Post by mil581 on Modbus TCP Server connection is ESTABLISHED but all holding registers are value 0? ^{CODESYS Forge talk (Post)}
Hello everyone! I'm facing a weird issue with CODESYS Control Win V3 x64 on a fresh Windows install. The situation is as follows: CODESYS Modbus TCP Server (Slave) is running and I can see live values in the mapping display of Modbus settings: GVL (e.g., 32, 42, 50). Port 502 is LISTENING according to netstat. When connecting via Modbus Poll or Node-RED, the connection status changes to ESTABLISHED and everything reports as fine. The Problem: Despite the successful connection, all holding registers return 0 no matter what. It's like the OS accepts the TCP handshake, the request counter goes up but the data payload never reaches Modbus Client (in this case Node-RED or Modbus Poll). Quick Stats: Firewall: Completely OFF. Unit ID: Verified & Matching. IP: Tried 127.0.0.1 and 192.168.0.1. Interface: Correctly bound in Ethernet Device settings. I already tried absolutely everything from changing IP address, subnet, port, deleting the project and starting new one and even nuking my old Windows install. Since I am near completion of my bachelor thesis only thing left for me to do is connect SoftPLC to NodeRED via Modbus but this issue is driving me crazy for weeks. I do not know what to do anymore.
Last updated: 2025-12-25

Post by thieulam on Codesys access to DICTIONARY OBJECTS of ethercat (CoE ) Servo Drive ^{CODESYS Forge talk (Post)}
Hello to all! How can I read or write, via my main code (ST), to the registers present in the DO of my ethercat CoE servo drive? These objects appear in the list of the INITIALIZATION page, and from here I can only access them at startup. How do I access it in run time from my main PLC_PROGRAM?
Last updated: 2024-06-19

Automatic parameter change with "Write all values" ^{CODESYS Forge talk (Thread)}
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write e txt file with SysfileWrite ( Need help) ^{CODESYS Forge talk (Thread)}
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CAA File: Read/write from shared folder or network drive. ^{CODESYS Forge talk (Thread)}
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Write variables of a structure inside another structure with pointers ^{CODESYS Forge talk (Thread)}
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Modbus TCP map read/write register to the same variable ^{CODESYS Forge talk (Thread)}
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Last updated: 2019-04-27

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