The TCP Protocol: TCP stands for Transfer Control Protocol, and it’s like the foundation of the Web and other things we use, like Email.
It was first defined in a document called RFC 793 way back in 1981, making TCP one of the oldest parts of the Internet.
Imagine it like a stack of building blocks – TCP is one block on top of another important one called the Internet Protocol (IP). Together, they help make sure that when you send something over the Internet, it gets to where it’s supposed to go.
On top of TCP, there are other protocols that handle specific tasks like showing web pages (HTTP), transferring files (FTP), or managing emails (IMAP), among many others.
Now, here’s the cool part: TCP, unlike IP and UDP, is like having a proper conversation. It’s connection-oriented.
Before we can send anything over TCP, we need to say, “Hey, are you there?” and wait for the other side to say, “Yes, I’m here!” This sets up a connection. Then, we can send little packages of information back and forth. Once we’re done talking, we say, “Goodbye,” and close the connection. It’s like having a nice, organized chat over the Internet.
When we send data using TCP, there’s a kind of intricate process called a handshake that needs to take place.
I won’t get into all the nitty-gritty details, but this handshake is like a special greeting that ensures both ends of the connection agree to talk to each other. This is important because it sets up a reliable connection.
Here’s the cool part: With TCP, we can always check if a piece of information sent by the sender made it to the receiver correctly. It’s like making sure your friend got your message without any mistakes – TCP ensures that the data is sent and received accurately.
If a piece of information (packet) goes missing during the trip, TCP can handle it. It’s like if you lost a letter, you’d send it again to make sure your friend gets it.
Now, in the IP protocol, connections are between whole computers. But in TCP, it’s more like one application on a computer talking to another application on a different computer. They use something called ports to do this.
Think of a port like a special door for a specific application on a computer. For Examples:
- localhost:8080 means the application is on your own computer, using port 8080.
- google.com:1234 means it’s talking to an application on Google’s computer, using port 1234.
Each type of application has a special door number called a port. It’s like HTTP (web pages) usually uses door 80, HTTPS (secure web pages) uses door 443, and FTP (file transfers) uses door 21. That’s why when you visit a website in your browser, you don’t usually need to say the door number.
However, programs don’t have to use the default doors. Especially on your own computer, you might see doors like 1313 or 8080 when you start a new application.
These door numbers can be anywhere from 1 to 65535. It’s a big range – like having lots of doors in a huge building. The actual number is like a code that helps the computers know which application they’re talking to.
