Login with curl

Hello gleamtech team

We need to do an automated export of files from FileVista. To realize that I tried to implement a login via Curl in php.
After the login I get the following returned:
<?xml version="1.0" encoding="utf-8"?>
<Login error="0" loginOk="1" message="" />

After that I tried to acccess the root or /filevistacontrol/filevista.asmx/GetList. I always ended up with 
<?xml version="1.0" encoding="utf-8"?>
<Result error="0" message="Session is expired" command="RefreshPage" />

When I don't use the cookie I generate with CuRL, but I use pass one in the curl request to /filevistacontrol/filevista.asmx/GetList (with which I logged in previously), it all works fine.
The cookie which is set by CuRL is correct, the timeout is set to 0 for the session_Id.

Question: what else do I need to do after the login to use my session? Why does it say it's expired? 

Thanks
Markus