stateless protocol and stateful protocol

问题:

How to understand stateless protocol and stateful protocol? HTTP is a stateless protocol and FTP is a stateful protocol. For the web applications requiring a lot of interactions, the underlying protocol should be stateful ones. Is my understanding right?

回答1:

Since you're asking about a Web application, the protocol will always be stateless -- the protocol for the Web is http (or https), and that's all she wrote.

I think what you're thinking of is providing a state mechanism in your Web application itself. The typical approach to this is that you create a unique identifier for the user's session in your Web application (a sessionID of one form or another is the common practice) which is handed back and forth between browser and server. That's typically done in a cookie, though it can be done, with a bit more hassle for you depending on your platform/framework, on the URL as well.

Your server-side code stores stateful information (again, typically called the user's session) however it wants to using the sessionID to look it up. The http traffic simply hands back the sessionID. As long as that identifier is there, each http transaction is completely independent of all others, hence the protocol traffic itself is stateless.

回答2:

HTTP is a stateless protocol, in other word the server will forget everything related to client/browser state. Although web applications have made it virtually look like stateful.

A stateless protocol can be forced to behave as if it were stateful. This can be accomplished if the server sends the state to the client, and if the client to sends it back again to the server, every time.

There are three ways this may be accomplished in HTTP:

a) One is cookies, in which case the state is sent and returned in HTTP headers.

b) The second is URL extension, in which case the state is sent as part of the URL as response.

c) The third is "hidden form fields", in which the state is sent to the client as part of the response, and returned to the server as part of a form's hidden data

SCALABILITY AND HIGH AVAILABILITY

One of the major reasons why HTTP scales so well is its Statelessness. Stateless protocol eases the replication concerns, as the state itself doesn't need to be stored on the server.

Stateful protocols are logically heavy to implement in Internet reliably. Stateless servers are also easily scalable, while for stateful servers scalablity is problematic. Stateless request can be sent to any node, at any time, while with Stateful this is not a case.

HTTP as Stateless protocol increases availability for stateless web applications, which otherwise would be difficult or impossible to implement. If there is connection lost, there is no state that is lost, simple request resend will resolve the problem. Stateless requests are also cacheable.

see more here

回答3:

http is a stateless protocol.all the web-based applications are stateless. when a request is send to the server a connection is established between client and server,the server will recieve the request ,processes the request and sends back the response.,and the connection is closed. if another request is sent then it will be treated as a new request,and new connection is established. in order to make http stateful. we use session management techniques. so that it uses the data coming from previous request while processing present request.i.e,it uses the same connection for a series of client server interactions. the session management techniques are: 1.hidden form field 2.cookie 3.session 4.url-rewriting;

回答4:

Your question is spot on, and yes, it would be great if your web transactions with your bank were done over a stateful connection. Alas, HTTP is stateless due to a quirky bug in FTP and a 12 socket limit in the partial socket table in BSD of 1989. Marcus Ranum explained it all here.

So HTTP throws away the state it inherits from TCP and has to recreate state at the application layer in the form of cookies. Crappy internet security is the result.

The Seif project proposes to fix all that using "secure JSON over TCP". DNS and certificate authorities are not required. The protocol and seifnode.js are finished and on github with an MIT license.

回答5:

HTTP doesn't 'inherit' from TCP, but rather uses it for a transport. HTTP uses TCP for a stateful connection, but then disconnects. Later it will connect again, if needed. So, while you browse through a web site you create many different connections. Each one of those connections is stateful, but the conversation as a whole is not, since you are dropping the connection with every conversation.

From this link

回答6:

Basically yes, but you have no choice but use HTTP which is where websites are served in. So you have to deal with compromises to make HTTP stateful, aka session management. Possibilities are basically passing on a session id through each call in the URL so you know when you're talking to someone you've talked about before, or via cookies, which achieve the same goal without cluttering the url. However, most modern web development languages take care of that for you; if you google for the language of your choice + "session management" you should get some ideas of how it's done.