Check if custom registration form is submitted, then open SOAP/DB connection

I would like to open a SOAP connection that reflects changes to another database onlywhen the following forms has been submitted(Register & Update profile forms) through WordPress. I am able to get the connection working using a try/catch block statement but it seems like the connection are always present so it's slowing the site down alot and it's not safe.

Does anyone know how to check when an user submits a form?

All I could think of is using this code: if($_SERVER['REQUEST_METHOD'] == "POST")

and doing something like this:

if($_SERVER['REQUEST_METHOD'] == "POST"){
try{
//import soap class
// connect to another DB
// Do more stuff here... }
catch(exception $e){
// errror }
}