You need to get the page you're logging into.

GET /login.php?u=nick&p=pass HTTP/1.1 for example.

Or just GET /login.php HTTP/1.1


Password data are usually sent with POST.

var %data = user=stefys&pass=mysecretpass
sockwrite -n $sockname POST /login.php HTTP/1.1
sockwrite -n $sockname Host: www.forum.com
sockwrite -n $sockname Content-Length: $len(%data)
sockwrite -n $sockname $crlf
sockwrite -n $sockname %data

But that won't work anyway.. since it's redirecting you to a page that sets cookies, and you won't have them set, since you don't have a real browser. You can read the Cookie: that server sent and set it in a variable. And next time you go to forum, use that cookie shocked