<C#>最简单的NetMeeting

      怎样制造小画家软件了，怎样实现小画家在互联电脑间显示update了？其实，应用的方法很简单。我们可用Form中的一些事件来浅浅介绍一下：在客户端用上Form中的MouseDown和MouseUp两个事件做出小画家来，通过UDP协议将小画家中信息即时发送去服务端。客户端的代码如下：

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

namespace Client3
{
    public partial class Form1 : Form
    {
        int startX, startY,stopX,stopY;
        Graphics g;

        Socket s = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
        IPEndPoint ipep = new IPEndPoint(IPAddress.Parse("127.0.0.1"), 9050);

        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            if (Enabled == false)
                s.Close();
        }

        private void Form1_MouseDown(object sender, MouseEventArgs e)
        {
            startX = e.X;
            startY = e.Y;

            byte[] mybyte1 = Encoding.Default.GetBytes(Convert.ToString(startX));
            byte[] mybyte2 = Encoding.Default.GetBytes(Convert.ToString(startY));
            s.SendTo(mybyte1, ipep);
            s.SendTo(mybyte2, ipep);

        }

        private void Form1_MouseUp(object sender, MouseEventArgs e)
        {
            g = this.CreateGraphics();
            Pen p = new Pen(Color.Red, 1);
            g.DrawLine(p, startX, startY, e.X, e.Y);

            stopX = e.X;
            stopY = e.Y;

            byte[] mybyte3 = Encoding.Default.GetBytes(Convert.ToString(stopX));
            byte[] mybyte4 = Encoding.Default.GetBytes(Convert.ToString(stopY));
            s.SendTo(mybyte3, ipep);
            s.SendTo(mybyte4, ipep);


        }
        //    s.Close();     
    }
}

在服务器端用Form中的Paint事件将客户端接受来的信息显示到Form中。它的代码如下：

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

namespace Service3
{
    public partial class Form1 : Form
    {
        int startX, startY, stopX, stopY;
        Graphics g;

        Socket s = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
        IPEndPoint ipep = new IPEndPoint(IPAddress.Any, 9050);

        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            if (Enabled == false)
                s.Close();
        }

        private void Form1_Paint(object sender, PaintEventArgs e)
        {
            s.Bind(ipep);

            while (true)
            {
                byte[] data1 = new byte[1024];
                IPEndPoint send1 = new IPEndPoint(IPAddress.Any, 0);
                EndPoint Remote1 = (EndPoint)(send1);
                int length1 = s.ReceiveFrom(data1, ref Remote1);
                startX = Convert.ToInt32(Encoding.Default.GetString(data1, 0, length1));

                byte[] data2 = new byte[1024];
                IPEndPoint send2 = new IPEndPoint(IPAddress.Any, 0);
                EndPoint Remote2 = (EndPoint)(send2);
                int length2 = s.ReceiveFrom(data2, ref Remote2);
                startY = Convert.ToInt32(Encoding.Default.GetString(data2, 0, length2));

                byte[] data3 = new byte[1024];
                IPEndPoint send3 = new IPEndPoint(IPAddress.Any, 0);
                EndPoint Remote3 = (EndPoint)(send3);
                int length3 = s.ReceiveFrom(data3, ref Remote3);
                stopX = Convert.ToInt32(Encoding.Default.GetString(data3, 0, length3));

                byte[] data4 = new byte[1024];
                IPEndPoint send4 = new IPEndPoint(IPAddress.Any, 0);
                EndPoint Remote4 = (EndPoint)(send4);
                int length4 = s.ReceiveFrom(data4, ref Remote4);
                stopY = Convert.ToInt32(Encoding.Default.GetString(data4, 0, length4));

                g = e.Graphics;
                Pen pen1 = new Pen(Color.Blue, 1);
                g.DrawLine(pen1, startX, startY, stopX, stopY);
            }
            
            //s.Close();
        }

    }
}