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FINS/TCP Method | Section |
7-4 FINS/TCP Method
7-4-1 Overview
FINS/TCP Features
The FINS/TCP method is a FINS communications method that uses the TCP/ IP protocol. TCP/IP is a
The FINS/TCP method has been newly added to the
For communications between a personal computer and a PLC, the computer should normally be set as the client and the PLC as the server. For communi- cations between two PLCs, either one can be set as the client and the other as the server.
Node
(Client)
Node
(Server)
Request to establish a connection
Connection established
Acknowledgement
Data transmission 1
Acknowledgement
An acknowledgement is received whenever a connection is established or data is sent, so transmissions are more reliable but somewhat slower.
Compared to the FINS/UDP method, the FINS/TCP method has the following characteristics.
•Data transmission is more reliable, due to factors such as retry process- ing at the TCP/IP layer. The FINS/TCP method is thus better suited to dealing with communications errors in an IP network that spans several layers.
•Remote clients can be restricted by means of settings at the server (i.e., the server can be protected from access by
•Broadcasting cannot be used.
•TCP/IP has various retry procedures, and this tends to lower its perfor- mance in comparison with UDP/IP.
•There is a limit to the number of connections that can be made (i.e., 16 connections maximum), and any given node can communicate only with up to 16 other nodes at a time.
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