Hi here's another UDF for the serial port. It is very similar to CommAPI using kernel32.dll, but all code is packed into a single file without any dependencies, not even using WinAPI.au3. It differs from existing UDF that it doesn't allow a timeout when reading, instead it always returns immediately, either with the requested amount ob bytes read or with a failure status. And of course there is a function provided to query the amount of available bytes in the receive buffer. The reason behi