[Modify] Throw exception

websocket-sharp/Server/WebSocketSessionManager.cs

@@ -566,10 +566,9 @@ namespace WebSocketSharp.Server
     /// </returns>
     public Dictionary<string, bool> Broadping ()
     {
-      var msg = _state.CheckIfAvailable (false, true, false);
+      if (_state != ServerState.Start) {
-      if (msg != null) {
+        var msg = "The current state of the manager is not Start.";
-        _logger.Error (msg);
+        throw new InvalidOperationException (msg);
-        return null;
       }
 
       return Broadping (WebSocketFrame.EmptyPingBytes, _waitTime);