HTTP,Session & Cookies

ইন্টারনেট ব্রাউস করার সময় আমরা কোন একটা রিকুয়েস্ট সেন্ড করি আর সেই অনুযায়ী একটা রেসপন্স পাই।আমাদের ওয়েব ব্রাউজার থেকে আমরা রিকুয়েস্ট দেই তাই আমাদের কে বলা হয় ক্লায়েন্ট,আর যার কাছ থেকে রেসপন্স টা এক্সছেপ্ত করি তাকে বলা হয় সার্ভার।এখন,

prosno holo j kivabe data ta amader kache asbe?internet a data send ba accept korte client,server duijon kei kisu rule mane nite hoi,jate sohojei data transfer ba accept kora jai.Ai rule gula e hosse HTTP ba Hyper Text Transfer protocol.

HTTP stay kore application layer a. er thik nichei thake transport layer. Transport layer a thake TCP or UDP. HTTP

request ai protocol gula use kore.Bepar ta holo amn j HTTP just request ta create kore,niche kon layer koi ache se kisui janena,care o korena,se just jane j se akta request korse,er corresponding a tar oi requested data ta chai,kivabe seta asbe seta niye tar kono matha betha nai.Ai kaj ta kore transport layer. Application layer kisu port er sathe jukto thake ja jmn HTTP server port 80,SMTP server 25 etc. transport layer jkhn dekhe j port 80 a request asche se bujhe j aita akta HTTP request.

(details na jante chaile skip koro nicher part

transport layer jei kaj ta kore ta holo:

->packet a vag kore fele data k,jake segment o bole

->route thik kore kon dik diye gele joldi jaite parbe(jehutu segment a vag kora tai every segment alada alada route use korte pare)

->server side a jaye trasport layer data gula jehutu abar jora dite hobe tai segment er sathe header dite hoi j konta koto number segment,kar sathe k jora lagbe,kar pore k bosbe.

->asar somoi segment data kono change hoilo kina aita o check hoi error checking er maddhome.

trasport layer a thake TCP(Transmission Control Protocol) r UDP(User Datagram protocol).TCP hosse secure cause aita data thikmoto gelo kina tar jonno acknowledgement ferot nei.jodi acknowledgement na ase sei data ta nirdisto somoi por abar send kore .UDP te amn lagena,tai UDP faster kintu safe na.Online video gaming UDP er akta valo example.

er por Internet layer sob packet er samne akta kore ip address bosai dei,ja theke bujha jai j k data pathalo r ke data ta pabe. Then Network layer a arekta header mara hoi jar nam holo MAC address,soja banglai hardware information or address. Finally data ta physical or wave er maddhome send kora hoi.)

HTTP er important point:

1. HTTP akta stateless protocol. akbar kono site visit korar pore jkhn arekbar oi site tai visit kori tokhon ai bepare HTTP kisui janena j ageo oi site ta visit kora hoise kina,se purapuri new akta request generate kore. (aita k stateful korar jonno amra cookie r session use kore thaki).

2.HTTP use kore j kono rokomer data adan prodan kora jai,jotokhon both client and server computer ta except kore.

3.Data ana neyar jonno kon method use korbo ta bole dite hoi.Method er moddhe ase get,post,put,delete etc.Jmn HTTP request ta jodi get hoi tar mane amra just kisu data chai,post mane new kono object create kora,ba kono new data server a store korte chai etc.

4.Both client r server header use kore. header a host er nam,accepted file type,accept lang etc likha thake.

request and response have three states.Let us depict those things below:(images from https://www.youtube.com/watch?v=eesqK59rhGA)

Figure:HTTP request and response Processes

Session and Cookies: Cookies hocche olpo kisu information ja client side er browser a store kora thake,jkhn amra kono request send kori tkhn browser cookie soho request ta send kore. Session hosse user data er collection ja server side a store kora thake r protita collection er akta associate user o thake.

(https://stackoverflow.com/questions/6339783/what-is-the-difference-between-sessions-and-cookies-in-php.

Session cookie use kore. Cookie te store kora info diye Session er collection ta identify kora hoi.karon sudhu akta user er info toh r server a thakena.hazar hazar user theke kono specific user khujte cookie ta kaje lage. jmn example hisabe bola jai jodi kono supershop amake akta card dei identification er jonno seita hocche cookie. R tader nijeder pc te amar somporke ja likhe rakse(ami kon product kini,kon color besi nei etc etc.) seita holo Session. Ami nischoi aklai oi super shop a jai na.Onek customer e jai.So tader jonnow Session lage. Onek user er moddhe theke specific customer k khujte tkhn cookie ta use kore Session ta khuja hoi.

Sobsomoi j server side Session thake taw na.Kono kono khetre client er browser ai session set kora hoi jate khub fast data provide korte pare(jmn ruby on rails).but jehetu browser a khub besi space deina store korte tai ai kaj ta difficult.

(https://www.youtube.com/watch?v=64veb6tKTm0&t=24s)