HTTP/0.9 is the first version of HTTP. This version was first written to comply with the exactions given by Tim Berners-Lee about the transport of HTML pages at the CERN. Therefore, he implemented very simple requests, that is to say only the one to get a document (the GET method)! We cannot but ask for a document; it is impossible to send "personal" data to servers.
Why HTTP/0.9? When Tim Berners-Lee invented this protocol, there was no version number. HTTP/0.9 got its number only when HTTP/1.0 was written (HTTP/1.0 is the first HTTP protocol described in a RFC) and it was decided that this new version would be called HTTP/1.0.
Example of HTTP/0.9 request
All HTTP/0.9 requests look like this one:
The requested document arrives straigth after the request has been received, and then the connection is closed by the server.
In HTTP/0.9, there is only the GET method. Everything is performed using this method, even sending
data to the server (the requested URI looks then like this:
Advantages of HTTP/0.9
HTTP/0.9 has some undeniable advantages: it does not rely on the transport layer (layer 4: TCP or UDP) and it can be used to carry any kind of documents. There is nothing more simple than HTTP/0.9.
The first drawback is that the connection between the client and the server is closed every time after the server has replied to a request. The consequences are the following ones:
HTTP/0.9 is also not able to manage caches. Document transfers are not optimised at all.
We can send data to a server only by using a specific GET request, and this limits the amount of data we can send; let's also notice that this data is written in the URI, not hidden or encrypted, so there are problems of confidentiality.
The user is aware of errors (he can see a weird web page), but the web browser does not know there is something wrong happened.
It is provided by HTTP/1.0.
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