W5500 Datasheet, PDF (49/65 Pages) List of Unclassifed Manufacturers – Supports 8 independent sockets simultaneously

Sn_SR (Socket n Status Register) [R] [0x0003] [0x00]
Sn_SR indicates the status of Socket n. The status of Socket n is changed by Sn_CR
or some special control packet as SYN, FIN packet in TCP.
Value
0x00
0x13
0x14
0x17
0x1C
0x22
Symbol
SOCK_CLOSED
SOCK_INIT
SOCK_LISTEN
SOCK_ESTABLISHED
SOCK_CLOSE_WAIT
SOCK_UDP
Description
This indicates that Socket n is released.
When DICON, CLOSE command is ordered, or when a
timeout occurs, it is changed to SOCK_CLOSED regardless of
previous status.
This indicates Socket n is opened with TCP mode.
It is changed to SOCK_INIT when Sn_MR (P[3:0]) = „0001‟ and
OPEN command is ordered.
After SOCK_INIT, user can use LISTEN /CONNECT command.
This indicates Socket n is operating as „TCP server‟ mode
and waiting for connection-request (SYN packet) from a
peer („TCP client‟).
It will change to SOCK_ESTALBLISHED when the connection-
request is successfully accepted.
Otherwise it will change to SOCK_CLOSED after TCPTO
occurred (Sn_IR(TIMEOUT) = „1‟).
This indicates the status of the connection of Socket n.
It changes to SOCK_ESTABLISHED when the „TCP SERVER‟
processed the SYN packet from the „TCP CLIENT‟ during
SOCK_LISTEN, or when the CONNECT command is successful.
During SOCK_ESTABLISHED, DATA packet can be transferred
using SEND or RECV command.
This indicates Socket n received the disconnect-request (FIN
packet) from the connected peer. This is half-closing status,
and data can be transferred. For full-closing, DISCON
command is used. But For just-closing, CLOSE command is
used.
This indicates Socket n is opened in UDP
mode(Sn_MR(P[3:0]) = „0010‟).
It changes to SOCK_UPD when Sn_MR(P[3:0]) = „0010‟) and
OPEN command is ordered.
Unlike TCP mode, data can be transfered without the
connection-process.
W5500 Datasheet Version1.0 (August 2013)
49 / 65