From Lundman Wiki
Send USER and PASS for authentication. This requires a valid user and password pair already registered on FXP.One. If FXP.One was started with no user database files, it will create one with the account user "admin" and password "admin".
[ Minimal Required Fields] >> USER=<str> - USER name >> PASS=<str> - PASSWORD
[ Optional Arguments ]
[ Returns ] >> OK - Authentication was successful. >> CODE=<int> - Failure code. >> MSG=<str> - Human readable string message.
[ Example ] << AUTH|USER=admin|PASS=admin >> AUTH|OK|MSG=Successful or >> AUTH|CODE=502|MSG=Login incorrect or >> AUTH|CODE=503|MSG=Secure channel enforced.