[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 != 0)
            {
                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, 0);//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[0]);

            //发送到远程IP和端口
            IPEndPoint remoteIpep = new IPEndPoint(IPAddress.Parse(data[1]), Convert.ToInt32(data[2]));

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

            
            ShowMessage(tbRecvMsg, "[Local Send]:" + data[0]);
            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, 0);//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 > 0)
                {
                    //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 + "
";
            }
        }

        //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 == 0)
                throw new Exception("字符串长度为0");
            s = s.Replace(" ", "");
            byte[] buffer = new byte[s.Length / 2];
            for (int i = 0; i < s.Length; i += 2)
                buffer[i / 2] = Convert.ToByte(s.Substring(i, 2), 16);
            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 * 3);
            foreach (byte b in data)
                sb.Append(Convert.ToString(b, 16).PadLeft(2, '0') + " ");
            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(0);
        }

 


    }
}

二、界面