let me see if i got you correctly... you want to have a console application that "simulates" a form submit ? (to update your dyndns ip ?
ok, there are several ways you can solve this: URLConnection and its subclass HTTPUrlConnection (huc). the huc class supports some parts of the http protocol but is not very convenient if you want to do more complicate stuff (including redirection and so on). there is a library from apache: jakarta http client which can help you sending form data.