Here's a hard sudoku

Just found this one I used to test a sudoku-solving program about 4 years ago.  There is a singular solution but it took around 2 minutes to find with my algorithms.

9 4 1 5 2 8 3 5 7 1 9 2 2 4 3 8 7 6 4 1 9

Feel free to give it a go.

ipv6 ready