With the release of Indigo Terminal Emulator Version 3, Indigo now natively supports com ports addressed up to port 256.
If you have purchased Indigo Version 2, you can upgrade to Version 3 at no additional cost.
Please see the following topic for more information on upgrading to Version 3 from Version 2
>> Upgrade from Indigo Version 2 to Version 3
Indigo facilitates serial communication through a Microsoft Serial Communication library that limits com ports to port 16 and below. If possible, reassign your serial port to com port 16 or below.
Here is a help document on how to change the COM port settings:
Change Com Port Assignment in Windows
If you cannot change the port number for your serial device, then there is an alternate solution. You will need to replace the Microsoft Serial Communication library with a modified version that enables ports above 16. Please download the following ZIP file and read the instructions for more information.
Alternate Serial Communications Library
Indigo Version 3 BETA supports com ports up to port 256.