sever

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;
using System.Threading;

namespace Tuan3_Bai1
{

    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        private void Form1_Load(object sender, EventArgs e)
        {
            CheckForIllegalCrossThreadCalls = false;
        }

        /*********** Data structure ***********/
        public IPAddress ipAd;
        public int port;
        public TcpListener server;
        public int count = 0;
        public Socket[] socket = new Socket[100];
        public string[] sum = new string[100];
        public List<int> isUsed = new List<int>();
        public bool check = true;
        private void Btn_Start_Click(object sender, EventArgs e)
        {
            Btn_Start.Enabled = false;
            StartServer();
            //serves multiple clients
            Thread t = new Thread(connect);
            t.IsBackground = true;
            t.Start();
        }
        public void StartServer()
        {
            ipAd = IPAddress.Parse(txt_IP.Text);
            port = int.Parse(txt_Port.Text);
            server = new TcpListener(ipAd, port);
            server.Start();
            count = 0;
        }

        public int testconnect(Socket socket)
        {
            return 0;
        }
        //Threading

        public void connect()
        {
            while (true)
            {
                //accept a new connection
                socket[count] = server.AcceptSocket();

                count++;//should use lock here
                //break main flow into main + ServeClientConcurrently flow
                isUsed.Add(1);
                if (check != true)
                {
                    int pos = 0;
                    foreach (int i in isUsed)
                    {
                        if (i == 0)
                        {
                            count = pos+1;
                            break;
                        }
                        pos++;
                    }
                    isUsed[pos] = 1;
                    check = true;
                }
                Thread t = new Thread(ServeClientConcurrently);
                t.Start(count-1);
                txt_QLKN.AppendText("Client " + (count ) + " connect" + "\n");
            }
        }
        public void ServeClientConcurrently(object obj)
        {
            //get correct socket
            int index = (Int32)obj;
            while (true)
            {
                byte[] b = new byte[100];
                //string temp = socket[index].RemoteEndPoint.ToString();
                try
                {
                    int k = socket[index].Receive(b);
                }
                catch
                {
                    socket[index].Close();
                    isUsed[index] = 0;
                    check = false;
                    txt_QLKN.AppendText("Client " + (index + 1) + " disconnect" + "\n");
                    return;
                }

                string abc = Encoding.ASCII.GetString(b);
                sum[index] = SumFun(abc);
                Txt_QLTV.AppendText("Yêu cầu từ client " + (index + 1).ToString() + "\n");
                Txt_QLTV.AppendText("Kết quả: " + sum[index] + "\n");
                ASCIIEncoding asen = new ASCIIEncoding();
                socket[index].Send(asen.GetBytes(sum[index]));
            }
        }

        public string SumFun(string str)
        {
            string[] strS = str.Split('/');
            int x1 = int.Parse(strS[0]);
            int x2 = int.Parse(strS[1]);
            int sum = x1 + x2;
            return sum.ToString();
        }
    }
}