In my network programming class CS3670 at UVU (UVSC) we had an assignment to write a multicast chat program that would allow everyone in the class talk in the same chat window. This was used to show that we were able to use the multicast addresses and to also demonstrate our use of the UDP client libraries. Here is my solution:
1 using System;
2 using System.Collections.Generic;
3 using System.ComponentModel;
4 using System.Data;
5 using System.Drawing;
6 using System.Text;
7 using System.Windows.Forms;
8 using System.Net;
9 using System.Net.Sockets;
10 using System.Threading;
11
12 namespace MultiCastChat
13 {
14 public partial class formMain : Form
15 {
16 private const int TIME_TO_LIVE = 50;
17 private UdpClient client = null;
18 private IPAddress group = null;
19 private int port = 0;
20 private IPEndPoint multiCastEP = null;
21
22 private bool stayAlive = true;
23 private Thread receiveThread = null;
24 private string defaultNameText = "";
25
26 public delegate void dListOngoing(string message);
27 public dListOngoing listOngoing;
28
29 public formMain()
30 {
31 InitializeComponent();
32 }
33
34 private void formMain_Load(object sender, EventArgs e)
35 {
36 comboAddress.SelectedIndex = 0;
37 defaultNameText = textboxName.Text;
38 this.AcceptButton = buttonJoin;
39 this.CancelButton = buttonExit;
40 this.buttonJoin.Enabled = true;
41 this.buttonExit.Enabled = true;
42 this.buttonSend.Enabled = true;
43 this.textboxPort.Text = "" + 10002;
44 textboxInput.Focus();
45 listOngoing = new dListOngoing(displayMessage);
46 }
47
48 private void buttonSend_Click(object sender, EventArgs e)
49 {
50 this.SendMessage(textboxInput.Text);
51 }
52
53 private void buttonEnd_Click(object sender, EventArgs e)
54 {
55 this.LeaveGroup();
56
57 buttonJoin.Enabled = true;
58 buttonEnd.Enabled = false;
59 buttonSend.Enabled = false;
60 this.AcceptButton = buttonJoin;
61 this.CancelButton = buttonExit;
62 }
63
64 private void SendMessage(String message)
65 {
66 Byte[] buff;
67
68 buff = Encoding.ASCII.GetBytes(textboxName.Text + ": " + message);
69 client.Send(buff, buff.Length, multiCastEP);
70 textboxInput.Text = "";
71 }
72
73 private void LeaveGroup()
74 {
75 if (group != null)
76 {
77 SendMessage("Leaving Chat");
78 Application.DoEvents();
79 Thread.Sleep(500);
80 stayAlive = false;
81 while (receiveThread.IsAlive) Application.DoEvents();
82 receiveThread.Join();
83 client.DropMulticastGroup(group);
84 client.Close();
85 client = null;
86 group = null;
87 multiCastEP = null;
88 }
89 }
90
91 private void JoinGroup()
92 {
93 if (!int.TryParse(textboxPort.Text, out port))
94 throw new ApplicationException("Invalid Port Number");
95 if (!IPAddress.TryParse(comboAddress.Text, out group))
96 throw new ApplicationException("Invalid Multicast Group Address");
97
98 client = new UdpClient(port);
99 client.JoinMulticastGroup(group, TIME_TO_LIVE);
100 multiCastEP = new IPEndPoint(group, port);
101
102 this.stayAlive = true;
103 receiveThread = new Thread(this.runThread);
104 receiveThread.Start();
105
106 this.SendMessage("has joined the chat!");
107 this.AcceptButton = buttonSend;
108 this.CancelButton = buttonEnd;
109 this.buttonJoin.Enabled = false;
110 this.buttonEnd.Enabled = true;
111 this.buttonSend.Enabled = true;
112 textboxInput.Focus();
113 }
114
115 private void runThread()
116 {
117 Byte[] buff;
118 String message;
119 while (stayAlive)
120 {
121 IPEndPoint ep = null;
122 if (client.Available > 0)
123 {
124 buff = client.Receive(ref ep);
125 message = Encoding.ASCII.GetString(buff);
126 this.Invoke(this.listOngoing, message);
127 }
128 else
129 {
130 Thread.Sleep(10);
131 }
132 }
133 }
134
135 private void buttonExit_Click(object sender, EventArgs e)
136 {
137 this.LeaveGroup();
138 buttonJoin.Enabled = true;
139 buttonEnd.Enabled = false;
140 buttonSend.Enabled = false;
141 this.AcceptButton = buttonJoin;
142 this.CancelButton = buttonExit;
143 this.Close();
144 }
145
146 public void displayMessage(string message)
147 {
148 lstOngoing.Items.Add(message);
149 lstOngoing.Refresh();
150 }
151
152 private void buttonJoin_Click(object sender, EventArgs e)
153 {
154 this.JoinGroup();
155 }
156 }
157 }
Here is a screen shot of my application connected to another member of the class.
