Active Open Procedure; Open/Close Processing For Connection No.1 - Mitsubishi Electric MELSEC iQ-RJ71EN71 User Manual

Active open procedure

Active open is a connection method that performs an active open processing in respect to an external device (Passive open)
that is in a passive open standby state for a connection. The following figure shows the process for the Ethernet-equipped
module to Active open.
For OPEN/CLOSE instruction, refer to the following.
 MELSEC iQ-R Programming Manual (Module Dedicated Instructions)
Ex.

Open/close processing for connection No.1

Open status
Open enable status
(closed)
Closed status
'Initial status'
(Un\G1900024.0)
OPEN instruction
OPEN instruction
completion device
OPEN instruction
completion device +1
CLOSE instruction
CLOSE instruction
completion device
CLOSE instruction
completion device +1
'Open completion signal
(connection No.1)'
(Un\G1900000.0)
'Open request signal
(connection No.1)'
(Un\G1900008.0)
 After the module parameters are set, checks that the initial processing for the Ethernet-equipped module has completed normally. ('Initial status'
(Un\G1900024.0): On)
 Start the open processing using the OPEN instruction.
 The Ethernet-equipped module executes the open processing. (The module sends open request (SYN) to the external device.)
 Data can be exchanged after the open processing completes normally.
 Start the close processing using the CLOSE instruction. ('Open request signal (connection No.1)' (Un\G1900008.0): Off)
 The Ethernet-equipped module executes the close processing. (The module sends close request (FIN) to external device.)
 Data communication ends when close processing completes normally.
*1 If RST is returned from the external device after SYN is sent from the Ethernet-equipped module, open abnormal completion occurs
immediately, and the open processing ends.
*2 If ACK or FIN is not returned even after the TCP end timer time, the Ethernet-equipped module forcibly cuts off the connection (sends
RST). (Close abnormal completion)
*3 If the open processing target port has not been linked up, the OPEN instruction will complete with an error. Execute the open processing
again after link-up, or check that 'Connection status' (Un\G5192) is set to 1 before starting the open processing. If auto-negotiation fails,
the open processing will complete with an error. Retry the open processing after a while.
If the open processing completes with an error again, check the Ethernet cable connection or the operation of the external device and
switching hub.
APPX
380
Appendix 5 TCP/IP Communications, UDP/IP Communications
Parameter
communications
Power-on completed
Ò
*3
('Open request signal (connection No.1)' (Un\G1900008.0): On)
Ó
1 scan
Abnormally ended
Ö
ACK
SYN
Ô
SYN + ACK
Õ
*1
*2
1 scan
Abnormally
ended
ACK
FIN
Ø
×
FIN + ACK