@Override
    public void closeStandaloneConnection(Connection conn) {
        ensureStarted();
        if (null != conn) {
            conn.close();
        }
    }
Shutdown.
<p>
Notice:<br>
  <li>Rpc client can not be used any more after shutdown.
  <li>If you need, you should destroy it, and instantiate another one.
src/main/java/com/alipay/remoting/rpc/RpcClient.java