Q: How can I secure access to a serial-to-Ethernet gateway on the local network?

On a closed industrial LAN, the serial-to-Ethernet gateway can be accessed via its static IP address. For security, you must: place the gateway on an OT VLAN isolated from the IT network, disable unused services (Telnet, unencrypted HTTP), use strong passwords for the administration interface, and filter access using an IP address whitelist. For access from the cloud or the WAN, always use a VPN.

Question 1

What is a Virtual COM Port (VCP), and how does it work?

Accepted Answer

A Virtual COM Port (VCP) is a software driver installed on a PC or server that creates a virtual serial port (COM5, COM6, etc.). This virtual port is actually a TCP tunnel to the serial-to-Ethernet gateway. The industrial application (SCADA software, configuration tool) believes it is communicating with a physical COM port, but the data actually travels over the Ethernet network. The VCP allows RS485 devices to be deployed far from the SCADA server without modifying the existing software.

Question 2

What is the difference between RS232 and RS485?

Accepted Answer

RS232 is an asymmetric (signal relative to a common ground) point-to-point serial connection, limited to 15 m and a single device. RS485 is a multipoint differential connection (two wires, A and B; signal = voltage difference), supporting up to 32 devices over 1,200 m with excellent immunity to electrical noise. RS232 is used for direct connections (printers, terminals, modems), while RS485 is used for industrial fieldbuses (Modbus RTU).

Question 3

What is the maximum baud rate supported on a serial-to-Ethernet gateway?

Accepted Answer

Most industrial serial-to-Ethernet gateways support baud rates ranging from 300 bps to 921,600 bps on RS232 and RS485 interfaces. The most common baud rates in industry are 9,600, 19,200, 38,400, and 115,200 bps. For long RS485 links (>500 m), it is recommended to limit the baud rate to 9,600 or 19,200 bps to ensure signal integrity.

Question 4

How many serial ports can a serial-to-Ethernet gateway support?

Accepted Answer

Serial-to-Ethernet gateways are available in 1-, 2-, 4-, 8-, or 16-port configurations, all housed in a single enclosure. For applications with many different serial devices (each on its own RS485 bus), an 8- or 16-port converter allows all connections to be consolidated onto a single network device. Each port can be configured independently as RS232 or RS485, with its own baud rate and Modbus configuration.

Question 5

Is DIN-rail mounting standard for an industrial serial-to-Ethernet gateway?

Accepted Answer

Yes, mounting on a 35 mm DIN rail (EN 60715) is the industry standard for control cabinets and electrical panels. Virtually all industrial serial-to-Ethernet gateways come with a built-in or optional DIN clip. This design makes it easy to install them in existing cabinets and to replace them without additional wiring. The power supply is typically 24 VDC, which is standard in industrial cabinets.

Question 6

Can Modbus RTU be converted to Modbus TCP using a serial-to-Ethernet gateway?

Accepted Answer

Yes, this is one of the most commonly used functions. The gateway receives Modbus TCP requests (port 502) from the Ethernet network, converts them to serial Modbus RTU, and sends them over the RS485 bus, then transmits the response back in the opposite direction. From the SCADA or monitoring side, the RS485 device appears as if it were directly connected via Modbus TCP, without any changes to the monitoring software.

Question 7

What is the latency introduced by a serial-to-Ethernet gateway?

Accepted Answer

The latency of a serial-to-Ethernet gateway is typically less than 5 ms for the protocol conversion itself. The total latency depends mainly on the serial baud rate (an 8-byte Modbus frame at 9,600 bps takes ~8 ms) and the Ethernet network latency (< 1 ms on a LAN). In total, a round-trip Modbus RTU → TCP transaction takes less than 30 ms on a local network, which is sufficient for all monitoring applications.

Question 8

How can I secure access to a serial-to-Ethernet gateway on the local network?

Accepted Answer

On a closed industrial LAN, the serial-to-Ethernet gateway can be accessed via its static IP address. For security, you must: place the gateway on an OT VLAN isolated from the IT network, disable unused services (Telnet, unencrypted HTTP), use strong passwords for the administration interface, and filter access using an IP address whitelist. For access from the cloud or the WAN, always use a VPN.

Criterion	Standard	Rugged Industrial
Power Supply	5–12 VDC	9–48 VDC or 100–240 VAC
Temperature	0°C to +55°C	-40°C to +75°C
Mounting	Desktop or rack	35 mm DIN rail
Connectors	Sub-D9 (DB9)	Removable screw terminals
Galvanic isolation	No	Yes (2,500 VDC)
ESD Protection	Basic	±15 kV
MTBF	~50,000 h	>100,000 h
Certifications	CE	CE, UL, ATEX (explosive atmospheres)

Industrial Serial-to-Ethernet Gateway — RS232/RS485 TCP/IP

Why Use an Industrial Serial-to-Ethernet Gateway?

Operating Modes

Virtual COM Port (VCP) Mode

Modbus RTU → TCP Mode (gateway)

Transparent Mode (TCP Raw)

UDP Mode

Technical Specifications to Check

Examples of Compatible Devices

Integration into an IIoT Architecture

Frequently Asked Questions

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Why Use an Industrial Serial-to-Ethernet Gateway?​

Operating Modes​

Virtual COM Port (VCP) Mode​

Modbus RTU → TCP Mode (gateway)​

Transparent Mode (TCP Raw)​

UDP Mode​

Technical Specifications to Check​

Examples of Compatible Devices​

Integration into an IIoT Architecture​