private void btnSend_Click(object sender, EventArgs e)
        {
            if (!_isRunning)
            {
                MessageBox.Show("请先连接");
                return;
            }
            if (string.IsNullOrEmpty(txtDestClient.Text))
            {
                MessageBox.Show("请填写发送目标");
                return;
            }
            if (string.IsNullOrEmpty(txtMessage.Text))
            {
                MessageBox.Show("请填写消息");
                return;
            }
            var message = new Proxy.MessageEntity
            {
                Receiver    = txtDestClient.Text,
                MessageType = MessageTypes.Default,
                Content     = txtMessage.Text,
            };

            _client.SendMessage(message);
            txtReceivedMessage.Text += string.Format("给 {0} 发送消息 {1},\r\n", txtDestClient.Text, txtMessage.Text);
        }