SMFHacks.com

Action Required before October 7, 2013
Merchants need to update their scripts IPN and PDT to use HTTP 1.1 and include the HTTP header "Host" and "Connection: close" in the script IPN ​​return shipping.

Example with Host as www.paypal.com (make the necessary changes if you are using ipnpb.paypal.com):

ASP
//Establezca los valores para la solicitud de regreso
req.Method="POST";
req.Host="'www.paypal.com'";
req.ContentType="application/x-www-form-urlencoded";

Perl
$req=HTTP::Request->new('POST', 'https://www.paypal.com/cgi-bin/webscr');
$req->content_type('application/x-www-form-urlencoded');
$req->header(Host=> 'www.paypal.com');
$req->header(Connection=> 'close');
PHP
// envío de regreso al sistema PayPal para que lo valide
$header="POST /cgi-bin/webscr HTTP/1.1\r\n";
$header .="Content-Type: application/x-www-form-urlencoded\r\n";
$header .="Host: www.paypal.com\r\n";
$header .="Connection: close\r\n\r\n";

Java
HttpsURLConnection  uc=(HttpsURLConnection) u.openConnection();
uc.setDoOutput(true);
uc.setRequestProperty("Content-Type","application/x-www-form-urlencoded");
uc.setRequestProperty("Host", "www.paypal.com");
uc.setRequestProperty("Connection", "Close");

The Sandbox environment is configured to reject HTTP requests that do not have the header "Host" HTTP 400 error with. Businesses can use the PayPal Sandbox environment to certify the changes made to your scripts IPN and PDT.

For more information about PDT and IPN, see http://www.paypal.com/pdt and http://www.paypal.com/ipn. For additional information or have any questions about this change, please contact the Technical Support team to trade through https://www.paypal.com/mts PayPal.

Sincerely,

PayPal