The TCP Handshake

Lesson 17 of 32 in Coddy's The OSI Model course.

TCP promises that bytes arrive complete and in order. That promise starts with a ritual: before any data flows, the two sides perform the three-way handshake.

The client sends SYN: "I want to talk, here is my starting number."
The server answers SYN-ACK: "Heard you, I want to talk too."
The client confirms with ACK, and the connection is open.

Every TCP connection on Earth, every web page, every SSH session, begins with exactly these three packets.

Challenge

Beginner

Print the three handshake steps in order, one per line, exactly as written in the theory.

Expected output:

SYN
SYN-ACK
ACK

Try it yourself

Terminal

All lessons in The OSI Model

1Why Layers

The Layering Idea Seven Layers Numbers and Names Recap - The Stack

4The Network Layer

IP and TTL Ping and ICMP Routing Tables Recap - Layer Three

7Encapsulation

Wrapping Data Headers Everywhere Reading a Capture Recap - Follow the Wrap

2The Physical Layer

Bits on a Wire How Long Will It Take Duplex and Collisions

5Transport: TCP and UDP

PortsThe TCP HandshakeTCP vs UDP Sockets in Action Recap - Layer Four

8The Journey of a Packet

A Click Happens Crossing the Networks Arriving and Climbing Recap - End to End

3Data Link and MACs

Frames and MACs Reading a MAC ARP Recap - Layer Two

6The Upper Layers

Session and Presentation The Application Layer Watching the Layers Recap - Top of the Stack

Practice on your own: Terminal playground