W5500 Datasheet, PDF (47/65 Pages) List of Unclassifed Manufacturers – Supports 8 independent sockets simultaneously

In these cases, Sn_SR is changed to SOCK_CLOSED.
Valid only in TCP mode.
Regardless of „TCP server‟ or „TCP client‟, the DISCON command
processes the disconnect-process („Active close‟ or „Passive close‟).
Active close: it transmits disconnect-request(FIN packet) to the
connected peer
Passive close: When FIN packet is received from peer,
a FIN packet is replied back to the peer.
0x08
DISCON
When the disconnect-process is successful (that is, FIN/ACK packet
is received successfully), Sn_SR is changed to SOCK_CLOSED.
Otherwise, TCP_TO occurs (Sn_IR(3)=„1)= and then Sn_SR is changed
to SOCK_CLOSED.
0x10
CLOSE
0x20
SEND
0x21 SEND_MAC
0x22 SEND_KEEP
cf> If CLOSE is used instead of DISCON, only Sn_SR is changed to
SOCK_CLOSED without disconnect-process.
If a RST packet is received from a peer during communication,
Sn_SR is unconditionally changed to SOCK_CLOSED.
Close Socket n.
Sn_SR is changed to SOCK_CLOSED.
SEND transmits all the data in the Socket n TX buffer. For more
details, please refer to Socket n TX Free Size Register (Sn_TX_FSR),
Socket n, TX Write Pointer Register(Sn_TX_WR), and Socket n TX
Read Pointer Register(Sn_TX_RD).
Valid only in UDP mode.
The basic operation is same as SEND. Normally SEND transmits data
after destination hardware address is acquired by the automatic
ARP-process(Address Resolution Protocol). But SEND_MAC transmits
data without the automatic ARP-process. In this case, the
destination hardware address is acquired from Sn_DHAR configured
by host, instead of APR-process.
Valid only in TCP mode.
It checks the connection status by sending 1byte keep-alive packet.
If the peer cannot respond to the keep-alive packet during timeout
time, the connection is terminated and the timeout interrupt will
occur.
W5500 Datasheet Version1.0 (August 2013)
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