Perle Systems Technical Notes
What is Serial Tunneling?
Serial tunnelling can be described as:
- Extending a serial (RS232, RS422 or RS485) link across Ethernet.
- Encapsulating asyncronous serial data from devices like scanners, card readers and POS terminals over Ethernet.
- Encapsulating serial data from industrial devices like RTU’s or PLC running ModBus, DNP or other protocols over Ethernet.
- Installing a serial to Ethernet Device Server on one end of a LAN, and another somewhere else on the LAN, to get RS232 data across town.
The bottom line is: Serial Tunneling enables you to establish a link across Ethernet to a serial port on another Serial Device Server. The serial data is packetized in both directions into Ethernet TCP/IP packets. This packetizing allows a user to connect a Serial Device Server to an existing serial device and have the communications go over Ethernet to another device without any changes to critical network applications.
Let's look at an example. One Serial Device Server can be connected to the serial port of a computer running a critical application in a central office or datacenter. The second Serial Device Server will be connected to the serial port on a Data Acquisition device located across town. When each Serial Device Server has a LAN connection and power is applied, communications between the two dedicated Device Servers automatically start a session.
Simply put, once the two Serial Device Servers are used in Serial Tunneling mode they automatically transfer serial data across the LAN as if it was transparent. The application on the central computer only opens the COM port and sends data out.
The fact that the Serial Tunneling feature makes the LAN transparent makes additional applications feasible. A card reader can send data to a display or a positioning camera can send information to a controller on a manufacturing line.
Data transmitted by one serial device is encapsulated and sent over Ethernet to the other device server. There the encapsulation is removed and then transferred to the other serial device.
When choosing a Serial Device Server that supports Serial Tunneling, Perle IOLAN Device Servers offer the widest range of high performance, low costs options on the market. All Perle IOLAN Device Servers support the tunnelling of raw serial data across Ethernet.
IOLAN Secure Device Servers also support encrypted tunneling through an IPSec VPN infrastructure.