[C#] 建立UDP连接、发送广播

说明：

　　通过建立本地UdpClient与远程UdpClient进行通讯，亦可直接发送到其他已存在的远程端。

　　基本原理：构建一个本地的udpcSend实例，开启多线程进行监听，然后再发送广播。

　　案例有字节数组与十六进制字符串相互转换的方法。

一、案例源码

　　窗体的主要代码：FrmMain.cs

 using System;
 using System.Collections.Generic;
 using System.ComponentModel;
 using System.Data;
 using System.Drawing;
 using System.Linq;
 using System.Net;
 using System.Net.Sockets;
 using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
 using System.Windows.Forms;

 namespace NetworkService
 {
     public partial class FrmMain : Form
     {
         public FrmMain()
         {
             InitializeComponent();

             //string msg = "FF FB 0F";
             //byte[] bytes = Encoding.Default.GetBytes(msg);

             //string res = "";
             //for (int i = 0; i < bytes.Length; i++)
             //{
             //    res += bytes[i].ToString();
             //}
             //MessageBox.Show(res);

         }

         //本地收发UDPClient实例
         private UdpClient udpcSend;
         private UdpClient udpcRecv;
         private bool isLocalConneted = false;//本地是否已连接
         private Thread thrRecv;//本地监听接收线程

         /// <summary>
         /// 【构建本地连接】
         ///  20181021
         /// </summary>
         /// <param name="sender"></param>
         /// <param name="e"></param>
         private void btnConnect_Click(object sender, EventArgs e)
         {
             if (cbProtocol.SelectedIndex != )
             {
                 MessageBox.Show("请暂时选择UDP协议！", "系统提示");
                 return;
             }

             if (string.IsNullOrWhiteSpace(tbLocalIP.Text) || string.IsNullOrWhiteSpace(tbLocalPort.Text))
             {
                 MessageBox.Show("请填写本地IP和端口", "系统提示");
                 return;
             }

             if (!isLocalConneted)//构建本地连接
             {
                 IPEndPoint localIpep = new IPEndPoint(IPAddress.Parse(tbLocalIP.Text), Convert.ToInt32(tbLocalPort.Text));
                 udpcSend = new UdpClient(localIpep);

                 btnConnect.Text = "断开";
                 isLocalConneted = true;

                 //启动监听接收信息
                 BeginListenRecv();
             }
             else//断开本地连接
             {
                 //关闭监听线程
                 thrRecv.Abort();
                 udpcRecv.Close();

                 udpcSend.Close();
                 btnConnect.Text = "连接";
                 isLocalConneted = false;

                 ShowMessage(tbRecvMsg, "[OS]:UDP监听已成功关闭");
             }
         }

         /// <summary>
         /// 【开始监听】
         ///  20181021
         /// </summary>
         private void BeginListenRecv()
         {
             udpcRecv = udpcSend;//接收与发送使用同一个实例

             thrRecv = new Thread(ReceiveMessage);
             thrRecv.Start();

             ShowMessage(tbRecvMsg, "[OS]:Local UDP 监听已成功启动");

         }

         /// <summary>
         /// 【接收信息】
         ///  20181021
         /// </summary>
         private void ReceiveMessage()
         {
             IPEndPoint remoteIpep = new IPEndPoint(IPAddress.Any, );//接收任何来源的信息
             while (true)
             {
                 byte[] byteRecv = udpcRecv.Receive(ref remoteIpep);
                 string message = ByteArrayToHexStringNoBlank(byteRecv);

                 //remoteIpep.Address.ToString() 获取发送源的IP
                 ShowMessage(tbRecvMsg, "[Local Recv]:" + remoteIpep.Address + ":" + remoteIpep.Port + "=" + message);

             }

         }

         /// <summary>
         /// 【发送消息】
         ///  20181021
         /// </summary>
         /// <param name="obj"></param>
         private void SendMessage(object obj)
         {
             string[] data = (string[])obj;

             //字符串转16进制
             byte[] sendBytes = HexStringToByteArray(data[]);

             //发送到远程IP和端口
             IPEndPoint remoteIpep = new IPEndPoint(IPAddress.Parse(data[]), Convert.ToInt32(data[]));

             udpcSend.Send(sendBytes, sendBytes.Length, remoteIpep);

             ShowMessage(tbRecvMsg, "[Local Send]:" + data[]);
             ResetTextBox(tbSendMsg);
         }

         //构建远程服务的收发实例
         private UdpClient remoteUdpcSend;
         private UdpClient remoteUdpcRecv;
         private Thread remoteThrRecv;

         private Thread thrSend;
         private bool isRemoteCreated = false;
         /// <summary>
         /// 【发送消息】
         ///  20181021
         /// </summary>
         /// <param name="sender"></param>
         /// <param name="e"></param>
         private void btnSend_Click(object sender, EventArgs e)
         {
             if (string.IsNullOrWhiteSpace(tbRemoteIP.Text) || string.IsNullOrWhiteSpace(tbRemotePort.Text))
             {
                 MessageBox.Show("远程IP和端口不能为空！", "系统提示");
                 return;
             }

             if (string.IsNullOrWhiteSpace(tbSendMsg.Text))
             {
                 MessageBox.Show("发送的消息不能为空！", "系统提示");
                 return;
             }

             if (!isLocalConneted)
             {
                 MessageBox.Show("请先建立本地连接！", "系统提示");
                 return;
             }

