Client

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
    {
        private static Socket clientSocket;
        private const string HostName = "localhost";
        private const int PortNumber = 2000;
        byte[] buffer = new byte[1024];
        public Form1()
        {
            InitializeComponent();
            clientSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            ConnectToServer();
        }
        private void ConnectToServer()
        {
            try
            {
                clientSocket.Connect("192.168.0.11", 2000);

                AddMessage("Connected to server");

                clientSocket.BeginReceive(buffer, 0, 1024, 0, new AsyncCallback(ReceiveCallback), clientSocket);
            }
            catch (Exception)
            {
                AddMessage("Unable to connect to server");
            }
        }

        private void DisconnectFromServer()
        {
            ClearMessageList();
            AddMessage("Disconnected from server");
        }

        public void ReceiveCallback(IAsyncResult asyncResult)
        {
            Socket client = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);

            try
            {
                client = clientSocket.EndAccept(asyncResult);
                if (client.Connected)
                {
                    int bytesRead = client.EndReceive(asyncResult);
                    if (bytesRead > 0) AddMessage(Encoding.ASCII.GetString(buffer, 0, bytesRead));
                    client.BeginReceive(buffer, 0, 1024, 0, new AsyncCallback(ReceiveCallback), client);
                }
            }
            catch (Exception)
            {
                DisconnectFromServer();
            }
        }

        private void AddMessage(string message)
        {
            messageList.Invoke((MethodInvoker)delegate ()
            {
                messageList.Items.Add(message);
            });
        }
        private void ClearMessageBox()
        {
            messageBox.Invoke((MethodInvoker)delegate ()
            {
                messageBox.Text = String.Empty;
            });
        }

        private void ClearMessageList()
        {
            messageList.Invoke((MethodInvoker)delegate ()
            {
                messageList.Items.Clear();
            });
        }
        private void SendButtonOnClick(object sender, EventArgs e)
        {
            string message = messageBox.Text;
            ClearMessageBox();
            clientSocket.Send(Encoding.ASCII.GetBytes(message));
        }
    }
}