TCP Three-Way Handshake
Step through connection establishment. Watch Sequence numbers and Acknowledgement numbers coordinate state.
Network Simulator
CLIENT
CLOSED
SERVER
LISTEN
Waiting to start...
Packet Details
LAST PACKET
---
SEQ NUM
---
ACK NUM
---
What's happening?
Step 1: SYN
Client wants to connect. Sends a SYN (Synchronize) packet with a random initial sequence number.
Step 2: SYN-ACK
Server acknowledges the client's SYN by adding 1 to the sequence number. Server also sends its own SYN with its own random sequence number.
Step 3: ACK
Client acknowledges the server's SYN by adding 1 to it. The connection is now established and data can flow.