“Keep-Alive” means that if there is no real data between the chip and the peer for certain period, the chip will send “Keep-Alive” packet to peer to check whether the peer can reply this packet or not.
If the peer can reply, the peer is alive.
If the peer cannot reply, the peer is offline and the chip will go to timeout interrupt after the retransmission retry-count of “Keep-Alive” packet.
Once the timeout interrupt occurred, the chip will return to the server mode (Listening).
Note: The chip must send the real data to the peer system. Otherwise, the “Keep-Alive” mechanism doesn’t work.
This is the TCP/IP protocol standard, and is not WIZnet’s own specification.
thanks 
