Though, a COM port is not the only communication interface that supports serial data transmission, the term "serial port" is generally considered to refer to interfaces based on a common communication protocol RS-232. RS-232 stands for Recommended Standard 232, a communication protocol that allows an exchange of serial data between a computer and connected instruments.
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 used between two computers or between a computer and an external hardware.
A serial (COM) port is a physical interface for serial communication and has been an essential part of all computers for more than 30 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 support a full-duplex transmission (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 the 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 in the buffer 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.
Serial ports have been used for communication of various devices with computers and servers over the decades.
Here are some devices that have utilized serial port interface for communication:
To share a serial to LAN with the least effort, you will need a Serial to Ethernet Connector software. The app is very intuitive to use and requires almost no special knowledge:
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.
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.
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.
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.