TCP Handshake Visualizer
Updated Mar 6, 2026
A step-by-step visual walkthrough of how TCP connections are established and torn down. Watch the SYN → SYN-ACK → ACK exchange animate in real time, then explore graceful close, reset, and simultaneous close scenarios.
Includes play/pause/step controls, adjustable speed, optional sequence numbers, a step-by-step log, and a quick-reference flag table. Great for students learning networking fundamentals or engineers who want a visual refresher.
Establishes a TCP connection between client and server.
Press Play or Step to begin.
Step Log
- Step 1: Client → Server: SYN— Client sends SYN to initiate a connection.
- Step 2: Server → Client: SYN+ACK— Server acknowledges and sends its own SYN.
- Step 3: Client → Server: ACK— Client acknowledges — connection established.
What You're Seeing
The 3-way handshake establishes a TCP connection. The client sends a SYN, the server replies with SYN+ACK, and the client confirms with ACK. Only after all three packets are exchanged can data flow in both directions.
| Flag | Meaning |
|---|---|
| SYN | Synchronize — initiates a connection |
| ACK | Acknowledge — confirms receipt |
| FIN | Finish — requests connection close |
| RST | Reset — immediately aborts connection |
| SYN+ACK | Server agrees to connect and acknowledges |
| FIN+ACK | Close request with acknowledgment |