to debug your external connection problem, you can use mtrace($string) in the php code to trace the error. what mtrace does is shows the output on the screen when running the php script from the cli. it also has the option to add seconds to it, that will hold the message on the string for that long.
For eg;
mtrace("This is where i am right now",50); will hold the msg for 50 seconds
For more usages of mtrace, refer the file lib.php in the database folder under enrol.
Hope this is clear.
Hittesh