The Hypertext Transfer Protocol (HTTP) is how web browser (client side) and web server (server side) communicate with each other.
Communication in terms of HTTP means requests and responses.
When you enter a URL in the address bar of your browser and hit enter, your browser requests the webpage connected with the entered URL. This is called an HTTP request.
That’s how such a
GET request can look like:
GET /index.html HTTP/2.0 Host: david.wolf.gdn
After sending such a request, DNS will be used to resolve the domain name
david.wolf.gdn to its IP address.
Once the IP address was found, Transmission Control Protocol (TCP) and Internet Protocol (IP) will be used to send the request to the host (
Once the initial requests find its way to the targeted host, HTTP is used to identify the requested file.
When the file was found on the host and everything is okay, an HTTP response is sent back to the client.
HTTP/2.0 200 OK Date: Tue, 23 Nov 2021 19:39:15 GMT Server: Apache/2.0.54 Last-Modified: Son, 21 Nov 2021 19:13:03 GMT Content-Length: 512 Connection: close Content-Type: text/html Content: <html>…</html>
The HTTP status code
200 in the first line of the HTTP response tells us that the requested file was found and everything is
At the bottom of the response, we are receiving the actual
<html>…</html>, of the file send by the web server.
In this case, it’s HTML code, as defined in the MIME-type
When the file is not found on the host, there is nothing that could be send back.
That’s when we receive an HTTP error
HTTP/2.0 400 Not Found
And that’s it for a short introduction into HTTP.
If I got you interested, there is plenty more to explore for you:
There are bunch more request methods, in this article you have seen a
GETrequest. There are other methods like
POSTto submit data using HTTP. And that’s not the end of the story, there are even more.
Same goes for HTTP response status codes, there are many more.
Have fun checking out the technology!