When testing a Siemens S7‑1200 PLC, I observed that the connection works perfectly in TLS (SSL)‑enabled mode – I can successfully connect and retrieve the complete symbol variable tree. However, when switching to non‑TLS (plain‑text) mode, the connection fails with an error.
The same client code and network configuration are used in both cases; only the security protocol setting is changed.
PLC Details (as shown in the attached screenshot)
| Property |
Value |
| Short name |
CPU1214CDC/DC/DC |
| Order number |
6ES7214‑1AG40‑0XB0 |
| Hardware version |
9 |
| Firmware version |
V4.6.0 |
| TIA Portal project version |
V18.0.1.0 |
| Rack / Slot |
0 / 1 |
| Installation date |
2025‑06‑01 14:07 |
| Manufacturer |
SIEMENS AG |
(Screenshot of the PLC info dialog is attached – see PLC_info.png)
Attachments
PLC_info.png – the diagnostic screenshot showing module and firmware details.
Environment
- TIA Portal V18 (update 1)
Thank you for any insights!
When testing a Siemens S7‑1200 PLC, I observed that the connection works perfectly in TLS (SSL)‑enabled mode – I can successfully connect and retrieve the complete symbol variable tree. However, when switching to non‑TLS (plain‑text) mode, the connection fails with an error.
The same client code and network configuration are used in both cases; only the security protocol setting is changed.
PLC Details (as shown in the attached screenshot)
(Screenshot of the PLC info dialog is attached – see
PLC_info.png)Attachments
PLC_info.png– the diagnostic screenshot showing module and firmware details.Environment
Thank you for any insights!