FINS/TCP Method | Section |
•If there is no response from the client when the
•If a command other than FINS FRAME SEND or CONNECTION CON- FIRMATION is received from the server, the connection will close after the FINS FRAME SEND ERROR NOTIFICATION command is sent.
Even if the connection is closed at the FINS/TCP client, requests continue to be made to the FINS/TCP server every few seconds to open a connection.
Note After the Ethernet Unit power is turned ON or the Unit is restarted, the IP address for the connection used as the FINS/TCP client is the remote IP address set under the FINS/TCP Tab in the Unit Setup.
To dynamically change the remote IP address (i.e., during CPU Unit opera- tion), execute the CMND(490) instruction in the ladder program and send a FINS command (FINS/TCP CONNECTION REMOTE NODE CHANGE REQUEST: command code 27 30 hexadecimal) to the Ethernet Unit.
Automatic Allocation
of FINS Node
Addresses
When the FINS message service is used, a FINS node addresses must also be allocated in the host application for communications. The FINS node addresses used by the host application are normally allocated in advance using fixed allocations. When the FINS/TCP procedure is used, however, the FINS node addresses used by the host application can be allocated automat- ically at the Ethernet Unit.
■Automatic Allocation Procedure
When exchanging FINS node addresses, node address 0 (node address not set) is used for the client. At the server that receives the information, a num- ber from the automatically allocated node addresses (default: 239 to 254) controlled by the server that has not established a connection is automatically allocated, and the FINS node address is sent to the client.
After exchanging the FINS node addresses, the client uses the allocated node address (default: 239 to 254) to create FINS frames (substituting the value allocated in SA1 of the FINS header).
Personal computer
(Client)
Example:
IP address C
FINS node address 0
Active open
Ethernet Unit
(Server)
Example:
IP address S
FINS node address B
Passive open
Connection request (C→S)
Connection established
Connection established 
Connection established
| FINS node address 0 sent |
Local node address sent | Remote node address received |
| FINS node address sent |
| Client: A |
Remote node address received | Server: B |
Local node address sent |
FINS node addresses exchanged
FINS frame sent | FINS frame sent | Normal data communications |
|
| |
| Full duplex communications |
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