UDP广播协议

    // 设置加入组
    private void chkbxJoinGtoup_Click(object sender, EventArgs e)
    {
        if (chkbxJoinGtoup.Checked == true)
        {
            tbxGroupIp.Enabled = false;
        }
        else
        {
            tbxGroupIp.Enabled = true;
            tbxGroupIp.Focus();
        }
    }

    // 选择发送模式后设置
    private void chkbxBroadcast_Click(object sender, EventArgs e)
    {
        if (chkbxBroadcast.Checked == true)
        {
            tbxSendToGroupIp.Enabled = false;
        }
        else
        {
            tbxSendToGroupIp.Enabled = true;
            tbxSendToGroupIp.Focus();
        }
    }

    // 发送消息
    private void btnSend_Click(object sender, EventArgs e)
    {
        if (tbxMessageSend.Text == "")
        {
            MessageBox.Show("消息内容不能为空！","提示");
            return;
        }

        // 根据选择的模式发送信息
        if (chkbxBroadcast.Checked == true)
        {
            // 广播模式(自动获得子网中的IP广播地址)
            broadcastIpEndPoint = new IPEndPoint(IPAddress.Broadcast, 8002);
        }
        else
        {
            // 组播模式
            broadcastIpEndPoint = new IPEndPoint(IPAddress.Parse(tbxSendToGroupIp.Text), 8002);
        }

        // 启动发送线程发送消息
        Thread sendThread = new Thread(SendMessage);
        sendThread.Start(tbxMessageSend.Text);
    }

    // 发送消息
    private void SendMessage(object obj)
    {
        string message = obj.ToString();
        byte[] messagebytes = Encoding.Unicode.GetBytes(message);
        sendUdpClient = new UdpClient();
        // 发送消息到组播或广播地址            sendUdpClient.Send(messagebytes, messagebytes.Length, broadcastIpEndPoint);
        sendUdpClient.Close();
        
        // 清空编辑消息框            ResetMessageText(tbxMessageSend);
    }

    // 利用委托回调机制来实现界面上的消息清空操作
    delegate void ResetMessageTextCallBack(TextBox textbox);
    private void ResetMessageText(TextBox textbox)
    {
        if (textbox.InvokeRequired)
        {
            ResetMessageTextCallBack resetMessageCallback = ResetMessageText;
            textbox.Invoke(resetMessageCallback, new object[] { textbox });
        }
        else
        {
            textbox.Clear();
            textbox.Focus();
        }
    }

    // 接收消息
    private void btnReceive_Click(object sender, EventArgs e)
    {
        chkbxJoinGtoup.Enabled = false;
        // 创建接收套接字
        IPAddress localIp = IPAddress.Parse(tbxlocalip.Text);
        IPEndPoint localIpEndPoint = new IPEndPoint(localIp, int.Parse(tbxlocalport.Text));
        receiveUdpClient = new UdpClient(localIpEndPoint);
        // 加入组播组
        if (chkbxJoinGtoup.Checked == true)
        {
            receiveUdpClient.JoinMulticastGroup(IPAddress.Parse(tbxGroupIp.Text));
            receiveUdpClient.Ttl = 50;
        }

        // 启动接受线程
        Thread threadReceive = new Thread(ReceiveMessage);
        threadReceive.Start();
    }

    // 接受消息方法
    private void ReceiveMessage()
    {
        IPEndPoint remoteIpEndPoint = new IPEndPoint(IPAddress.Any, 0);
        while (true)
        {
            try
            {
                // 关闭receiveUdpClient时此时会产生异常
                byte[] receiveBytes = receiveUdpClient.Receive(ref remoteIpEndPoint);
                string receivemessage = Encoding.Unicode.GetString(receiveBytes);

                // 显示消息内容
                ShowMessage(lstMessageBox, string.Format("{0}[{1}]", remoteIpEndPoint, receivemessage));
            }
            catch
            {
                break;
            }
        }
    }
    // 通过委托回调机制显示消息内容
    delegate void ShowMessageCallBack(ListBox listbox,string text);
    private void ShowMessage(ListBox listbox, string text)
    {
        if (listbox.InvokeRequired)
        {
            ShowMessageCallBack showmessageCallback = ShowMessage;
            listbox.Invoke(showmessageCallback, new object[] { listbox, text });
        }
        else
        {
            listbox.Items.Add(text);
            listbox.SelectedIndex = listbox.Items.Count - 1;
            listbox.ClearSelected();
        }
    }

    // 清空消息列表
    private void btnClear_Click(object sender, EventArgs e)
    {
        lstMessageBox.Items.Clear();
    }

    // 停止接收
    private void btnStop_Click(object sender, EventArgs e)
    {
        chkbxJoinGtoup.Enabled =true;
        receiveUdpClient.Close();
    }

   
}