When the port is open you must call ReadFile & WriteFile for read and write data the in COM port.

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Declare Long ReadFile in "kernel32" Long hFile , STRING @lpBuffer, Long nNumberOfBytesToRead, Long @lpNumberOfBytesRead, long lpOverlapped

LOCAL hPort,lpNumberOfBytesRead, lpBuffer
lpNumberOfBytesRead = 50
lpBuffer = SPACE(50)
hPort = CreateFile (lcPort, GENERIC_READ, 0,0,;
OPEN_EXISTING, FILE_FLAG_OVERLAPPED, 0)

ReadFile( hPort, @lpBuffer, 50, @lpNumberOfBytesRead, 0 )

IDEM for WriteFile function.