Precautions For The Socket Communication Function - Mitsubishi MELSEC L Series User Manual

6.3

Precautions for the Socket Communication Function

This section provides other precautions for the socket communication function.
(1) Port number
Because port numbers 0001
KNOWN PORT NUMBERS), it is recommended to use port numbers 0400
Do not specify 0014
Do not specify 007B
(2) Reading out received data
Read out received data when the Receive state signal (SD1286) has turned on.
Communication via the built-in Ethernet port may be affected if a considerable amount of received data have not
been read out for a long time.
(3) Conditions for closing
In TCP communications, even if no close request is sent from the connected device, the Open completion signal
will turn off to close the connection in the following cases.
• Alive check is timed out.
• Forced close is received from the connected device.
(4) Elements for TCP connection
The following four elements control TCP connections, and only one connection can be established with a unique
setting for these elements. To use multiple TCP connections at the same time, at least one of the four elements
must be different.
• IP address of the CPU module
• Port number of the CPU module
• IP address of the target device
• Port number of the target device
(5) Reestablishment of the same connection
Allow eight seconds or more before reestablishing a connection of the same target IP address, the same host
station port number, and the same target port number after closing it.
If the reestablishment is time-critical, it is recommended to change the host station port number on the Active
open side.
(6) Precautions for file access during communication
The CPU module will perform file access processing prior to Ethernet communication processing. Because of
this, processing of the socket communication function may be delayed if a file is accessed by FTP or a
programming tool during the processing.
When accessing a file while response time monitoring is performed on the connected device with the socket
communication function, add the time required for file access to the monitoring time.
to 03FF are assigned to the host station for use of major protocols (WELL
H H
and 0015 for the socket communication function when using the FTP function.
H H
for the socket communication function when using the time setting function (SNTP).
H
CHAPTER 6 SOCKET COMMUNICATION FUNCTION
to 1387 or 1392
H H
to FFFE .
H H
6
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