How to share Serial port over LAN

We'll dedicate this article to serial ports and sharing of serial to LAN. We'll talk about serial ports in general, what they are usually used for, and of course how serial over LAN works.

COM port definition

In general there are two forms of data transmission – serial and parallel. Parallel was invented pretty recently and although way faster than serial, it is not always as practical as the latter, especially with long distances in mind. Serial communication is usually between two computers or between a computer and an external device in a distance.

A serial (COM) port is a physical interface for serial communication and has been an essential part of all computers for more than 20 years. Even though USB interface is so vastly popular these days, serial ports are still a big part of industrial automation systems, scientific instruments, point of sale systems, etc.

As serial ports can work both ways - send to or receive data from devices - devices connected to them can send and receive data simultaneously.

A special controller chip - the Universal Asynchronous Receiver/ Transmitter (UART) - is used to ensure proper functioning of the ports. It receives the parallel output of computer's system bus and then transforms it into serial form. UART chips most often feature a special built-in buffer for caching data from the system, while it is being processed to be sent to COM port. Data they buffer serial over LAN can be from 16 to 64 kilobytes. Most of serial ports transfer data at 115 Kbps, while higher speed serial ports can reach the speed up to 460 Kbps.

COM ports usage

Serial ports are used for communication of various devices with computers and servers.

Some of the devices using serial port interface:

• Computer mouse. If a computer doesn't have PS/2 or USB port then a serial port is used to connect a mouse;

• Printer. Older models of printers and plotters;
• Modem. Sometimes it turns out to be easier to connect modem to serial port even if a computer is equipped with a USB one;

• Telecommunication equipment. Nothing more convenient for debugging, studying the boot up messages, kernel upgrading, and Ethernet connection troubleshooting;
• Temperature measuring device. A device like that connects only via RS-232 ports;
• Credit card readers;

• And even more.

Share COM port over LAN

To share a serial to LAN easily you'll need a Serial to Ethernet Connector software. It is very easy to use:

1. Download Serial to Ethernet Connector from here to install on a computer with a serial port to share and also on a computer that will access the port.
2. On a computer with the port to share choose the Server connection in Serial to Ethernet Connector. After customizing the settings click “Create connection” in Main window.

3. Open local COM port.
4. On another computer that will be connecting to the shared port create “Client” connection. Make sure that remote hostname and port number are the ones you've set in server machine configuration.

5. Click 'Connect' on the remote computer and access the shared port with device as if it was connected directly to the computer you are working with.

Here you go - access serial over LAN in the software interface and manage it like it's plugged directly to your local machine. You don't need any additional settings or harware.

Hardware solutions

Hardware solutions for sharing a serial port over LAN are called Terminal Servers, Device Servers and Console Servers. Read further to see what those are.

Terminal Servers

These allow connecting devices with RS232, RS422 or RS485 to Ethernet networks.

Terminal servers can be very simple devices not offering any security, such as data encryption and user authentication.

Device Servers

Ethernet LAN is used to interconnect sensors, instruments, machine tools, restaurant appliances, POS terminals and others. In the mid-1990s the first "device server" was created and converted serial transmission to Ethernet, letting serial-based devices communicate over a LAN instead of dedicated cabling. And even though newer devices have Ethernet ports, legacy devices still feature serial ports.

Console Servers

Most commonly, a console server provides a number of serial ports that are connected to the serial ports of other equipment. With console servers switching devices is smooth, authentication and encryption are available. Console Servers provide secure remote access to Unix, Linux, Windows Servers and any device on the network with a console port.

The consoles of the connected devices can be accessed by connecting to the console server over a serial link such as a modem, or over a network with terminal emulator software.

Please feel free to post questions in the comments.