You generally only need such programs on 'doze due the ( you guessed it) fact that you are not granted knowledge of how windows works. Your post implies you are operating on something other than Windows. If this is the case, then you can just get in the middle between the program and the port.

Under any Unix or BSD (and this should include OSX), just rename your serial port file and create a named pipe in it's place. Then create a small perl script to sit in between the two files, reading from one and writing to the other, and vice versa.

Also, programs like ttysnoop are capable of getting in the middle like this.

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Jeremy
I didn't believe in evil until I dated it.