Question

I have a homework to build an application which will send and receive simple string between server and client. I know how to establish connection, but don’t know how to send and receive string. This is my code :

public partial class Form1 : Form
{
    private Thread n_server;
    private Thread n_client;
    private Thread n_send_server;
    private TcpClient client;
    private TcpListener listener;
    private int port = 2222;
    private string IP = " ";
    private Socket socket;
    public Form1()
    {
        InitializeComponent();
    }

    private void exitToolStripMenuItem_Click(object sender, EventArgs e)
    {
        Application.Exit();
    }

    public void Server()
    {
        listener = new TcpListener(IPAddress.Any, port);
        listener.Start();
        try
        {
            socket = listener.AcceptSocket();
            if (socket.Connected)
            {
                textBox2.Invoke((MethodInvoker)delegate { textBox2.Text = "Client : " + socket.RemoteEndPoint.ToString(); });
            }
        }
        catch
        {
        }
    }

    public void Client()
    {
        IP = "localhost";
        client = new TcpClient();
        try
        {
            client.Connect(IP, port);
        }

        catch (Exception ex)
        {
            MessageBox.Show("Error : " + ex.Message);
        }

        if (client.Connected)
        {
            textBox3.Invoke((MethodInvoker)delegate { textBox3.Text = "Connected..."; });

        }
    }

    private void button1_Click(object sender, EventArgs e)
    {
        n_server = new Thread(new ThreadStart(Server)); 
        n_server.IsBackground = true;
        n_server.Start();
        textBox1.Text = "Server up";
    }

    private void button2_Click(object sender, EventArgs e)
    {
        n_client = new Thread(new ThreadStart(Client));
        n_client.IsBackground = true;
        n_client.Start();
    }

    private void send()
    {
        // I want to use this method for both buttons : "send button" on server side    and "send button"
        // on client side. First I read text from textbox2 on server side or textbox3
        // on client side than accept and write the string to label2(s) or label3(c).
        // 
    }


    private void button3_Click(object sender, EventArgs e)
    {
        n_send_server = new Thread(new ThreadStart(send));
        n_send_server.IsBackground = true;
        n_send_server.Start();
    }
}

Answer 1

The following code send and recieve the current date and time from and to the server

//The following code is for the server application:

namespace Server
{
    class Program
    {
        const int PORT_NO = 5000;
        const string SERVER_IP = "127.0.0.1";

        static void Main(string[] args)
        {
            //---listen at the specified IP and port no.---
            IPAddress localAdd = IPAddress.Parse(SERVER_IP);
            TcpListener listener = new TcpListener(localAdd, PORT_NO);
            Console.WriteLine("Listening...");
            listener.Start();

            //---incoming client connected---
            TcpClient client = listener.AcceptTcpClient();

            //---get the incoming data through a network stream---
            NetworkStream nwStream = client.GetStream();
            byte[] buffer = new byte[client.ReceiveBufferSize];

            //---read incoming stream---
            int bytesRead = nwStream.Read(buffer, 0, client.ReceiveBufferSize);

            //---convert the data received into a string---
            string dataReceived = Encoding.ASCII.GetString(buffer, 0, bytesRead);
            Console.WriteLine("Received : " + dataReceived);

            //---write back the text to the client---
            Console.WriteLine("Sending back : " + dataReceived);
            nwStream.Write(buffer, 0, bytesRead);
            client.Close();
            listener.Stop();
            Console.ReadLine();
        }
    }
}

//this is the code for the client

namespace Client
{
    class Program
    {
        const int PORT_NO = 5000;
        const string SERVER_IP = "127.0.0.1";
        static void Main(string[] args)
        {
            //---data to send to the server---
            string textToSend = DateTime.Now.ToString();

            //---create a TCPClient object at the IP and port no.---
            TcpClient client = new TcpClient(SERVER_IP, PORT_NO);
            NetworkStream nwStream = client.GetStream();
            byte[] bytesToSend = ASCIIEncoding.ASCII.GetBytes(textToSend);

            //---send the text---
            Console.WriteLine("Sending : " + textToSend);
            nwStream.Write(bytesToSend, 0, bytesToSend.Length);

            //---read back the text---
            byte[] bytesToRead = new byte[client.ReceiveBufferSize];
            int bytesRead = nwStream.Read(bytesToRead, 0, client.ReceiveBufferSize);
            Console.WriteLine("Received : " + Encoding.ASCII.GetString(bytesToRead, 0, bytesRead));
            Console.ReadLine();
            client.Close();
        }
    }
}