Omron CS1W-ETN21 Application Examples, Responding to Computers with Changed IP Addresses

IP Addresses in FINS Communications Section 5-2

5-2-3 Application Examples

Responding to Computers with Changed IP Addresses

FINS/UDP Communications Method

With FINS/UDP, whether using the automatic conversion method (dynamic), the IP address table method, or the combined method, remote FINS node addresses and remote IP addresses in the internal table are changed after FINS messages are received. Therefore, even when a FINS command has been received from a personal computer (a DHCP client computer) for which the IP address is dynamically changed, a response can still be sent back to the computer (the DHCP client computer) from which the command origi- nated.

Personal computer (client)

IP address changed

(acquired from DHCP server when connected)

		FINS command sent
		IP address		FINS command		Ethernet
					Ethernet Unit
	IP address		FINS response
Response sent back to					(with fixed IP address)
changed IP address

FINS/TCP Communications Method

With FINS/TCP, FINS node addresses and IP addresses in the internal table are changed with each connection that is established. Therefore, even when a FINS command has been received from a personal computer (a DHCP client computer) for which the IP address is dynamically changed, a response can still be sent back to the computer (the DHCP client computer) from which the command originated.

Personal computer (client)

IP address changed

(acquired from DHCP server when connected)

				FINS command sent
				IP address		FINS command		Ethernet
							Ethernet Unit
			IP address		FINS response
							(FINS/TCP server; with
		Response sent back to					fixed IP address)
		changed IP address
Note	Automatic IP Address Setting by DHCP Service
	DHCP service is a method whereby a DHCP server collectively manages all

of the IP address in a network.

Nodes that are functioning as clients acquire IP addresses from the DHCP server whenever the system is started. Therefore, at a personal computer using the DHCP service, IP addresses may be different with each system startup.

DHCP service is mainly used for automatic settings in devices such as per- sonal computers that are used for client applications. Nodes used for server

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