How to make the IP to the computer's IP in the TCP Server?

Question

How to make the IP to the computer's IP in the TCP Server?
I created a chat but every time you open the software the IP changes, so I want to make the IP the IP of the computer or the IP be fixed
the server code:

using SimpleTcp;
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;

namespace TCPServer
{
    public partial class Form1 : Form
    {
        int frindNum;
        string ChooseClient = "127.0.0.1:9000";
        public Form1()
        {
            InitializeComponent();
        }

        public SimpleTcpServer server;

        private void btnStart_Click(object sender, EventArgs e)
        {
            server.Start();
            btnSend.Enabled = false;
            txtInfo.Text += $"starting...{Environment.NewLine}";
            btnStart.Enabled = false;
            btnSend.Enabled = true;
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            btnSend.Enabled = false;
            server = new SimpleTcpServer(txtIP.Text);
            server.Events.ClientConnected += Events_ClientConnected;
            server.Events.ClientDisconnected += Events_ClientDisconnected;
            server.Events.DataReceived += Events_DataReceived;
        }

        private void Events_DataReceived(object sender, DataReceivedEventArgs e)
        {

            this.Invoke((MethodInvoker)delegate
            {

                if (Encoding.UTF8.GetString(e.Data).Contains("127.0.0.1:"))
                {
                    lstClientIP.SelectedItem = Encoding.UTF8.GetString(e.Data);
                }

                if (!Encoding.UTF8.GetString(e.Data).Contains("127.0.0.1:"))
                {
                    txtInfo.Text += $"{e.IpPort}: {Encoding.UTF8.GetString(e.Data)} {Environment.NewLine}";
                    server.Send(lstClientIP.SelectedItem.ToString(), Encoding.UTF8.GetString(e.Data));
                }




            });
        }

        private void Events_ClientDisconnected(object sender, ClientDisconnectedEventArgs e)
        {
            this.Invoke((MethodInvoker)delegate
            {
                server.Send(lstClientIP.SelectedItem.ToString(), txtMessage.Text);
                txtInfo.Text += $"{e.IpPort} disconnected.{Environment.NewLine}";
                lstClientIP.Items.Remove(e.IpPort);
                frindNum -= 1;


            });

        }

        private void Events_ClientConnected(object sender, ClientConnectedEventArgs e)
        {

            this.Invoke((MethodInvoker) delegate 
            {
                frindNum += 1;
                txtInfo.Text += $"{e.IpPort} connected.{Environment.NewLine}";
                lstClientIP.Items.Add(e.IpPort);

                server.Send(e.IpPort, e.IpPort);

            });

        }

        private void btnSend_Click(object sender, EventArgs e)
        {
            if (server.IsListening)
            {
                if(!string.IsNullOrEmpty(txtMessage.Text) && lstClientIP.SelectedItem != null)
                {

                    server.Send(lstClientIP.SelectedItem.ToString(), txtMessage.Text);

                    txtInfo.Text += $"server: {txtMessage.Text}{Environment.NewLine}";
                }
            }
        }

        private void lstClientIP_SelectedIndexChanged(object sender, EventArgs e)
        {

        }

        private void txtMessage_TextChanged(object sender, EventArgs e)
        {

        }
    }
}

the client code:

using SimpleTcp;
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;


namespace TCP_Client
{
    public partial class Form1 : Form
    {

        public Form1()
        {
            InitializeComponent();
        }

        SimpleTcpClient client;
        int locY;

        private void btnConnect_Click(object sender, EventArgs e)
        {
            try
            {
                client.Connect();
                btnSend.Enabled = true;
                btnConnect.Enabled = false;
            }
            catch(Exception ex)
            {
                MessageBox.Show(ex.Message, "messege", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            client = new(txtIP.Text);
            client.Events.Connected += Events_ClientConnected;
            client.Events.DataReceived += Events_DataReceived;
            client.Events.Disconnected += Events_ClientDisconnected;


            btnSend.Enabled = false;



        }



        private void Events_ClientDisconnected(object sender, ClientDisconnectedEventArgs e)
        {
            this.Invoke((MethodInvoker)delegate
            {
                txtInfo.Text += $"server disconected.{Environment.NewLine}";

