diff --git a/wp-includes/functions.php b/wp-includes/functions.php
index 0fbb6d658d..3ddc0c808d 100644
--- a/wp-includes/functions.php
+++ b/wp-includes/functions.php
@@ -638,17 +638,13 @@ function pingback($content, $post_ID) {
 	// original code by Mort (http://mort.mine.nu:8080)
 	$log = debug_fopen('./pingback.log', 'a');
 	$post_links = array();
-	debug_fwrite($log, 'BEGIN '.time()."\n");
+	debug_fwrite($log, 'BEGIN '.date('YmdHis', time())."\n");
 
 	// Variables
 	$ltrs = '\w';
 	$gunk = '/#~:.?+=&%@!\-';
 	$punc = '.:?\-';
 	$any = $ltrs.$gunk.$punc;
-	$pingback_str_dquote = 'rel="pingback"';
-	$pingback_str_squote = 'rel=\'pingback\'';
-	$x_pingback_str = 'x-pingback: ';
-	$pingback_href_original_pos = 27;
 
 	// Step 1
 	// Parsing the post, external links (if any) are stored in the $post_links array
@@ -679,78 +675,11 @@ function pingback($content, $post_ID) {
 	}
 
 	foreach ($post_links as $pagelinkedto){
-		debug_fwrite($log, 'Processing -- '.$pagelinkedto."\n\n");
 
-		$bits = parse_url($pagelinkedto);
-		if (!isset($bits['host'])) {
-			debug_fwrite($log, 'Couldn\'t find a hostname for '.$pagelinkedto."\n\n");
-			continue;
-		}
-		$host = $bits['host'];
-		$path = isset($bits['path']) ? $bits['path'] : '';
-		if (isset($bits['query'])) {
-			$path .= '?'.$bits['query'];
-		}
-		if (!$path) {
-			$path = '/';
-		}
-		$port = isset($bits['port']) ? $bits['port'] : 80;
+		debug_fwrite($log, "Processing -- $pagelinkedto\n");
+		$pingback_server_url = discover_pingback_server_uri($pagelinkedto, 2048);
 
-		// Try to connect to the server at $host
-		$fp = fsockopen($host, $port, $errno, $errstr, 3);
-		if (!$fp) {
-			debug_fwrite($log, 'Couldn\'t open a connection to '.$host."\n\n");
-			continue;
-		}
-
-		// Send the GET request
-		$request = "GET $path HTTP/1.1\r\nHost: $host\r\nUser-Agent: WordPress/$wp_version PHP/" . phpversion() . "\r\n\r\n";
-		ob_end_flush();
-		fputs($fp, $request);
-
-		// Start receiving headers and content
-		$contents = '';
-		$headers = '';
-		$gettingHeaders = true;
-		$found_pingback_server = 0;
-		while (!feof($fp)) {
-			$line = fgets($fp, 4096);
-			if (trim($line) == '') {
-				$gettingHeaders = false;
-			}
-			if (!$gettingHeaders) {
-				$contents .= trim($line)."\n";
-				$pingback_link_offset_dquote = strpos($contents, $pingback_str_dquote);
-				$pingback_link_offset_squote = strpos($contents, $pingback_str_squote);
-			} else {
-				$headers .= trim($line)."\n";
-				$x_pingback_header_offset = strpos(strtolower($headers), $x_pingback_str);
-			}
-			if ($x_pingback_header_offset) {
-				preg_match('#x-pingback: (.+)#is', $headers, $matches);
-				$pingback_server_url = trim($matches[1]);
-				debug_fwrite($log, "Pingback server found from X-Pingback header @ $pingback_server_url\n");
-				$found_pingback_server = 1;
-				break;
-			}
-			if ($pingback_link_offset_dquote || $pingback_link_offset_squote) {
-				$quote = ($pingback_link_offset_dquote) ? '"' : '\'';
-				$pingback_link_offset = ($quote=='"') ? $pingback_link_offset_dquote : $pingback_link_offset_squote;
-				$pingback_href_pos = @strpos($contents, 'href=', $pingback_link_offset);
-				$pingback_href_start = $pingback_href_pos+6;
-				$pingback_href_end = @strpos($contents, $quote, $pingback_href_start);
-				$pingback_server_url_len = $pingback_href_end-$pingback_href_start;
-				$pingback_server_url = substr($contents, $pingback_href_start, $pingback_server_url_len);
-				debug_fwrite($log, "Pingback server found from Pingback <link /> tag @ $pingback_server_url\n");
-				$found_pingback_server = 1;
-				break;
-			}
-		}
-
-		if (!$found_pingback_server) {
-			debug_fwrite($log, "Pingback server not found\n\n*************************\n\n");
-			@fclose($fp);
-		} else {
+		if($pingback_server_url) {
 
