Limitation of SOAP Connections

Hi,

I'm using a PHP Script to create Courses and add/remove Users to Moodle 2.4 trough the SOAP Webservice.

It works great for a small amount of Courses, but breaks if there are too many Courses. The Script sends hundrets of Soap Calls.

After a while the script breaks with the message:
PHP Fatal error: Uncaught SoapFault exception: [HTTP] Could not connect to host in ...

There is no problem if i split the script into pieces (not more than 50 Courses at once) so the Host URL is correct an Soap functions work correctly.

Are there any limitation? For examle: Not more than 500 Soap Requests per Hour - or something else?The PHP Script is running on CLI with no memory Limit

Thanks for your help.