TCP 3 way handshake

networks
TCP 3 way handshake

TCP starts a connection with a 3 way handshake to parse enough information to start the duplex communication:

  • The connecting host sends an empty synchronise message with the SYN bit set to 1. It sets the initial sequence for the messages this host will be sending client_isn.
  • The receiving host sends an empty synchronise-acknowledgement message with the SYN and ACK bit set to 1. It sets the initial sequence number for the messages this host will be sending server_isn with the acknowledgement header set to client_isn + 1.
  • Lastly the connecting host sends an empty acknowledgement message with the ACK bit set to 1. The acknowledgement header is set to server_isn + 1.