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

namespace ProjectChatApps
{
    public partial class Form1 : Form
    {
        Socket sck;
        EndPoint epLocal, epRemote;
        byte[] buffer;
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            //set up socket,
            sck = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
            sck.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true);
            // get user IP
            textLocalIp.Text = GetLocalIP();
            textRemoteIp.Text = GetLocalIP();

        }
        private string GetLocalIP()
        {
            IPHostEntry host;
            host=Dns.GetHostEntry(Dns.GetHostName());
            foreach(IPAddress ip in host.AddressList)
            {
                if(ip.AddressFamily==AddressFamily.InterNetwork)
                    return ip.ToString();
            }
            return "";
        }

        private void buttonConnect_Click(object sender, EventArgs e)
        {
            // binding socket
            epLocal = new IPEndPoint(IPAddress.Parse(textLocalIp.Text), Convert.ToInt32(textLocalPort.Text));
            sck.Bind(epLocal);
            //conecting to remote IP
            epRemote = new IPEndPoint(IPAddress.Parse(textRemoteIp.Text), Convert.ToInt32(textRemotePort.Text));
            sck.Connect(epRemote);
            //Listening the specific port
            buffer=new byte[1500];
            sck.BeginReceiveFrom(buffer,0,buffer.Length,SocketFlags.None,ref epRemote,new AsyncCallback(MessageCallBack),buffer);

        }
        private void MessageCallBack(IAsyncResult aResult)
        {
            try
            {
            byte[] receivedData = new byte[1500];
            receivedData = (byte[])aResult.AsyncState;
            //converting byte[] tostring
            ASCIIEncoding aEncoding = new ASCIIEncoding();
            String receivedMessage=aEncoding.GetString(receivedData);
            //adding this message into listbox
            listMessage.Items.Add("Friend: "+receivedMessage);
            buffer = new byte[1500];
            sck.BeginReceiveFrom(buffer,0,buffer.Length,SocketFlags.None,ref epRemote,new AsyncCallback(MessageCallBack),buffer);
            }
            catch(Exception ex)
            {
                MessageBox.Show(ex.ToString());
            }
        }

        private void buttonSend_Click(object sender, EventArgs e)
        {
            //Convert string message to byte[]
            ASCIIEncoding aEncoding = new ASCIIEncoding();
            byte[] sendingMessage = new byte[1500];
            sendingMessage= aEncoding.GetBytes(textMessage.Text);
            //Sending
            sck.Send(sendingMessage);
            //adding to listbox
            listMessage.Items.Add("Me: "+textMessage.Text);
            textMessage.Text="";
        }
    }
}


เช่น
A; สวัสดี

เเล้วมันขึ้นที่ฟอร์มเพื่อนว่า
A; ????
มันไม่ขึ้นเป็นภาษาไทย เเต่ภาษาENGขึ้นปกติ