what is TCP Half Open Connection and TCP half closed connection

Question

I am trying to understand what is the difference between TCP Half Open Connection and TCP Half closed connection can any one tell what exactly are they?

Answer 1

When TCP establishes a connection, it is considered guaranteed since there is a handshake that takes place:

1. The initiating computer sends the Connection request, sending a SYN
2. The responding computer grants the request, replying with a SYN-ACK
3. The initiating computer sends an acknowledgment, replying with an ACK

At that point the connection is established, and data begins to flow. In contrast, a UDP packet is not guaranteed, and is just sent in the hopes it gets there.

http://en.wikipedia.org/wiki/Transmission_Control_Protocol#Connection_establishment

Officially, according to the RFC's, a half-open TCP connection is when one side of the established connection has crashed, and did not send notification that the connection was ending. This is not the common usage today.

Unofficially, if can refer to an embryonic connection, which is a connection in the process of being established.

http://en.wikipedia.org/wiki/Embryonic_connection

Half-closed is the opposite of that unofficial definition. It is a state somewhere in the middle where the computers are tearing down the established connection.