The need for efficient storing of IP numbers came up in discussion thread. With help of this conversion to/from the 32 bit numbers that IP numbers (the old ones) represent I could push the time of finding unique IP numbers from 10 million random numbers down to under two minutes in my Sempron 1,5 GB RAM ACER computer:
..... 9940000 254.196.90.223 9950000 255.5.230.221 9960000 255.71.96.186 9970000 255.135.189.144 9980000 255.201.68.112 1 min 40.639 s ready, result stored in "unique_ip.txt". Push enter to quit.
Here is the functions for IP number conversion from my routine: