Could not open socket in PHP form

I have a user registration form. I test it in my local sever and it worked fine. But when I tested it in my remote server, the error message "Could not open socket" is shown after submitting the form.
After google, I found the following article quite helpful:
http://ezinearticles.com/?Could-Not-Open-Socket-reCAPTCHA-Error&id=5882695

The reason is due to  recaptcha. In recaptchalib.php
line 40 change
define("RECAPTCHA_VERIFY_SERVER", "www.google.com");
to
define("RECAPTCHA_VERIFY_SERVER", "74.125.227.48");

i.e changing www.google.com to 74.125.227.48 solved the problem.