Serial Hardware Handshaking in Windows XP SP3 Broken?

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9600 8N1 Transmit only, both DSR and CTS asserted by device (printer). Behavior is apparently no different than handshake none. Works fine with windows-specific code which sets the DCB as follows:

dcb.fOutxCtsFlow = true;  // Enable CTS monitoring
dcb.fOutxDsrFlow = true;  // Enable DSR monitoring
dcb.fDtrControl = DTR_CONTROL_HANDSHAKE;  // Enable DTR handshaking
dcb.fOutX = false;  // Disable XON/XOFF for transmission
dcb.fInX = false;  // Disable XON/XOFF for receiving
dcb.fRtsControl = RTS_CONTROL_HANDSHAKE;  // Enable RTS handshaking

Couldn't find where the DCB is set in asio...