What Is a URL Address? How Does It Work?

For many people, the primary purpose of going online is to surf the web. Although this is the predominant usage pattern, the web world and the internet actually have a very comprehensive and complex structure. Of course, people visiting a URL address on the web can read email and share files. However, the main purpose is to browse URL addresses or use the internet.

In the early days of the internet, the concepts of DNS and domain names did not exist. In those early days, in order to be able to share information, people had to memorise the IP addresses of the other computers. After that, we communicated by memorising computer names and using the hosts file. However, as the number of computers increased, this situation became negative. Memorising IP addresses on a network made up of hundreds or even thousands of computers joining together was simply not feasible. Remembering IP addresses and typing them in to surf the internet would have been very difficult.

Then this situation was resolved with domain names and the Domain Name System, which we call DNS. For example, to go to Google’s website, we began communicating by typing www.google.com.

When you want to visit a website, you communicate by typing the domain name. However, your computer or your ISP (such as TTNet, Turkcell, Turknet) needs to translate the URL address you typed into the browser into an IP address. This is because computers fundamentally communicate via IP addresses. At this point, communication is established by converting name servers to IP addresses through a protocol called DNS (Domain Name Service).

If the address for the domain name is found during this process, your browser sends a packet (using the HTTP protocol) to TCP port number 80. Thanks to an application on the target computer that listens for and responds to such requests (such as Apache, IIS, Nginx), communication is established by responding to your browser’s request.

What Is a URL Address?

Of course the same applies to https. However, in this packet communication, port 443 is used and the data sent and received is transmitted in encrypted form. Your browser decrypts the encrypted data with its key and displays it in your session. While it was previously used on the websites of sectors such as banking and shopping, in today’s internet world it has become widespread and the http protocol has given way to the https protocol.

This method is the operating principle of web pages. If you receive Error 404 for the page you want to go to, what you see is actually a message from your browser indicating that the web page you requested could not be found. Similarly, if you receive code 301, this indicates that the page has moved and your browser is redirected to the new address. If a 200 response is received, the relevant page exists and will be displayed in your browser.

The logic of emails is similar. It works in a similar way to visiting websites via URL addresses. When you send an email, your email client will look for the address of your email server. Your email client then uses POP3 to receive your incoming email or SMTP to send your outgoing email. Your email server (probably at your ISP or your company) first tries to resolve the address you sent to. For example, suppose you are sending an email to [email protected]. Your email server needs to translate this email address into an IP address for the email server at priviasecurity.com, and then your server sends your email there. Email transmission protocols such as POP3 and SMTP are also used during this sending process.

In today’s world, IMAP is widely used instead of POP3. Even if POP3 gives way to IMAP in the coming years, it will continue to be part of our lives. IMAP, the Internet Message Access Protocol, operates on port 143. The key advantage of IMAP over POP3 is that it allows the client to download only the email headers, after which the user can select which messages to download in full. This is particularly useful for smartphones and enables emails to be listed without loading fully, bringing speed and performance advantages.