ems.diff

diff --git a/src/library_sockfs.js b/src/library_sockfs.js
index 86f8605..a512b4d 100644
--- a/src/library_sockfs.js
+++ b/src/library_sockfs.js
@@ -180,6 +180,9 @@ mergeInto(LibraryManager.library, {
               if ('string' === typeof Module['websocket']['url']) {
                 url = Module['websocket']['url']; // Fetch runtime WebSocket URL config.
               }
+              if ('function' === typeof Module['websocket']['url']) {
+                url = Module['websocket']['url'](addr, port); // Fetch runtime WebSocket URL config.
+              }
             }
 
             if (url === 'ws://' || url === 'wss://') { // Is the supplied URL config just a prefix, if so complete it.