMT Server: Apache cache-control: max-age=604800 cache-control: no-cache Pragma: no-cache Set-Cookie: _wixAB2=5371#5567#2014-03-19T14-27-00.000-0500|15711#3472#2014-08-13T11-01-00.0000500|14841#8565#2014-07-23T09-16-00.000-0500|15551#935#2014-08-11T07-55-00.000-0500|15451#3523#2014-08-07T0755-00.000-0500|14451#3267#2014-07-14T09-23-00.000-0500|15941#4497#2014-08-15T15-39-00.0000500|14951#8608#2014-07-28T07-24-00.000-0500|15861#7296#2014-08-15T10-02-00.000-0500|12891#3395#2014-06-23T0734-00.000-0500|13501#6547#2014-07-01T12-46-00.000-0500|15361#2985#2014-08-05T13-30-00.000-0500; Domain=.wix.com; Expires=Tue, 21-Aug-2018 14:06:39 GMT; Path=/ Set-Cookie: _wixCIDX=7e98f6cd-1c79-4661-9312-6f7aaeebf932; Domain=.wix.com; Expires=Mon, 17-Feb-2014 09:02:49 GMT; Path=/ Set-Cookie: _wixUIDX=10647958|1a2c4034-469d-4f4d-bbd9-17deddaf67ec; Domain=.wix.com; Expires=Mon, 17-Feb-2014 09:02:49 GMT; Path=/ Vary: User-Agent,Accept-Encoding Content-Language: en Content-Encoding: gzip double CRLF (carriage return, line feed) Content-Length: 8162 Content-Type: text/html;charset=UTF-8 Expires: 0 Cache-Control: no-cache Headers contents of the requested resource <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xmlns:og="http://ogp.me/ns#" xmlns:fb="https://www.facebook.com/2008/fbml" > <head> <meta http-equ
- 5. Everything is an extendable convention • You may create your own headers • You may create your own methods • You may not implement some methods • You may not implement header logic
- 6. HTTP Methods • GET method means retrieve whatever information. Is identified by the Request-URI • POST - used to send data to the server for updates. • PUT - method requests that the enclosed entity be stored under the supplied Request-URI. • DELETE - requests that the origin server delete the resource identified by the Request-URI. • HEAD - identical to GET except that the server MUST NOT return a message-body in the response. • TRACE - llows the client to see what is being received at the other end of the request chain and use that data for testing or
- 7. HTTP Headers • Accept: text/plain; - specify certain media types which are acceptable for the response. • Accept-Encoding: compress, gzip ; • Accept-Language: da, en-gb;q=0.8, en;q=0.7 ; • Cache-Control: max-age=0, must-revalidate • Vary: User-Agent,Accept-Encoding • ETag: "xyzzy" • Set-Cookie: _wixAB2=15361#2985#2014-08-05T13-30-00.000-0500 • Access-Control-Allow-Origin: * • X-Seen-By: sputnik3.aus_dsp • X-Wix-Dispatcher-Cache-Hit: no • X-Wix-Renderer-Server: apu2.aus.wixpress.com • X-Wix-Not-Found-Reason: Meta Site was not found
- 8. HTTP Status Codes and Errors • 1xx – Informational - intermediate response and indicates that the server has received the request but has not finished processing it. • 2xx – Successful: 200 OK • 3xx – Redirection: 301-permanent, 302-temporary • 4xx - Client Error: 400-bad request, 403-forbidden, 404-not found, 418 I'm a teapot • 5xx - Server Error: 500 Internal Server Error, 503-Service Unavailable,504-Gateway Timeout
- 9. Cookies Servers supply cookies by populating the set-cookie response header with the following details: Set-Cookie: name=value Name Name of the cookie Value Textual value to be held by the cookie Expire Date/time when the cookie should be discarded by the browser. s If this field is empty the cookie expires at the end of the current browser session. This field can also be used to delete a cookie by setting a date/time in the past. Path Path below which the cookie should be supplied by the browser. Domai Web site domain to which this cookie applies. n This will default to the current domain and attempts to set cookies on other domains are subject to the privacy controls built into the browser.