             //构建本地远程
             if (cbIsRemoteAsLocal.Checked)//构建本地的远程服务，本地处理
             {
                 if (!isRemoteCreated)
                 {
                     IPEndPoint remoteIpep = new IPEndPoint(IPAddress.Parse(tbRemoteIP.Text), Convert.ToInt32(tbRemotePort.Text));//构建远程端口
                     remoteUdpcRecv = new UdpClient(remoteIpep);

                     //启动远程的监听
                     remoteThrRecv = new Thread(RemoteRecvMessage);
                     remoteThrRecv.Start();

                     ShowMessage(tbRecvMsg, "[OS]:Remote UDP 监听启动完成！");
                     isRemoteCreated = true;//远程服务已启动
                 }
                 else
                 {
                     //发送消息
                 }

             }
             else
             {
                 //发送消息,
             }

             //发送远程，这里不做处理，直接调用udpcSend发送即可
             thrSend = new Thread(new ParameterizedThreadStart(SendMessage));

             string[] param = new string[] { tbSendMsg.Text, tbRemoteIP.Text, tbRemotePort.Text };
             thrSend.Start(param);

         }

         /// <summary>
         /// 【本地远程发送消息】
         ///  20181021
         /// </summary>
         /// <param name="remoteIpep"></param>
         private void RemoteSendMessage(IPEndPoint remoteIpep)
         {
             remoteUdpcSend = remoteUdpcRecv;

             byte[] msg = Encoding.Default.GetBytes("远程已收到你的消息");

             remoteUdpcSend.Send(msg, msg.Length, remoteIpep);

             ShowMessage(tbRecvMsg, "[Remote Send]:" + "远程已收到你的消息");
         }

         /// <summary>
         /// 【本地远程接收信息】
         ///  20181021
         /// </summary>
         private void RemoteRecvMessage()
         {
             IPEndPoint remoteIpep = new IPEndPoint(IPAddress.Any, );//接收任何来源的信息
             while (true)
             {
                 byte[] byteRemoteRecv = remoteUdpcRecv.Receive(ref remoteIpep);
                 string message = Encoding.Default.GetString(byteRemoteRecv);

                 //接收到信息
                 if (byteRemoteRecv.Length > )
                 {
                     //remoteIpep.Address.ToString() 获取发送源的IP
                     ShowMessage(tbRecvMsg, "[Remote Recv]:" + remoteIpep.Address + ":" + remoteIpep.Port + "=" + message);

                     RemoteSendMessage(remoteIpep);
                 }

             }
         }

         //更新显示TextBox
         delegate void ShowMessageDelegate(TextBox tb, string msg);
         private void ShowMessage(TextBox tb, string msg)
         {
             if (tb.InvokeRequired)
             {
                 ShowMessageDelegate showMessageDelegate = ShowMessage;
                 tb.Invoke(showMessageDelegate, new object[] { tb, msg });
             }
             else
             {
                 tb.Text += msg + "\r\n";
             }
         }

         //清空TextBox
         delegate void ResetTextBoxDelegate(TextBox tb);
         private void ResetTextBox(TextBox tb)
         {
             if (tb.InvokeRequired)
             {
                 ResetTextBoxDelegate resetTextBoxDelegate = ResetTextBox;
                 tb.Invoke(resetTextBoxDelegate, new object[] { tb });
             }
             else
             {
                 tb.Text = "";
             }
         }

         /// <summary>
         /// 【字符串转16进制】
         ///  20181021
         /// </summary>
         /// <param name="s"></param>
         /// <returns></returns>
         public byte[] HexStringToByteArray(string s)
         {
             if (s.Length == )
                 throw new Exception("字符串长度为0");
             s = s.Replace(" ", "");
             byte[] buffer = new byte[s.Length / ];
             for (int i = ; i < s.Length; i += )
                 buffer[i / ] = Convert.ToByte(s.Substring(i, ), );
             return buffer;
         }

         /// <summary>
         /// 【字节数组转换成十六进制字符串(不带空格)】
         ///  20181021
         /// </summary>
         /// <param name="data">要转换的字节数组</param>
         /// <returns>转换后的字符串</returns>
         public string ByteArrayToHexStringNoBlank(byte[] data)
         {
             StringBuilder sb = new StringBuilder(data.Length * );
             foreach (byte b in data)
                 sb.Append(Convert.ToString(b, ).PadLeft(, '') + " ");
             return sb.ToString().ToUpper();
         }

         /// <summary>
         /// 【窗体退出，关闭子线程】
         ///  20181021
         /// </summary>
         /// <param name="sender"></param>
         /// <param name="e"></param>
         private void FrmMain_FormClosing(object sender, FormClosingEventArgs e)
         {
             Environment.Exit();
         }

     }
 }

二、界面