Let's start with an example of our famous people Alice and Bob.
So here Alice is the client and Bob is server. Alice wants to establish a TCP connection with Bob.
- First Alice will send SYN data packet over the network to server Bob (Alice is trying to access www.google.com, so for that it will need to establish a connection with google's server on port 80/443 ). 1st way
- Bob's server must have port open which Alice is trying to access, and ready to initiate a new connection. if yes, Bob server will send an ACK+SYN packet back to Alice.- 2nd way
- Alice receives the SYN/ACK packet from the server and responds back with ACK packet and connection is established. - 3rd step.
I have captured the tcpdump output on Wireshark:-
SYN - 1st way
SYN-ACK - 2nd way
ACK - 3rd way
Connection Established!
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