#4104 get_default_port is an instance method in v5.x

xpra/gtk_common/start_gui.py

@@ -673,7 +673,7 @@ def get_run_command(self, attach=False):
                 port = int(self.port_entry.get_text())
             except ValueError:
                 port = 0
-            if port and port!=get_default_port(mode):
+            if port and port!=self.get_default_port(mode):
                 uri += ":%s" % port
             uri += "/"
             if display: