tcp syn

[carl_townshend]

Hi all, when I make a connection to a server etc, is the first message a tcp syn, is this the handshake?

[padramas]

yes

[michael.leblanc]

It's the "first" packet of a "three-way" handshake.

1. Client sends SYN

2. Server sends SYN/ACK

3. Client sends ACK

It's used to synchronize sequence numbers, and to verify that each side received the other's message.

Tearing down a TCP connection is a four-way handshake.