A Guide to Serial Terminal Servers: Secure Remote Access to a Serial Port

A Serial Terminal Server is a software or hardware solution designed to make a non-networked serial-based peripheral with RS232, RS422, or RS485 interface accessible over LAN, Ethernet, or Wi-Fi. A typical hardware serial port terminal server is a small minimalistic gadget that has a serial port, a network port, and a very basic feature set.

A serial port terminal server (also known as serial console terminal server, terminal server, serial server, or Serial over Ethernet) is the most reliable and price-performant tool you can use to operate all your serial-based peripherals remotely over a wired or wireless network.

Technically, it’s an app or a gadget that serves as an intermediary between, on one end, a printer, a programmable logic controller, a cashpoint machine, or any other serial device that doesn't come with an in-built network adapter, and, on another end, Ethernet, LAN or WAN. It works both as a virtual serial port, and as a converter that reorganizes serial data as TCP/IP packets and vice versa so you can access and operate your serial devices remotely.

Connecting a device to a terminal server serial port instantly makes it accessible over the network. Opting for a software solution, you’ll also get reliable data protection with high-end encryption technology and a solid user authentication mechanism to secure your equipment against unauthorized access.

Serial to Ethernet Connector by Electronic Team is the fastest and easiest way to create a terminal server connection. Here’s what you’ll need to do to make this work:

Install the Windows serial terminal server program app (or a Linux serial terminal server) on a machine physically connected to your serial devices.

Configure the app on your local PC or laptop. To make a connection, this app uses a virtual COM port that fully emulates a real port your serial device is plugged into.

From that point on, you’ll be able to use and control the remote serial device as it was attached to your local machine directly.

Cisco Serial Terminal Servers are the high-end big-ticket devices mostly used by corporate giants. The most popular models are 2511 and 2509 (both are out of production).

Cisco 2509 has 8 asynchronous COM ports (2511 has 16 of those) you can use to connect up to 8 (or 16, for 2511) serial peripherals and then either access them from console ports or remotely from the access server via Telnet.

MOXA Terminal servers are also in demand due to high operating reliability, add-on security, and some nice bonus features, s.a. backup support, routing technology, and advanced encryption protocol. These servers are very durable, easy-to-use, and fit in well with security-sensitive equipment like cash registers, POS devices, routing gateways, etc.

The most popular product by DIGI is a one port serial port terminal server (owing to its low price), but there are also models with 2, 4, 8, 16, and 32 ports. These servers are compatible with all popular serial peripherals, have TCP and UDP sockets, and support the RealPort driver. For extra projection, you can enable TLS, SSL, or SSH encryption. Instead of the standard RS-232 version, you can opt for MEI-selectable RS-232/422/485.

Another well-used terminal server is serial Perle IOLAN. Key selling points of IOLAN servers are native support for IPv6 and cutting-edge TrueSerial® Technology for extra smooth communication.

Along with SSH/SSL encryption, the connection will be protected with the AAA security system, so it’s totally safe to use these servers for out-band remote access to card readers, PBX and POS terminals, or any other devices from any spot on Earth. Plus, you won’t have any trouble integrating it into your corporate net system.