APPX
Appendix 5 TCP/IP Communications, UDP/IP Communications
383
A
UDP/IP communications
This section describes the UDP/IP communications. Since UDP/IP communications does not establish a connection during
communication and does not check that the communication destination has correctly received the data, the line load is lower.
Note that the data reliability is lower than TCP/IP communications.
Communication flow
UDP/IP communications does not require a process to establish a connection with the external device as is required with
TCP/IP communications.
Wait at least 500ms or more before executing the open processing again after the close request is sent from
the external device to the Ethernet-equipped module.
Open procedure
The open/close processing procedure is as follows, according to the setting of "Opening Method" under "Own Node Settings"
in "Basic Settings". ( Page 242 Own Node Settings)
■When "Do Not Open by Program" is set
After the Ethernet-equipped module mounted station starts up, the UDP/IP communications setting connection automatically
opens, and data send/receive is enabled. Program for open/close processing is not required.
When the open/close processing is executed with a dedicated instruction from the Ethernet-equipped module,
even if "Do Not Open by Program" is set in "Opening Method" under "Own Node Settings" in "Basic Settings",
the open/close processing after a connection with the external device is established must be executed by the
program.
External device
Ethernet-equipped module
Server
Client
Open
Open
Receive processing (reading)
Data sending request
Data sending
The client opens
the port.
The client specifies
the destination and
sends data to it.
CloseClose
Receive processing (reading)
Data sending
Data sending request
The server requests
data reception and
reads the received data.
The client performs
the close processing.
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