HTTP_POST Intermittent Problem

I'm using the code below and about a third of the posts aren't getting through. We have no idea why and don't know where to start to trouble shoot. Any ideas? Thanks. Jeff function http_post($host, $path, $data) {

     $http_response = '';
     $content_length = strlen($data);

     $fp = fsockopen($host, 80);
     fputs($fp, "POST $path HTTP/1.1\r\n");
     fputs($fp, "Host: $host\r\n");
     fputs($fp, "Content-Type: application/x-www-form-urlencoded\r\n");
     fputs($fp, "Content-Length: $content_length\r\n");
     fputs($fp, "Connection: close\r\n\r\n");
     fputs($fp, $data);
     while (!feof($fp))
     {
          $http_response .= fgets($fp, 128);
     }
     fclose($fp);

     return $http_response;

} $http_response = http_post('www.blah.com', '/test.aspx?', 'data');