How can I talk to a serial (COM) port from the command line/batch file?

A. NT is a model of inconsistency when it comes to redirecting stdin and stdout. You can redirect console output to a serial port easily, but receiving input from the port is a problem. 

Command Line Terminal (CLT) for NT is a simple freeware utility designed to solve this issue. It can:

  • Opens a COM port using parameters you specify in an environment variable
  • Prints a message saying the port is open, or terminates with an error 
  • Sends whatever you type at the console to the COM port 
  • Prints whatever comes back from the COM port on the console 
  • Exits if you hit

Download CLT.ZIP (32KB) from

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