The URL where the user (browser) returns after authenticating.
int SetReturnURL(QString qsReturnURL);
When ClientProfile is set to cfApplication this will be automatically set to the address of the local embedded web server. In that case this property can be inspected to determine the URL where the user will be redirected, but does not need to be set.
When calling GetAuthorizationURL, which is common when ClientProfile is set to cfWebBrowser, set this property to the URL on your server where the user will be redirected after authenticating with the authorization server.