How to set up for raw I/O (code examples needed)

[jeff marder]

Could someone please show me how to set up a device to do raw I/O
using termio and / or ioctl calling sequences?

The data I want to read/write is sent at 9600 baud, no parity, 1-stop.

The data I want to read comes in variable message sizes, from 10 bytes
to approximately 135 bytes.  When I execute a read command, what byte
size should I ask for?????   Note that the data stream is NOT contiguous;
the messages will come in very sporadically.