/// SERVER 
using System;
using System.Threading.Tasks;
using System.Windows.Forms;

// https://dobon.net/vb/dotnet/internet/tcpclientserver.html
namespace sertcp {

    public partial class Form1 : Form {

        static System.Net.Sockets.TcpClient client;
        static System.Net.Sockets.NetworkStream ns;
        static System.Text.Encoding enc; 


        public Form1() {
            InitializeComponent();

            Start();
        }

        private async void Start() {

            textBox1.Text = "SERVER START\r\n";
            string ipString = "127.0.0.1";
            int port = 2001;
            System.Net.IPAddress ipAdd = System.Net.IPAddress.Parse(ipString);
           

            //TcpListenerオブジェクトを作成する
            System.Net.Sockets.TcpListener listener = new System.Net.Sockets.TcpListener(ipAdd, port);

            //Listenを開始する
            listener.Start();
            textBox1.Text = "listener start\r\n" + textBox1.Text;

            //接続要求があったら受け入れる
            await Task.Run(() => {
                client = listener.AcceptTcpClient();
            });
            textBox1.Text += "connect\r\n";

            textBox1.Text += (((System.Net.IPEndPoint)client.Client.RemoteEndPoint).Address).ToString() + "\r\n";
            textBox1.Text += (((System.Net.IPEndPoint)client.Client.RemoteEndPoint).Port).ToString() + "\r\n";


            //NetworkStreamを取得
            ns = client.GetStream();

            enc = System.Text.Encoding.UTF8;
            byte[] resBytes = new byte[256];
            int resSize = 0;

            while (true) {
                System.IO.MemoryStream ms = new System.IO.MemoryStream();

                await Task.Run(() => {

                    do {
                        //データの一部を受信する
                        try {
                            resSize = ns.Read(resBytes, 0, resBytes.Length);
                        }
                        catch (System.IO.IOException e) {
                            MessageBox.Show(e.Message);
                            continue;
                        }

                        //受信したデータを蓄積する
                        ms.Write(resBytes, 0, resSize);

              
                    } while (ns.DataAvailable || resBytes[resSize - 1] != '\n');
                });

                string resMsg = enc.GetString(ms.GetBuffer(), 0, (int)ms.Length);
                ms.Close();

               
                resMsg = resMsg.TrimEnd('\n');
                textBox1.Text = resMsg + "\r\n" + textBox1.Text;
            }
        }

        // SEND                             
        private async void button1_Click(object sender, EventArgs e) {

            while (true) {
                
                byte[] sendBytes = enc.GetBytes(textBox2.Text + '\n');
            
                await Task.Run(() => {
                    ns.Write(sendBytes, 0, sendBytes.Length);
                });
                textBox2.Text = "";
                break;
            }
        }

    }
}

/////////////////////////////////////////////////////////////////////////////////////////////////
// CLIENT
using System;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace clitcp {
    public partial class Form1 : Form {

        public static System.Net.Sockets.NetworkStream ns;
        public static System.Text.Encoding enc = System.Text.Encoding.UTF8;
        
        string ipOrHost = "127.0.0.1";
        //string ipOrHost = "localhost";
        int port = 2001;
        
        public Form1() {
            InitializeComponent();

            try { 
                System.Net.Sockets.TcpClient tcp = new System.Net.Sockets.TcpClient(ipOrHost, port);
                ns = tcp.GetStream();
            }
            catch(System.Net.Sockets.SocketException e){
                textBox2.Text=e.Message;
                return;
            }
         
            Recv();

        }


        // SEND
        private async void button1_Click(object sender, EventArgs e) {

            while (true) {
                byte[] sendBytes = enc.GetBytes(textBox1.Text + '\n');

                await Task.Run(() => {
                    ns.Write(sendBytes, 0, sendBytes.Length);
                });

                textBox1.Text = "";
                break;
            }

        }


        // RECV
        private async void Recv() {

            while (true) {
                
                System.IO.MemoryStream ms = new System.IO.MemoryStream();
                enc = System.Text.Encoding.UTF8;
                byte[] resBytes = new byte[256];
                int resSize = 0;

                await Task.Run(() => {

                    do {
                        //データの一部を受信する
                        try {
                            resSize = ns.Read(resBytes, 0, resBytes.Length);
                        }
                        catch (System.IO.IOException e) {
                            MessageBox.Show(e.Message);
                            continue;
                        }

                        //受信したデータを蓄積する
                        ms.Write(resBytes, 0, resSize);


                    } while (ns.DataAvailable || resBytes[resSize - 1] != '\n');
                });

                string resMsg = enc.GetString(ms.GetBuffer(), 0, (int)ms.Length);
                ms.Close();


                resMsg = resMsg.TrimEnd('\n');

                textBox2.Text = resMsg + "\r\n" + textBox2.Text;
            }
                                                                                                                                        
        }

    }
}