线程间操作无效: 从不是创建控件“label4”的线程访问它。

//主线程
 public delegate void UpdateMessage(string mes);
 public void UpdatePortMessage(string mes)
        {
            this.txtMessage.AppendText(string.Format("Connected {0}. succeed", mes) + "\r\n");
            this.txtClientIP.Text = mes;
        }

// 线程1
  UpdateMessage upPort = new UpdateMessage(UpdatePortMessage);
                        this.BeginInvoke(upPort, point);

http://bbs.csdn.net/topics/390535667