Comments by Chad3F (Top 6 by date)

If you have any control over the receiving side, then it should be change to use the raw digest bytes (typically encoded as hex) rather than a bigint. This is normally how they are represented in text by almost everything. Another comment already mentioned this, but it should be emphasized.

In this example, it would be: eccfac173ba2b3438e9542455aa4d3065e3f11c51df755bab51d15f067745d12

Can you give an example input and your desired output (or better yet, two different examples). I'm still unsure what you want, based on your comment response.

Are you able to control the fax machine using normal standalone serial port applications? I just want to verify you aren't trying to learn how to communicate with the fax AND learning how to use COM ports in java at the same time (with potential problems being one, the other, or both).

You may want to use htmlspecialchars() in instead of rolling your own parseToXML() function.