how does my web browser resolve Domain Names?

Question

I'm developing a network application which should be capable of contact DNS servers.

I was wondering what would be the best way to do it. And browsers came to my mind.

For example, how Firefox or Chrome resolve the Domain names i put in the URL bar?

I mean, i type http://www.google.com, how does it know that has to make a TCP request to the IP 209.85.195.104?

Thanks!

Answer 1

Here is a good comic that describes how your browser resolves host names:

http://www.labnol.org/internet/comic-how-browser-works/18086/

Your environment should be able to handle host name resolution for you. Is there a reason you would need to implement this yourself?

Answer 2

In the simplest scenario, browsers would use a function such as gethostbyname() to resolve names to addresses. However, this function is not always implemented in such a way that's convenient for a browser (it usually blocks until it gets an answer).

Browsers today are starting to use "DNS prefetch", where the browser will send DNS requests directly to a DNS server as the page is loading, to resolve addresses before the user clicks on the next link. That way, the user doesn't have to wait for name resolution when they click, and the browsing experience appears faster.