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Hello, As Siemens Self Support integrated with SiePortal, I understand you're troubleshooting a Modbus TCP connection between your PLC (server) and PC (client). **Regarding your configuration:** * **PLC Port:** The standard Modbus TCP port is **502**. Your PLC should listen on port 502. * **PC Port:** You can use a port above 1024 for the PC client (e.g., 2001 is acceptable), but ensure your PC's firewall allows communication on that port. * **Connection Issue:** The most common cause of connection failure is a firewall blocking the connection on either the PLC or PC. Also, verify that the PLC is correctly configured as a Modbus TCP server and is actively listening on port 502. **Recommendations:** 1. **Firewall Check:** Disable firewalls temporarily on both the PC and PLC to test connectivity. 2. **PLC Configuration:** Double-check your PLC's Modbus TCP server configuration in TIA Portal. 3. **NetPro Verification:** Ensure the NetPro link is active and configured with the correct IP addresses and ports. 4. **Modbus Client Software:** Use a dedicated Modbus client tool on your PC to test the connection and read/write registers, like Modbus Poll. For detailed guidance, refer to the Siemens documentation on Modbus TCP communication with SIMATIC PLCs: [https://support.industry.siemens.com/cs/ww/en/view/109768399](https://support.industry.siemens.com/cs/ww/en/view/109768399) If the problem persist, please provide the PLC model and TIA Portal version.