Revise port matching logic

index.bs

@@ -4035,21 +4035,27 @@ this algorithm returns normally if compilation is allowed, and throws a
   and [=url/scheme=]. For example, "80" <a>`port-part` matches</a> matches "80"/"http".
 
   <ol class="algorithm">
-    1.  If |port A| is the empty string:
+    1.  Let |adjusted port A| be the result of removing any leading "0"s from |port A|.
 
-        1.  If |port B| is the <a>default port</a> for |scheme B|, return "`Matches`". Otherwise,
-            return "`Does Not Match`".
+    2.  If |adjusted port A| is <a for="string" lt="is">identical to</a> |port B|, return "`Matches`".
 
-    2.  If |port A| is equal to "*", return "`Matches`".
+    3.  If |port A| is equal to "*", return "`Matches`".
 
-    3.  If |port A| is <a for="string" lt="is">identical to</a> |port B|, return "`Matches`".
+    4.  If |port A| is the empty string:
 
-    4.  If |port B| is the empty string:
+        1.  Let |default port b| be the <a>ASCII string</a> of the <a>default port</a> for |scheme B|
+            if it is not null, otherwise the empty string.
 
-        1.  If |port A| is the <a>default port</a> for |scheme B|, return "`Matches`". Otherwise,
-            return "`Does not Match`".
+        2.  If |port B| is <a for="string" lt="is">identical to</a> |default port B|, return "`Matches`".
 
-    5. Return "`Does Not Match`".
+    5.  If |port B| is the empty string:
+
+        1.  Let |default port b| be the <a>ASCII string</a> of the <a>default port</a> for |scheme B|
+            if it exists and is not null, otherwise the empty string.
+
+        2.  If |adjusted port A| is <a for="string" lt="is">identical to</a> |default port B|, return "`Matches`".
+
+    6. Return "`Does Not Match`".
   </ol>
 
   <h5 id="match-paths" algorithm>