The msMouseCommPort member in the MOUSEINFO structure, new for Windows 3.1, specifies which communications port Windows is using to reserve for the mouse. The mouse driver must set this member to one of the following values when processing the Enable function.
| Value | Meaning |
| 0 | No port used. |
| 1 | Communications port 1 (COM1). |
| 2 | Communications port 2 (COM2). |
| 3 | Communications port 3 (COM3). |
| 4 | Communications port 4 (COM4). |