            });
        }

        private void Events_DataReceived(object sender, DataReceivedEventArgs e)
        {

            this.Invoke((MethodInvoker)delegate
            {
                //txtInfo.Text += $"fraind: {Encoding.UTF8.GetString(e.Data)} {Environment.NewLine}";

                locY += 51;
                Label tb = new Label();
                tb.Location = new Point(label5.Location.X, locY);
                tb.Text = $"fraind: {Encoding.UTF8.GetString(e.Data)} {Environment.NewLine}";
                tb.Size = label5.Size;
                tb.BackColor = label5.BackColor;
                Panel pe = new Panel();
                pe.Location = new Point(panel5.Location.X, locY - 8);
                pe.Size = panel5.Size;
                pe.BackColor = panel5.BackColor;
                pe.BackgroundImageLayout = panel5.BackgroundImageLayout;
                pe.BackgroundImage = panel5.BackgroundImage;
                Controls.Add(tb);
                Controls.Add(pe);
                pe.Parent = panel4;
                tb.Parent = panel4;
                pe.BringToFront();
                tb.BringToFront();

                if (Encoding.UTF8.GetString(e.Data).Contains("127.0.0.1:"))
                {
                    label3.Text = Encoding.UTF8.GetString(e.Data);

                }
            });

        }

        private void Events_ClientConnected(object sender, ClientConnectedEventArgs e)
        {
            this.Invoke((MethodInvoker)delegate
            {
                txtInfo.Text += $"server conected.{Environment.NewLine}";
                btnSend.Enabled = false;
                btnConnect.Enabled = false;
                label3.Text = "none";


            });



        }

        private void btnSend_Click(object sender, EventArgs e)
        {
            if (client.IsConnected)
            {

                if (!string.IsNullOrEmpty(txtMessage.Text))
                {

                    client.Send(txtMessage.Text);

                    //txtInfo.Text += $"me: {txtMessage.Text}{Environment.NewLine}";

                    locY += 51;
                    Label tb = new Label();
                    tb.Location = new Point(label4.Location.X, locY - 2);
                    tb.Text = $"me: {txtMessage.Text}{Environment.NewLine}";
                    tb.Size = label4.Size;
                    tb.BackColor = label4.BackColor;
                    Panel pe = new Panel();
                    pe.Location = new Point(panel3.Location.X, locY - 8);
                    pe.Size = panel3.Size;
                    pe.BackColor = panel3.BackColor;
                    pe.BackgroundImageLayout = panel3.BackgroundImageLayout;
                    pe.BackgroundImage = panel3.BackgroundImage;
                    Controls.Add(tb);
                    Controls.Add(pe);
                    pe.Parent = panel4;
                    tb.Parent = panel4;
                    pe.BringToFront();
                    tb.BringToFront();

                    panel4.Size += new Size(0, 25);

                    txtMessage.Text = string.Empty;
                }
            }
        }

        private void lstClientIP_SelectedIndexChanged(object sender, EventArgs e)
        {
            client.Send(lstClients.SelectedItem.ToString());
        }

        private void label2_Click(object sender, EventArgs e)
        {

        }

        private void button1_Click(object sender, EventArgs e)
        {
            lstClients.Items.Add(textBox1.Text);
        }

        private void textBox1_TextChanged(object sender, EventArgs e)
        {

        }

        private void txtMessage_TextChanged(object sender, EventArgs e)
        {
            client.Send(lstClients.SelectedItem.ToString());
        }

        private void label3_Click(object sender, EventArgs e)
        {

        }

        private void button3_Click(object sender, EventArgs e)
        {
            try
            {
                client.Disconnect();
                btnSend.Enabled = false;
                btnConnect.Enabled = false;

            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message, "messege", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
        }

        private void vScrollBar1_Scroll(object sender, ScrollEventArgs e)
        {
            panel4.Location = new Point(panel4.Location.X,-panel4.Location.Y + -vScrollBar1.Value);
        }

        private void textBox2_TextChanged(object sender, EventArgs e)
        {

        }
    }
}