MySqlConnection myConn = new MySqlConnection("server=192.168.1.103;database=productcatalog;uid=root;password=12345678");
// where 192.168.1.103 is the PC's IP address.
above code does not give me any problem.

but when I have this:
MySqlConnection myConn = new MySqlConnection("server=localhost;database=productcatalog;uid=root;password=12345678");
it gives error: Unable to connect to any of the specified MySQL hosts.
I have thought that both the above statements are equivalent, are they not?

even when I uninstall MySQL and re-install again on this particular PC, it gives the same error.

However, when I test the above 2 statements with another PC, it does not give any error of such. I am puzzed what are the causes of the problem on that particular PC. Any hint? thanks.