Technical data

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Establishing a TCP connection
A connection is established using a handshaking procedure comprising of three steps:
… The client A sends a connection request with the SYN-bit enabled.
This allows the client to synchronise a sequence number with the
Server (B).
… Server (B) acknowledges (ACK) the client with its SYN-bit enabled
and with that the server has also synchronised its sequence number
with the client.
… Finally the client acknowledges with (ACK).
The transfer takes place with one or more bytes, which are numbered
and acknowledged.
A connection is terminated through the client (A) checking the local
TCP-packet and through all information being transferred and acknow-
ledged. A TCP-packet with the FIN-bit enabled is then sent. The server
(B) acknowledges this, but continues to send data if the application so
requires. Once this is complete the server (B) sends a TCP-packet with
the FIN-bit enabled.
AB
SYN
SYN Ack
Ack
Application
Transport
Network
Fysical
Application
Transport
Network
Fysical
B A C K