Procedure

The client initiates a connection with server by sending a TCP SYN packet.

The first SYN message contains a random number (Initial Sequence Number), unique to each new connection.

Step 1

To begin, enter a random four digit number here that will be used as the ISN to initiate communication.

The server responds with a SYN - ACK packet.

SYN indicates the random sequence number that the server will be using.

ACK is an acknowledgement to the client’s SYN and is calculated as clientSYN + 1.

Step 2

Enter a random number that will be SYN for the server.

Now, data packet transfer can begin. Try transferring a packet from the client to the server.

Step 3

Enter a random string to send to the server and observe the transfer and response.