Just a quick question, and probably a stupid one.
But usually when a client connects to an http server, the server sends them the header and the html, correct?
I'm packet sniffing a realtime-chat, and attempting to reverse engineer a plain text protocol, and it's connected to a http server. This is why I ask, for verification.
Basically, this is correct. Anyways, you have to differentiate between for example GET and POST Requests.
While POST Requests normally have a "real" body with information that they are delivering to the Server, the body of GET Requests is empty for most of the time.
For the responses, your Claim is correct. The Header is sent to tell how big the response is, which MIME Type is used, etc.
Related
When a web server receives a http(s) GET request from a client, it has access to some information such as:
The client IP
The request itself :
the headers (including the cookies)
the content
and... that's all ?
I am wondering if there is something else.
Indeed, I am trying to make a server that can access to a page where it can collect some information to update its database. The site denied access to my server but not to web browsers, even if I replicate the IP, the headers and the content.
Thanks for your help.
Yes, it's only what is contained in the request itself. The server cannot reach back to the client to "pull" information, it only has the information contained in the HTTP request and the underlying TCP/IP packet. That's:
the requesting IP address
the HTTP headers, including requested URL and HTTP method
the HTTP request body, if any
if it's HTTPS, any data exchanged during the TLS handshake, which is usually not very relevant for identifying anything significant
All of that information is voluntarily provided by the requesting client.
In developer.mozilla.org says:
HTTP headers allow the client and the server to pass additional
information with the request or the response
but I don't understand what is the use of that? What is the need to pass additional information with the request or the response?
This is a hard question to answer concisely because of the many different types of HTTP headers and what they do, but here's an attempt at a one-line answer:
HTTP headers allow a client and server to understand each other better, meaning they can communicate more effectively.
So then if you look at individual headers, it becomes clearer why each is needed:
User-Agent header
Sent by the client
Tells the server about the client's setup (browser, OS etc.)
Mostly used to improve client experience, e.g. tailoring responses for mobile devices or dealing with browser compatibility issues
set-cookie header
Sent by the server
Tells the browser to set a cookie
host header
Sent by the client
Specifies the exact domain name of the site the client wants to reach, this is used when a single server hosts multiple websites (a.k.a. virtual hosting)
I am curious to know the difference between the data sent over a HTTP connection and over HTTPS connection. I mean, what is the content, how it looks like in both cases. I am able for find for HTTP, but what is the corresponding content if same information is shared over HTTPS? HTTP contains Request Line, Header and Message body. I hope difference will be wrt Message body. Can anyone explain? Certificate content is embedded in this Message body or how is it?
In HTTPS (HTTP over SSL) the HTTP request is performed over a SSL tunel, hence both the HTTP headers and the payload are encrypted.
The certificate is sent by the server when the connection is established, as part of the TLS handshake. Such certificate must be trusted by either the client itself or a party that the client trusts.
Probably this article will give you a better understanding of the handshake.
I am curious to know the difference between the data sent over a HTTP connection and over HTTPS connection.
There is no difference.
I mean, what is the content, how it looks like in both cases.
It is the same in both cases.
I am able for find for HTTP, but what is the corresponding content if same information is shared over HTTPS?
It is the same.
HTTP contains Request Line, Header and Message body.
And so does HTTPS.
I hope difference will be wrt Message body.
The difference is in the fac that the entire payload is encrypted.
Can anyone explain?
I have endeavoured to do so.
Certificate content is embedded in this Message body
No.
or how is it?
It is embedded in the TLS handshake, which precedes any data exchange over the connection, including the entirety of any HTTP content.
I am able to consistently reproduce this problem where I request a URL from my server and I get back a 200 code but the response headers and response body are empty. If I monitor incoming traffic on my web server I never see the request come in. My web server sits behind a proxy server, if I monitor traffic there, I also do not see the request come in.
Any ideas as to where this empty response might be coming from, or tips as to what situations can result in an empty response like this?
This turned out to be a GET request size limit on our internal firewall proxy server. We were able to reduce the size at which we switch from a GET to a POST request in our code to avoid the limit.
I'm writing a web server, and I'd like to know what HTTP request headers (sent by the client) are the most common and thus that I should focus on implementing.
Right now, I only support Accept and Host.
Not sure on your scope but since you are interested in serving web browsers, you should have a look into the RFC (HTTP 1.1)
Read about what the server MUST process
The Cookie header might be a good idea, as would the Content-Length header; without Content-Length you won't be able to handle POST and PUT requests properly.