C#网络编程系列七：UDP编程补充-c#网络编程

上次因为时间的关系，所以把上一个专题遗留下的一个问题在本专题中和大家分享下，本专题主要介绍下如何实现UDP广播的程序，下面就直接介绍实现过程和代码以及运行的结果。

一、程序实现

UDP广播程序的实现代码：

using System;  
using System.Net;  
using System.Net.Sockets;  
using System.Text;  
using System.Threading;  
using System.Windows.Forms;  
namespace UDPBroadcast  
{  
    /// <summary>  
    /// 在界面上，用户可以设置本地进程的IP地址和端口号，并将地址加入某个组播组；  
    /// 可以输入发送消息的目的组的地址，并且勾选“广播”复选框将采用广播的方式发送信息  
    /// 在界面上点击“接受按钮”就启动接收线程，这样程序就可以接收广播或组播的信息  
    /// </summary>  
    public partial class UdpBroadcasefrm : Form  
    {  
        private UdpClient sendUdpClient;  
        private UdpClient receiveUdpClient;  
        // 组播IP地址  
        IPEndPoint broadcastIpEndPoint;  
        public UdpBroadcasefrm()  
        {  
            InitializeComponent();  
            IPAddress[] ips = Dns.GetHostAddresses(Dns.GetHostName());  
            tbxlocalip.Text = ips[5].ToString();  
            tbxlocalport.Text = "8002";  
            // 默认组,组播地址是有范围  
            // 具体关于组播和广播的介绍参照我上一篇博客UDP编程  
            // 本地组播组  
            tbxGroupIp.Text = "224.0.0.1";  
            // 发送到的组播组  
            tbxSendToGroupIp.Text = "224.0.0.1";  
        }  
 
        // 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();  
        }    
    }  
}