TCP Lab - Free Online TCP Handshake Visualizer | IconVault
Watch the TCP 3-way handshake, data transfer and teardown as an animated packet exchange with state machine. Free, in your browser.
TCP Lab
Watch the TCP handshake, data transfer and teardown animate
CLIENT STATE MACHINE
SERVER STATE MACHINE
5 of 5 free copies left - everything runs locally in your browser.
Client
SYN_SENT
Server
LISTEN
SYN
seq=1000 - ack=-
Step 1. Client picks a random initial sequence number (ISN) and sends SYN. It now waits for a reply.
Full sequence
Simplified model: retransmission, congestion control, window scaling and simultaneous close are omitted. States shown: CLOSED, LISTEN, SYN_SENT, SYN_RCVD, ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT, LAST_ACK, TIME_WAIT.
About this tool
IconVault's TCP Lab turns the TCP connection lifecycle into an animated packet exchange you can step through: the 3-way handshake (SYN, SYN-ACK, ACK), data transfer with sequence numbers, and connection teardown with FIN packets. Each step shows the live state machine on both sides (LISTEN, SYN_SENT, ESTABLISHED, FIN_WAIT and more) with plain-language notes explaining what every packet does.
You can play, pause, step forward and backward, and reset the animation, which makes it ideal for networking students, interview prep and anyone who wants to finally understand sequence and acknowledgment numbers. It is free, runs fully in your browser, and the walkthrough is a faithful simplified model rather than a live packet capture.
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