Tehnical Support

Telnet COM Port Control Protocol RFC-2217

Implementation Scenario

SENA Terminal Server products PS110, PS410, PS810, SS100, STS400, STS800 and STS1600 support a public protocol known as "Telnet COM Port Control Protocol," specified by IETF RFC 2217.

COM Port Control is an extension of the Telnet protocol, so it will only be available if the users try to connect to Sena Device Server using the telnet terminal that supports COM Port Control Protocol or Sena's COM Port Redirector, Serial/IP is configured to use Telnet.

During the connection attempt, the terminal or serial/IP will always request that the connection use COM Port Control. If Sena Device Server agrees to use COM Port Control, only then will it become active on the current connection to the Device Server. The Serial/IP redirector indicates a successful negotiation of COM Port Control by displaying three extra "lights" next to the active COM port name in the Port Monitor window.

The COM Port Control protocol includes a number of features. The set of protocol features that are supported have proven sufficient for nearly all applications with a need for some degree of port control.

SENA Terminal Server products PS110, PS410, PS810, SS100, STS400, STS800 and STS1600 with Tactical's Serial/IP redirectors use the COM Port protocol to provide the following port controls: 

• Baud rate (e.g., 9600)
• Data Length (e.g., 8 bits)
• Parity bit (e.g., none)
• Stop bits (e.g., 1 stop bit)
• DTR signal (often used to disconnect a call)

Serial/IP redirector use the COM Port protocol to report the following port conditions:

• DCD (signals that a call succeeded)
• DSR (signals that the modem is ready)
• RI (signals that the phone is ringing) .

For detailed information about this feature, contact us at