[C# 网络编程系列]专题七：UDP编程补充—

[C# 网络编程系列]专题七：UDP编程补充——UDP广播程序的实现

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();}}
}

广播演示结果（接收端直接点接收按钮后开启接受线程，在发送端勾选“广播选项”输入发送信息点发送按钮后的界面如下）：