Hello Inma,
I'm no digital expert, but I believe you want pattern I/O. True handshaking (one example) is where your instrument tells your program it has a data value to be read. Your program reads it and lets your instrument know it has been read. Until then your instrument will wait to send the next value. The idea is each side waits for a signal from the other side before continuing. This communication takes place over handshaking lines.
With pattern I/O, you set up a digital input or output to be clocked in or out at a specified rate. In this case you expect the other end to keep up with your rate. If the other end doesn't keep up, you may read "bad" data, or write data that gets skipped by the other side.
I hope this helps,
Doug Norman