diff --git a/trunk/research/api-server/static-dir/index.html b/trunk/research/api-server/static-dir/index.html
index 6c8f0f0e9..d54b70289 100755
--- a/trunk/research/api-server/static-dir/index.html
+++ b/trunk/research/api-server/static-dir/index.html
@@ -62,8 +62,9 @@
         // The player url.
         if (true) {
             const prefix = `players/?schema=${window.location.protocol.replace(':', '')}`;
+            const httpPort = window.location.port || (window.location.protocol === 'http:' ? 80 : 443);
             // If not 8080, user should proxy to the default port.
-            const query = parseInt(window.location.port) === 8080 ? '' : `&port=${window.location.port}`;
+            const query = parseInt(window.location.port) === 8080 ? '' : `&port=${httpPort}`;
             document.getElementById("enPlayer").setAttribute('href', `${prefix}${query}`);
             document.getElementById("cnPlayer").setAttribute('href', `${prefix}${query}`);
         }