以下程式碼來源於《C#網路程式設計技術教程》。

 1     public class UDPComm
 2     {
 3         public static byte[] EncodingASCII(string buf)//編碼
 4         {
 5             byte[] data = Encoding.ASCII.GetBytes(buf + "\r\n");
 6             return data;
 7         }
 8         public static string DecodingASCII(byte
 
[] buf)//解碼
 9         {
10             string st = Encoding.ASCII.GetString(buf);
11             return st;
12         }
13     }

 1 class UDPServer
 2     {
 3         static UdpClient m_server;
 4         static ArrayList mblist;
 5 
 6         static void AddMember(IPEndPoint rep)//
 
加入組
 7         {
 8             mblist.Add(rep);
 9             byte[] data = UDPComm.EncodingASCII("OK");
10             m_server.Send(data, data.Length, rep);
11         }
12         static void DelMember(IPEndPoint rep)//離開組
13         {
14             mblist.Remove(rep);
15             byte[] data = UDPComm.EncodingASCII("
 
OK");
16             m_server.Send(data, data.Length, rep);
17 
18         }
19         static void SendToMember(string buf)//組內轉發資料
20         {
21             foreach (IPEndPoint mb in mblist)
22             {
23                 byte[] data = UDPComm.EncodingASCII(buf);
24                 m_server.Send(data, data.Length, mb);
25             }
26         }
27 
28         static void Main(string[] args)
29         {
30             string m_hostIP = "127.0.0.1";
31             int m_port = 6666;
32             IPEndPoint m_EndPoint;
33             ArrayList memberlist = new ArrayList();
34             bool rt = false;
35             byte[] data;
36             string m_ReturnData;
37 
38             //從命令列提取主機IP和埠
39             if (args.Length < 2)
40             {
41                 Console.WriteLine("Usage: UDPServer hostIP port");
42             }
43             else
44             {
45                 m_hostIP = args[0].ToString();
46                 m_port = int.Parse(args[1].ToString());
47                 rt = true;
48             }
49 
50             if (rt)
51             {
52                 mblist = new ArrayList();//組成員列表
53 
54                 IPAddress m_ipA = IPAddress.Parse(m_hostIP);
55                 m_EndPoint = new IPEndPoint(m_ipA, m_port);
56                 m_server = new UdpClient(m_EndPoint);
57 
58                 Console.WriteLine("Ready for Connect......");
59                 while (true)
60                 {
61                     data = m_server.Receive(ref m_EndPoint);//接收資料
62                     m_ReturnData = UDPComm.DecodingASCII(data);
63 
64                     if (m_ReturnData.IndexOf("ADD") > -1)//加入組
65                     {
66                         AddMember(m_EndPoint);
67                         Console.WriteLine(m_EndPoint.ToString() + "has added to group");
68                     }
69                     else if (m_ReturnData.IndexOf("DEL") > -1)//退出組
70                     {
71                         DelMember(m_EndPoint);
72                         Console.WriteLine(m_EndPoint.ToString() + "has delete from group");
73                     }
74                     else
75                     {
76                         if (mblist.Contains(m_EndPoint))//轉發資料
77                         {
78                             SendToMember(m_ReturnData + "[" + m_EndPoint.ToString() + "]");
79                             Console.WriteLine(m_ReturnData + "[" + m_EndPoint.ToString() + "]"
80                                 + "has resented to member");
81                         }
82                     }
83                 }
84                 m_server.Close();
85             }
86         }
87     }

 1 class UDPClient
 2     {
 3         static void Main(string[] args)
 4         {
 5             string m_hostIP = "127.0.0.1";
 6             int m_port = 6666;
 7             UdpClient m_client;
 8             bool rt = false;
 9             byte[] data;
10             string m_SendData, m_ReturnData;
11             IPEndPoint m_EndPoint;
12 
13             //從命令列提取伺服器地址和偵聽埠
14             if (args.Length < 2)
15             {
16                 Console.WriteLine("Usage: UDPClient hostIP port");
17             }
18             else
19             {
20                 m_hostIP = args[0].ToString();
21                 m_port = int.Parse(args[1].ToString());
22                 rt = true;
23             }
24 
25             if (rt)
26             {
27                 IPAddress m_ipA = IPAddress.Parse(m_hostIP);
28                 m_EndPoint = new IPEndPoint(m_ipA, m_port);
29 
30                 IPAddress m_ipA1 = IPAddress.Parse("127.0.0.1");
31                 IPEndPoint m_EndPoint1 = new IPEndPoint(m_ipA1, 8060);
32                 //m_client = new UdpClient(); 不繫結本地終結點，系統將會隨機分配一個終結點
33                 m_client = new UdpClient(m_EndPoint1);
34                 
35                 m_client.Connect(m_EndPoint);
36 
37                 while (true)
38                 {
39                     Console.WriteLine("Input [ADD|DEL|REF|QUIT|Message]:");
40                     m_SendData = Console.ReadLine();
41 
42                     if(m_SendData.IndexOf("QUIT")>-1)//退出
43                     {
44                         m_SendData = "DEL";
45                     }
46 
47                     if(m_SendData.IndexOf("REF")<=-1)//重新整理顯示
48                     {
49                         data = UDPComm.EncodingASCII(m_SendData);
50                         m_client.Send(data, data.Length);
51                     }
52                     if (m_SendData.IndexOf("QUIT") > -1)
53                         break;
54 
55                     data = m_client.Receive(ref m_EndPoint);
56                     Console.WriteLine(m_EndPoint.ToString());
57                     m_ReturnData = UDPComm.DecodingASCII(data);
58                     Console.WriteLine(m_ReturnData);
59                 }
60                 //退出
61                 Console.WriteLine("Byte!");
62                 m_client.Close();
63             }
64         }
65     }