Specifications

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2.3.2 Passive open/close processing
The Passive open puts the open request (connection request by Active open) from an
external device of the TCP/IP connection into the receive wait status.
The Passive open includes Unpassive open and Fullpassive open.
Both of them are passive open processings for the TCP connection.
Open system Description
Unpassive
Waits for receiving an open request (connection request) addressed to the
local station from any of all the devices connected to a network.
Fullpassive
Waits for receiving an open request (connection request) addressed to the
local station from the designated devices.
The processing of the Ethernet module varies depending on the setting value of the
initial timing ("Do not wait for OPEN", "Always wait for OPEN") in the operational
settings of GX Developer.
(1) When setting "Always wait for OPEN" in the operational settings
The Ethernet module system always puts the connection into the wait-for-OPEN
status.
(No sequence programs for the open and close processing are required.)
Parameter
communication
completed
SYN+ACK
FIN+ACK
FINSYN
Open status
Open ready status (closed)
(Active open acceptable)
Close status
Initial normal completion X19
Open completion signal
(Address: 5000
H)
Open request signal
(Address: 5002
H
)
Power-on
1)
2)
3)
4)
(*1)
Number Description
1)
After parameter communication, confirm normal completion of the Ethernet module initial processing.
(Initial normal completion signal (X19): ON)
After the initial processing is normally completed, the connection is placed in the open ready status and the Ethernet
module waits for receiving an open request from an external device.
2)
The Ethernet module starts the open processing upon receiving the open request (SYN) from the external device.
When the open processing is normally completed, the open completion signal (address: 5000
H… b0) turns on and data
communication is enabled.
3)
The Ethernet module starts the close processing upon receiving the close request (FIN) from the external device.
When the close processing is completed, the open completion signal turns off and the data communication is disabled.
4)
After the Ethernet module’s close processing is completed, the connection returns to the open ready status.
*1 An open request (SYN) received during the time from normal completion of
the initial processing to change to the open acceptable status generates an
error, and the Ethernet module sends a connection forced close (RST).