Remarks

Channel Positive numeric constant that refers to the opened channel.
Var A variable that receives the value from the software UART.
Note that the channel must be opened with the OPEN statement.
Also, note that the CLOSE statement, must be the last in your program. Please see comment on OPEN statement
An optional TIMEOUT can be specified so that the routine will return when no character is received.

See also
PUT $TIMEOUT

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

Printbin #1, a 'Printbin is also supported
Inputbin #2, a 'Inputbin is also supported

Close #1 ' finally close device
Close #2
End

To use the TIMEOUT option include :
$TIMEOUT
Get #2 , A TIMEOUT = 10000 'get character from comport