Alive Check Function - Mitsubishi Melsec-L Series User Manual

12.6

Alive Check Function

When the E71 has not communicated with the connected device for a certain period of time while the connection is
open, this function checks whether the connected device is alive by sending an alive check message to the connected
device and waiting for the response.
(1) Parameter setting
To enable the alive check function, select "Confirm" under "Existence Confirmation" in the open setting.
( Page 67, Section 7.1.4)
In TCP/IP communications, the following methods can be selected in the Ethernet operation setting. (
65, Section 7.1.3)
(2) Alive check method
The following alive check methods are available.
(a) Check using the PING command
This method is used for a connection opened using TCP/IP or UDP/IP. The E71 performs an alive check by
sending the PING command (ICMP echo request/response function) to the connected device with which
communications have not been performed for a certain period of time and waiting to see whether the response
*1
is received.
*1 The E71 automatically sends an echo response packet when it receives a PING echo request. (It sends a response to the
received PING command even if the connection used in the data communications with the connected device is closed.)
(b) Check using the KeepAlive function
This method is used for a connection opened using TCP/IP. The E71 performs an alive check by sending a
KeepAlive ACK message to the connected device with which communications have not been performed for a
certain period of time and waiting to see whether the response is received.
*2 The connection may be disconnected if the connected device does not support the TCP KeepAlive function (response to
a KeepAlive ACK message).
CHAPTER 12 OTHER FUNCTIONS
*2
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