Computer networks need a communication medium of which allows a computer, servers, wireless devices, and IoT to interconnect to send, receive or block data from flowing to the device’s own Network Interface Card (NIC). A device’s NIC is a unique hardware device that grants devices to either send or receive information through a physical medium, fiber, or copper or through wireless, Bluetooth, or radio wavelengths. The medium determines the circumstantial events that lead to successful communication between two devices. However, machines do not just start sending data to each other without a purpose; otherwise, devices would not know when the transmission is over or when it will begin. Therefore, protocols and ports were invented to indicate from the machine to the machine which method to use and over which internet port to conduct the communication. Protocols such as FTP (ports 20,21), DNS (port 53), HTTP (80), and SMTP (25) are essential ports to start learning to gain a solid understanding as to how computer networking operates at its most inner core.
These protocols have a corresponding port that, for the most part, never changes. For instance, port 80 is always used with HTTP but never with FTP. Therefore, computers will know when a connection is made over port 80 that a website or web service in inbound or outbound. How might a computer connect to a website such as Google? Without the help of DNS, the user would need to know Google’s search engine website by its unique IP address to use the search engine. However, Domain Name Service (DNS) translates domain names, such as Google.com, into an IP address that a user can type into the URL to connect to the desired website. Whereas, without DNS, a user would need to remember every IP address that they regularly, and that is not how we as humans work. We more easily remember names such as Google, Yahoo, Microsoft, or Apple.
What if you wanted to transfer data from one computer on your network to a different machine on the same network? You would use File Transfer Protocol (FTP) over port 20 or 21 to make the data transfer. The computer sending the data will reach out to the destination computer, indicating that it would like to send data. The receiving computer will respond, suggesting that it is open to receive the information. This involves a three-way handshake that is a TCP communication technique that validates that the communication was successful. However, more about TCP and a three-way handshake in a different blog.
What if you wanted to receive emails from people or organizations? You would open port 25, which it Simple Mail Transfer Protocol (SMTP). The protocol is meant for email communication from many sources and senders to allow transmission over the internet. The protocol is how most mail is sent and received from people who are interested in speaking with you. Additionally, this is one way that people use Phishing schemes to exploit unsuspected individuals, of which unintentionally download files or submit their login credentials. However, more on phishing in a different blog.
In conclusion, these protocols are essential for daily communication between machines. Additionally, theses protocols and ports are the most fundamental to learn first to ensure that you can understand the basics moving forward. Lastly, you can research more on the topics on your own. There are many sources of information on these ports and protocols that go into more depth on how they work. If you are interested in these topics, I highly recommend researching these topics on your own to find out more.