 			 // Now, the RPC call
 			$method = 'pingback.ping';
@@ -778,6 +707,96 @@ function pingback($content, $post_ID) {
 	debug_fclose($log);
 }
 
+function discover_pingback_server_uri($url, $timeout_bytes = 2048) {
+
+	$byte_count = 0;
+	$contents = '';
+	$headers = '';
+	$pingback_str_dquote = 'rel="pingback"';
+	$pingback_str_squote = 'rel=\'pingback\'';
+	$x_pingback_str = 'x-pingback: ';
+	$pingback_href_original_pos = 27;
+
+	extract(parse_url($url));
+
+	if (!isset($host)) {
+		// Not an URL. This should never happen.
+		return false;
+	}
+
+	$path  = (!isset($path)) ? '/'        : $path;
+	$path .= (isset($query)) ? '?'.$query : '';
+	$port  = (isset($port))  ? $port      : 80;
+
+	// Try to connect to the server at $host
+	$fp = fsockopen($host, $port, $errno, $errstr, 3);
+	if (!$fp) {
+		// Couldn't open a connection to $host;
+		return false;
+	}
+
+	// Send the GET request
+	$request = "GET $path HTTP/1.1\r\nHost: $host\r\nUser-Agent: WordPress/$wp_version PHP/" . phpversion() . "\r\n\r\n";
+	ob_end_flush();
+	fputs($fp, $request);
+
+	// Let's check for an X-Pingback header first
+	while (!feof($fp)) {
+		$line = fgets($fp, 512);
+		if (trim($line) == '') {
+			break;
+		}
+		$headers .= trim($line)."\n";
+		$x_pingback_header_offset = strpos(strtolower($headers), $x_pingback_str);
+		if ($x_pingback_header_offset) {
+			// We got it!
+			preg_match('#x-pingback: (.+)#is', $headers, $matches);
+			$pingback_server_url = trim($matches[1]);
+			return $pingback_server_url;
+		}
+		if(strpos(strtolower($headers), 'content-type: ')) {
+			preg_match('#content-type: (.+)#is', $headers, $matches);
+			$content_type = trim($matches[1]);
+		}
+	}
+
+	if (preg_match('#(image|audio|video|model)/#is', $content_type)) {
+		// Not an (x)html, sgml, or xml page, no use going further
+		return false;
+	}
+
+	while (!feof($fp)) {
+		$line = fgets($fp, 1024);
+		$contents .= trim($line);
+		$pingback_link_offset_dquote = strpos($contents, $pingback_str_dquote);
+		$pingback_link_offset_squote = strpos($contents, $pingback_str_squote);
+		if ($pingback_link_offset_dquote || $pingback_link_offset_squote) {
+			$quote = ($pingback_link_offset_dquote) ? '"' : '\'';
+			$pingback_link_offset = ($quote=='"') ? $pingback_link_offset_dquote : $pingback_link_offset_squote;
+			$pingback_href_pos = @strpos($contents, 'href=', $pingback_link_offset);
+			$pingback_href_start = $pingback_href_pos+6;
+			$pingback_href_end = @strpos($contents, $quote, $pingback_href_start);
+			$pingback_server_url_len = $pingback_href_end - $pingback_href_start;
+			$pingback_server_url = substr($contents, $pingback_href_start, $pingback_server_url_len);
+			// We may find rel="pingback" but an incomplete pingback URI
+			if ($pingback_server_url_len > 0) {
+				// We got it!
+				return $pingback_server_url;
+			}
+		}
+		$byte_count += strlen($line);
+		if ($byte_count > $timeout_bytes) {
+			// It's no use going further, there probably isn't any pingback
+			// server to find in this file. (Prevents loading large files.)
+			return false;
+		}
+	}
+
+	// We didn't find anything.
+	return false;
+}
+
+
 /* wp_set_comment_status:
    part of otaku42's comment moderation hack
    changes the status of a comment according to $comment_status.