Handshaking
An integral part of managing the receive and transmit buffers is ensuring that
the back-and-forth transmission of data is successful — that the speed at which
the data is being received does not overflow the buffer limits, for example.
Handshaking refers to the internal communications protocol by which data is
transferred from the hardware port to the receive buffer. When a character of
data arrives at the serial port, the communications device has to move it into
the receive buffer so that your program can read it. A handshaking protocol
ensures that data is not lost due to a buffer overrun, where data arrives at
the port too quickly for the communications device to move the data into the
receive buffer.
You set the Handshaking property to specify the handshaking protocol to be
used by your application. By default, this value is set to none (comNone). You
can, however, specify one of the other following protocols:
|
Setting
|
Value
|
Description
|
| comNone |
0 |
No handshaking (Default). |
| comXOnXOff |
1 |
XOn/XOff handshaking. |
| comRTS |
2 |
RTS/CTS (Request To Send/Clear To Send) handshaking. |
| comRTSXOnXOff |
3 |
Both Request To Send and XOn/XOff handshaking. |
The protocol that you choose depends upon the device to which you’re connecting.
Setting this value to comRTSXOnXOff supports both of the protocols.
In many cases, the communications protocol itself handles handshaking. Therefore,
setting this property to something other than comNone may result in conflicts.
Note If you do set this value to either comRTS or
comRTSXOnXOff, you need to set the RTSEnabled property to True. Otherwise, you
will be able to connect and send, but not receive, data.