Try pinging and/or telnet'ing from that other pc to yours and see if the pc can actually see you. If it can't, could be that a firewall or other network security measure is blocking it for some reason.
Ah ok, sorry I misunderstood what you were trying to do.
The SUBSTR() function might be able to help.
SELECT TARIFF FROM RATES WHERE COUNTRYCODE = SUBSTR(<phonenumber>, 0, 3)
You probably have to fiddle with it, but basically this will return the tariffs for all countrycodes that match the first three digits of the phone number. Again, this is assuming that the length of the country code is 3. You may need an if-statement and select country codes of length 2 if no match is made on the first three and finally the first digit only if no match is found there.
You will need a pretty good understanding of how to use I/O in java to do this assignment. Take a look at the java API in the java.io package and I'm sure there are some tutorials on the sun website about I/O. The rest of the program is just a series of if-else statements.
Have a try and if you are still having problems post some of your code for us to have a look at. We can then try to steer you in the right direction. :)
