Socket Services And Socket Status - Omron CS1W-ETN01 Operation Manuals

Using Socket Services with Socket Service Request Switches
15 14
–
m+9 to m+16

6-2-6 Socket Services and Socket Status

Area until a socket is opened again. Writing data to the DM Area, however, is not
synced with writing to the Socket Status Areas, and timing may vary somewhat.
13 12 11 10 9 8
– – – – – – –
Status in indicated in bits 0 to 3 using the 1-digit hexadecimal codes shown in the
following table.
Code Status
0 CLOSED
1 LISTEN
2 SYN SENT
3 SYN
RECEIVED
4 ESTABLISHED
5 CLOSE WAIT
6 FIN WAIT1
7 CLOSING
8 LAST ACK
9 FIN WAIT2
A TIME WAIT
When using socket services, it is important to consider the timing of the status
changes in the Socket Status Area. The diagram below shows a flowchart for
opening UDP.
7 6 5 4 3 2 1
– – – –
Connection closed.
Waiting for connection.
Active and waiting for SYN.
SYN sent and received.
Connection established.
FIN received and waiting for close.
Finished and FIN sent.
Finished and FIN exchanged. Waiting for
acknowledgement of FIN arrival.
FIN received and finished. Waiting for acknowledgement
of FIN arrival.
FIN arrival acknowledged. Waiting for FIN.
Finished and waiting for silence for twice the maximum
segment life (2MSL).
Section
0
TCP connection status
Meaning
6-2
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