- 10. Type of cookies - Terminology • Session cookie - Web browsers normally delete session cookies when the user closes the browser • Persistent cookie - A persistent cookie will outlast user sessions – expires on a set timestamp • Secure cookie - A secure cookie has the secure attribute enabled and is only used via HTTPS • HttpOnly cookie - On a supported browser, only when transmitting HTTP (or HTTPS) requests. Not accessible to Javascript. • Third-party cookie - cookies that belong to domains different from the one shown in the address bar. Browsers send cookies via request header. Cookie: name=value; name2=value2 • Supercookie - cookie with an origin of a TLD(such as .com)
- 11. HTTP Caching • Preventing Caching - Cache-Control: no-cache (HTTP 1.1); Pragma: no-cache (HTTP 1.0) • Last-Modified: Wed, 15 Sep 2004 12:00:00 GMT – Browser can check the server for changes • GET /images/logo.gif HTTP/1.1 Jan 2038 19:14:07 GMT - browser can reuse Expires: Sun, 17 Accept: */* the content without having to check the server Referer: http://www.google.com/ Accept-Encoding: gzip, deflate If-Modified-Since: Thu, 23 Sep 2004 17:42:04 GMT User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;) Host: www.google.com HTTP/1.1 304 Not Modified Content-Type: text/html Server: GWS/2.1 Content-Length: 0 Date: Thu, 04 Oct 2004 12:00:00 GMT
- 12. HTTP Methods • GET - method is used to retrieve information from a specified URI and is assumed to be a safe, have no side effects repeatable operation by browsers, caches and other HTTP aware components. • GET can only supply data in the form of parameters encoded in the URI (Query String) or as cookies. Therefore, GET cannot be used for uploading files or other operations that require large amounts of data to be sent to the server. • POST method is used for operations that have side effects and cannot be safely repeated. • POST request message has a content body that is normally used to send parameters and data. Unlike using the request URI or cookies, there is no upper limit on the amount of data that can be sent
- 13. POST Request Method POST /httpgallery/methods/default.aspx HTTP/1.1 Host: www.httpwatch.com User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:23.0) Gecko/20100101 Firefox/23.0 Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 Accept-Language: en-US,en;q=0.5 Accept-Encoding: gzip, deflate DNT: 1 Referer: http://www.httpwatch.com/httpgallery/methods/ Cookie: __utma=1.1256977602.1377003403.1377082307.1377092487.5; __utmc=1; __utmz=1.1377003403.1.1.utmcsr=google|utmccn=(organic)|utmcmd=organic|utmctr=(not%20provided); __utmb=1.4.9.1377092850054 Proxy-Authorization: Basic b21lckB3aXguY29tOmg2M2ZycQ== Connection: keep-alive Content-Type: application/x-www-form-urlencoded Content-Length: 19 Set-Cookie: _wixAB2=5371#5567#2014-03-19T14-27-00.000-0500|15711#3472#2014-08-13T11-01-00.0000500|14841#8565#2014-07-23T09-16-00.000-0500|15551#935#2014-08-11T07-55-00.000-0500|15451#3523#2014-08-07T0755-00.000-0500|14451#3267#2014-07-14T09-23-00.000-0500|15941#4497#2014-08-15T15-39-00.0000500|14951#8608#2014-07-28T07-24-00.000-0500|15861#7296#2014-08-15T10-02-00.000-0500|12891#3395#2014-06-23T0734-00.000-0500|13501#6547#2014-07-01T12-46-00.000-0500|15361#2985#2014-08-05T13-30-00.000-0500; Domain=.wix.com; Expires=Tue, 21-Aug-2018 14:06:39 GMT; Path=/ double CRLF (carriage return, line feed) Set-Cookie: _wixCIDX=7e98f6cd-1c79-4661-9312-6f7aaeebf932; Domain=.wix.com; Expires=Mon, 17-Feb-2014 09:02:49 GMT; Path=/ Set-Cookie: _wixUIDX=10647958|1a2c4034-469d-4f4d-bbd9-17deddaf67ec; Domain=.wix.com; Expires=Mon, 17-Feb-2014 09:02:49 GMT; Path=/ post data / body Cache-Control: no-cache Headers Amount=10&B2=Submit
