Remarks

channel Positive numeric constant that refers to the opened channel.
var A variable or constant who's value is sent to the software UART.
See also
GET

Example

Open "com3.1:9600" For Output As #1 'p3.1 is normally used for tx so testing is easy
Open "com3.0:9600" For Input As #2 'p3.0 is normally used for RX so testing is easy

S = "test this" 'assign string
Dum = Len(s) 'get length of string
For I = 1 To Dum 'for all characters from left to right

A = Mid(s , I , 1) 'get character
Put #1 , A 'write it to comport
Next

Do
Get #2 , A 'get character from comport
Put #1 , A 'write it back
Print A 'use normal channel
Loop

Close #1 ' finally close device
Close #2
End