Remote Access to Industrial HMI: A Major Driver of Productivity
A HMI (Human-Machine Interface)—or HMI in English—is the touchscreen or control panel that allows the operator to interact with the industrial process. Siemens TP700/TP1500, Schneider Magelis GTO, Weintek cMT, Beijer X2: this equipment is found on virtually all modern machines and production lines.
Remote access to these HMIs opens up considerable possibilities:
- Remote troubleshooting: The support engineer sees exactly what the on-site operator sees
- Virtual training: Demonstrating the interface without having to travel
- Configuration audit: Verifying machine settings without interrupting production
- Customer support: Machine manufacturers can assist their customers in real time
HMI Remote Access Protocols: VNC and RDP Explained
VNC (Virtual Network Computing)
VNC is the standard protocol for remote screen access. It transmits pixels from the remote screen to the client and sends back mouse clicks and keystrokes. VNC uses TCP port 5900 (5900 for display 0, 5901 for display 1, and so on).
Benefits for Industrial HMIs:
- Compatible with Embedded Linux, Windows CE, and Windows IoT
- Resource-efficient—runs on HMIs with limited RAM
- Many VNC clients available (RealVNC, TigerVNC, UltraVNC)
- Image compression optimized for industrial interfaces with minimal animation
RDP (Remote Desktop Protocol)
RDP is Microsoft’s remote desktop protocol. It is available exclusively on full versions of Windows (XP, 7, 10, 11, Server). TCP port 3389.
Benefits for Industrial PCs:
- Better display quality and performance
- Native Windows integration
- Native TLS encryption
Compatibility by HMI Brand
| Brand | Model | Protocol | Configuration |
|---|---|---|---|
| Siemens | TP Comfort (KTP700/900/1200 Comfort) | VNC | TIA Portal > Device properties > Web server |
| Siemens | SIMATIC IPC (Industrial PC) | RDP + VNC | Native Windows |
| Schneider | Magelis GTU/GTO | VNC | Vijeo Designer |
| Schneider | Magelis iPC | RDP + VNC | Native Windows |
| Weintek | cMT (cMT3090, cMT3151…) | VNC | EasyBuilder Pro > System > VNC |
| Weintek | eMT (eMT3070, eMT3105…) | VNC | EasyBuilder Pro |
| Beijer | X2 Pro | VNC + RDP | iX Developer |
| Beijer | X2 base | VNC | iX Developer |
| Mitsubishi | GOT2000 | VNC | GT Works 3 |
| Omron | NA series | VNC | Sysmac Studio |
Architecture of Remote HMI Access via 4G VPN
The architecture is based on the same principle as that used for automated systems:
- The HMI is on the industrial local network with a static IP address
- The 4G VPN router (DIN rail, 24 V DC) is connected to the same switch
- The VPN tunnel provides access to the local network from outside
- The VNC client (RealVNC Viewer, TightVNC, etc.) connects to the HMI’s IP address on port 5900
From a security standpoint, the VNC must never be directly exposed to the Internet. Port 5900 must only be accessible through the VPN tunnel.
Configuring VNC on the Most Common HMIs
Weintek cMT
In EasyBuilder Pro, go to System Parameters > Remote Desktop. Check "Enable VNC Server," set a password, and select the port (5900 by default). After downloading, the VNC Server starts automatically.
Siemens TP Comfort (via TIA Portal)
In TIA Portal, select the HMI and go to Properties > Web server. Enable "Enable web server on this device" and "Enable VNC access." After compiling and uploading, connect via VNC on port 5900.
Schneider Magelis GTU
In Vijeo Designer, go to Target > Configuration > Remote Access. Enable the VNC Server and set the password.
Optimizing VNC Performance for 4G Access
For a smooth experience over a 4G connection, here are a few settings to adjust on the VNC client side:
- Tight or ZRLE compression: better compression for industrial vector interfaces
- 16-bit colors: cuts bandwidth in half without affecting the visual quality of industrial HMIs
- Partial updates: modern VNC clients send only the changed areas of the screen
- Disable the desktop background (for Windows-based HMIs): reduces unnecessary data transfers
In practice, with a decent 4G connection (>5 Mbit/s, latency <80 ms), remote access to an industrial HMI is very convenient for all troubleshooting and configuration tasks.