State and the web
Written on 26 February 2017, 06:26pm
How do you get around the stateless nature of the web?
The HTTP protocol (along with other building blocks of the web, like IP and HTML) is stateless by design. This means that each connection is made up of a request and response, without any reference to earlier/later connections. “Users don’t log in to the Web, nor do they ever log out”. So without any intervention, each connection to a website (each page visit) is independent from the others.
How do you get around that?
Well, 3 possibilities, all of them using existing elements of the HTTP protocol:
1. HTTP Headers: cookies
2. HTTP URL: query string parameters
3. HTTP Body: POST (form) data
Important to note is that each of these can be altered (spoofed) by the client.
HTTP/2 is still stateless, but has some stateful components
HTTPS is stateless as well. Just because there is a TLS handshake at the beginning does not make the connection stateful. The stateful protocol is TLS, but HTTPS remains stateless, just as HTTP.
Example of a stateful protocol: FTP. “FTP has a stateful control connection which maintains a current working directory and other flags, and each transfer requires a secondary connection through which the data are transferred” (wikipedia)
Stateless: HTTP, HTTPS, IP
Stateful: TCP, TLS, FTP
How to send data from server to client over the web
1: Long polling the client polls the server; the server holds the request open until new data is available. Then the server responds and sends the new information. When the client receives the new information, it immediately sends another request.
2: Server Push – available in HTTP/2: client requests index.html, server responds with index.html but also with style.css and script.js, before the client parses index.html and asks for them
3. WebSockets (ws:// and wss://) – are a HTML5 feature aimed to address the request/response architecture of the web. There is an persistent connection between the client and the server and both parties can start sending data at any time.
– What really happens when you navigate to a URL
– Understanding the concepts of Transport Security Layer (TLS)
– How HTTP/2 will speed up your web browsing
– XKCD: Server Attention Span
– ColdFusion Book
– An Introduction to WebSockets
Currently, HTTP servers respond to each client request without relating that request to previous or subsequent requests; the state management mechanism allows clients and servers that wish to exchange state information to place HTTP requests and responses within a larger context, which we term a “session”. This context might be used to create, for example, a “shopping cart”, in which user selections can be aggregated before purchase, or a magazine browsing system, in which a user’s previous reading affects which offerings are presented.
Neither clients nor servers are required to support cookies. A server MAY refuse to provide content to a client that does not return the cookies it sends.
Written by Dorin Moise (Published articles: 260)