Devices which allows companies to connect with RS232
, RS485 serial interface with the help of Ethernet LANs are called Terminal Servers. They can be simple devices with less or no security functionality features like data encryption or authentication. Main feature of Terminal Servers is to access network server applications not security. There are other Terminal Servers also which pay more attention to security, so that only authorized person can access servers. Whether the data shared over LAN is encrypted or not is also checked by these terminal servers. Initially Terminal Server was described as devices which can attach to serial RS232 devices like serial printers or green screen and transport the traffic through SSH, TELNET, TCP/IP or any other network protocol preferred by the user. Transfer of the traffic is done using an Ethernet connection.
Common Usage
RAW UDP socket connection: in order to be used with UDP based connection serial data for transport across UDP is converted by Terminal Servers is shared across multiple devices or point to point basis.
Back to Back Usage - this is specially designed for wiring problem. For example someone wants to replace a parallel line of modem network with their parallel Ethernet network, or users want to replace RS42, RS485 or RS232 wire and want to run their data over Ethernet without making any changes to the final serial device.
Console Management - Rev SSH, Rev Telnet: users can use SSH or Reverse Telnet to connect to a serial device. Terminal Servers in this application are also called as Console servers. They are called because of the reason that they connect to the console ports, found on the products like PBXs, servers and routers. They run SSH or Telnet on their PC and then attach to the Terminal Server in order to connect to their decisive serial device.
RAW TCP socket connection: Terminal Server can start a raw TCP connection. Again this can be on shared basis or point to point devices. User can start TCP sessions from the Terminal Server or from TCP server application.