How to use a C# socket programming app on internet?

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C#

WinForms

networking

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I have a very simple C# client/server chat application with TCP/IP Protocol that it works on local network but I want to use it on internet network but it seem is not easily in C# and I must to do port forwarding on server router or use SSH Tunnel but I do not know How to do them?
Please help me by show me an example, a resource or a code that works....
Thank you.

What I have tried:

I just have a very simple C# client/server chat application with TCP/IP Protocol that it works on local network but I want to use it on internet network:

Server side Program:

namespace TCPIPDemo
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
 
        SimpleTcpServer server;
        private void Form1_Load(object sender, EventArgs e)
        {
            server = new SimpleTcpServer();
            server.Delimiter = 0x13;//enter
            server.StringEncoder = Encoding.UTF8;
            server.DataReceived += Server_DataReceived;
        }
 
        private void Server_DataReceived(object sender, SimpleTCP.Message e)
        {
            //Update mesage to txtStatus
            txtStatus.Invoke((MethodInvoker)delegate ()
            {
                txtStatus.Text += e.MessageString;
                e.ReplyLine(string.Format("You said: {0}", e.MessageString));
            });
        }
 
        private void btnStart_Click(object sender, EventArgs e)
        {
            //Start server host
            txtStatus.Text += "Server starting...";
            System.Net.IPAddress ip = System.Net.IPAddress.Parse(txtHost.Text);
            server.Start(ip, Convert.ToInt32(txtPort.Text));
        }
 
        private void btnStop_Click(object sender, EventArgs e)
        {
            if (server.IsStarted)
                server.Stop();
        }
    }
}

Client side Program:

namespace Client
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
 
        SimpleTcpClient client;
 
        private void btnConnect_Click(object sender, EventArgs e)
        {
            btnConnect.Enabled = false;
            //Connect to server
            client.Connect(txtHost.Text, Convert.ToInt32(txtPort.Text));
        }
 
        private void Form1_Load(object sender, EventArgs e)
        {
            client = new SimpleTcpClient();
            client.StringEncoder = Encoding.UTF8;
            client.DataReceived += Client_DataReceived;
        }
 
        private void Client_DataReceived(object sender, SimpleTCP.Message e)
        {
            //Update message to txtStatus
            txtStatus.Invoke((MethodInvoker)delegate ()
            {
                txtStatus.Text += e.MessageString;               
            });
        }
 
        private void btnSend_Click(object sender, EventArgs e)
        {
            client.WriteLineAndGetReply(txtMessage.Text, TimeSpan.FromSeconds(3));
        }
    }
}