Re: physical layer

You really can't do anything with the physical layer in Java's native code. Java is so far removed from the physical layer that your question really doesn't make much sense.
To work with the physical layer, you'll need to either write some C code and call it from the Java code or even write some assembly code and reference that from the C code.
What exactly are you trying to do? Maybe there is a better way to get at it.

Here is a relative link that may be usefull: http://www.koders.com/java/fid4B98C09E6A335C71BEBC5ACE5DF6BE974C35438B.aspx?s=idef%3Afile

That is an example of a link layer (which is a step above the physical layer). The link layer is still rather dependent on the hardware, so the code there won't translate well to other platforms.

"The physical layer provides a bit stream interface to the link layer. This layer is very hardware-dependent."

This is why you can't write general physical layer code. It would have to specifically target the exact hardware you are using. You would need entirely different code even on the same machine if you plugged it into a different network. Also, the code would very from machine to machine even running the same OS.

Good answer to the question