C# Socket Refusing Public Connection

Question

I am using the server and client example below to make a TCP connection via internet and in the client returns the following message:

Additional information: No connection could be made because the target machine actively refused them

The door 5902 via public IP is released, I used another software that opens a TCP connection on that same port and testing with telnet via public IP, connected normally.

Server

using System;
using System.Net.Sockets;
using System.Net;
using System.Threading;
using System.Diagnostics;

namespace Server
{
    class Server
    {
        static ManualResetEvent allDone = new ManualResetEvent(false);

        private static void ThreadInfos()
        {
            while (true)
            {
                Console.Title = "Unity C# Server - Threads: " + Process.GetCurrentProcess().Threads.Count.ToString();
                Thread.Sleep(1000);
            }
        }

        static void Main(string[] args)
        {
            //Thread to show infos on console title
            Thread thread = new Thread(new ThreadStart(ThreadInfos));
            thread.Start();

            IPEndPoint localEP = new IPEndPoint(IPAddress.Any, 5902);
            Console.WriteLine("Local address and port : {0}", localEP.ToString());

            Socket listener = new Socket(localEP.Address.AddressFamily, SocketType.Stream, ProtocolType.Tcp);

            try
            {
                listener.Bind(localEP);
                listener.Listen(10);

                while (true)
                {
                    allDone.Reset();

                    Console.WriteLine("Waiting for a connection...");
                    listener.BeginAccept(new AsyncCallback(AcceptCallback),listener);

                    allDone.WaitOne();
                }
            }
            catch (Exception e)
            {
                Console.WriteLine(e.ToString());
            }

            Console.WriteLine("Closing the listener...");
        }

        static void AcceptCallback(IAsyncResult ar)
        {
            // Get the socket that handles the client request.
            Socket listener = (Socket)ar.AsyncState;
            Socket handler = listener.EndAccept(ar);

            // Signal the main thread to continue.
            allDone.Set();

            // Create the state object.
            StateObject state = new StateObject();
            state.WorkSocket = handler;
            handler.BeginReceive(state.Buffer, 0, StateObject.BufferSize, 0, new AsyncCallback(ReadCallback), state);
        }

        public static void ReadCallback(IAsyncResult ar)
        {
            StateObject state = (StateObject)ar.AsyncState;
            Socket handler = state.WorkSocket;

            // Read data from the client socket.
            int read = handler.EndReceive(ar);

            // Data was read from the client socket.
            if (read > 0)
            {
                Console.WriteLine("[{0}] read {1} bytes", Thread.CurrentThread.ManagedThreadId, read);
                //state.sb.Append(Encoding.ASCII.GetString(state.Buffer, 0, read));
                handler.BeginReceive(state.Buffer, 0, StateObject.BufferSize, 0, new AsyncCallback(ReadCallback), state);
            }
            else
            {
                /*if (state.sb.Length > 1)
                {
                    // All the data has been read from the client;
                    // display it on the console.
                    string content = state.sb.ToString();
                    Console.WriteLine("[{0}] Read {1} bytes from socket.\n Data : {2}",
                       Thread.CurrentThread.ManagedThreadId, content.Length, content);
                }*/
                handler.Close();
            }
        }

        public class StateObject
        {
            public Socket WorkSocket = null;
            public const int BufferSize = 1024;
            public byte[] Buffer = new byte[BufferSize];
            //public StringBuilder sb = new StringBuilder();
        }
    }
}

Client

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Net.Sockets;
using System.Net;

namespace Client
{
    class Program
    {
        static void Main(string[] args)
        {
            IPHostEntry ipHostInfo = Dns.GetHostEntry(Dns.GetHostName());
            IPEndPoint remoteEP = new IPEndPoint(IPAddress.Parse("201.35.xxx.xxx"), 5902);

            Socket s = new Socket(remoteEP.Address.AddressFamily,
                SocketType.Stream, ProtocolType.Tcp);
            s.Connect(remoteEP);

            Console.WriteLine("Connected, sending a few bytes...");

            byte[] bytes = Encoding.ASCII.GetBytes("test");

            while (true)
            {
                s.Send(bytes);
            }

            s.Close();
            s.Dispose();
        }
    }
}

Answer 1

Reply given in comment: The problem was caused because the OP has a service(VNC Viewer) starting along with Windows using that same port, the port has been changed and connected in an expected way.