- 14. Redirection • HTTP allows servers to redirect a client request to a different location. Although, this will usually result in another network 30 round trip Permanent redirect – Content move permanently at the location specified by the Location header 1 and future requests should be directed to this location. 30 Temporary Redirect - future requests should still be sent to the original location 2 30 This status code was intended to be the only status code that caused a POST to be converted to a 3 GET. However, most browsers treat a 302 like a 303. 30 Not modified - Used in response to an If-Modified header to redirect a request to the browser's local 4HTTP/1.1 302 Found cache. Cache-Control: private,Public Content-Length: 162 Content-Type: text/html; charset=utf-8 Location: /httpgallery/redirection/default.aspx#example Set-Cookie: balance=990; path=/httpgallery/redirection/
- 15. HTTPS • The Secure Sockets Layer (SSL) was designed to encrypt any TCP/IP based network traffic and provide the following capabilities • Prevents eavesdropping • Prevents tampering or replaying of messages • Uses certificates to authenticate servers and optionally clients • The HTTPS protocol is the same text based protocol as HTTP but is run over an encrypted SSL session.
- 16. AJAX XML - Asynchronous JavaScript And • AJAX is a technology used by interactive web applications to make HTTP requests to a server without causing page transitions. • Requests have to go to the same domain as the page <script type="text/javascript"> function GetShoppingList() { // Create an instance of the HTTP request object var xmlHttp = new XMLHttpRequest(); // Specify HTTP GET by default and supply the relative url xmlHttp.open("GET", "getlist.aspx", false); // Start a synchronous AJAX request and wait for the response xmlHttp.send(null); var targetNode = document.getElementById("divShoppingList") ; // Use the HTML returned from server to create list targetNode.innerHTML = xmlHttp.responseText; }
- 17. Cross-origin resource sharing (CORS) • Allows JavaScript on a web page to make XMLHttpRequests to another domain • "preflighted" requests first send an HTTP OPTIONS method OPTIONS /resources/post-here/ HTTP/1.1 on the other domain, to determine if the request to the resource Host: bar.other request is safe to send. User-Agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; en-US; rv:1.9.1b3pre) Gecko/20081130 Minefield/3.1b3pre Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 Connection: keep-alive Origin: http://foo.example Access-Control-Request-Method: POST Access-Control-Request-Headers: X-PINGOTHER HTTP/1.1 200 OK Date: Mon, 01 Dec 2008 01:15:39 GMT Access-Control-Allow-Origin: http://foo.example Access-Control-Allow-Methods: POST, GET, OPTIONS Access-Control-Allow-Headers: X-PINGOTHER Access-Control-Max-Age: 1728000 POST /resources/post-here/ HTTP/1.1 Host: bar.other …
- 18. JSONP - "JSON with padding" • Provides a method to request data from a server in a different domain • JSONP has nothing to do with Ajax, since it does not use XMLHttpRequest. Instead it dynamically inserts Step 1 - You need to create a callback function. The function accepts some data. function w3r_callback(data){ console.log(data); } Step 2 - Include a script in your web page which contains the callback function created a step 1 as a parameter <script src="http://www.example.com?q=w3r_callback"><script> Step 3 - It outputs a script which calls the function and requested data is passed w3r_callback({ "FirstName" : "xyz", "LastName" : "abc", "Grade" : "A" } );