Ошибка: Тип Chat уже определяет член с именем "Listen" с теми же типами параметров - C#

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using System.Net.Sockets;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;
 
namespace ConsoleApplication2
{
    class Chat
    {
        private UdpClient udpclient;
        private IPAddress multicastaddress;
        private IPEndPoint remoteep;
        public void SendOpenMessage(string data);
        public void Listen();
 
        public Chat()
        {
            multicastaddress = IPAddress.Parse("239.0.0.222"); // один из зарезервированных для локальных нужд UDP адресов
            udpclient = new UdpClient();
            udpclient.JoinMulticastGroup(multicastaddress);
            remoteep = new IPEndPoint(multicastaddress, 2222);
        }
 
        public void SendMessage(string data)
        {
            Byte[] buffer = Encoding.UTF8.GetBytes(data);
 
            Byte[] encrypted = Encrypt(data);
 
            udpclient.Send(buffer, buffer.Length, remoteep);
 
            udpclient.Send(encrypted, encrypted.Length, remoteep);
        
        }
 
        public void Listen()
        {
 
            UdpClient client = new UdpClient();
 
            client.ExclusiveAddressUse = false;
            IPEndPoint localEp = new IPEndPoint(IPAddress.Any, 2222);
 
            client.Client.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true);
            client.ExclusiveAddressUse = false;
 
            client.Client.Bind(localEp);
 
            client.JoinMulticastGroup(multicastaddress);
 
            Console.WriteLine("\tListening started");
 
            string formatted_data;
 
            while (true)
            {
                Byte[] data = client.Receive(ref localEp);
                formatted_data = Decrypt(data);
                formatted_data = Encoding.UTF8.GetString(data);
                Console.WriteLine(formatted_data);
            }
        }
 
        private byte[] Encrypt(string clearText, string EncryptionKey = "123")
        {
 
            byte[] clearBytes = Encoding.UTF8.GetBytes(clearText);
            byte[] encrypted;
            using (Aes encryptor = Aes.Create())
            {
                Rfc2898DeriveBytes pdb = new Rfc2898DeriveBytes(EncryptionKey, new byte[] { 0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76 }); // еще один плюс шарпа в наличие таких вот костылей.
                encryptor.Key = pdb.GetBytes(32);
                encryptor.IV = pdb.GetBytes(16);
                using (MemoryStream ms = new MemoryStream())
                {
                    using (CryptoStream cs = new CryptoStream(ms, encryptor.CreateEncryptor(), CryptoStreamMode.Write))
                    {
                        cs.Write(clearBytes, 0, clearBytes.Length);
                        cs.Close();
                    }
                    encrypted = ms.ToArray();
                }
            }
            return encrypted;
        }
 
        private string Decrypt(byte[] cipherBytes, string EncryptionKey = "123")
        {
            string cipherText = "";
            using (Aes encryptor = Aes.Create())
            {
                Rfc2898DeriveBytes pdb = new Rfc2898DeriveBytes(EncryptionKey, new byte[] { 0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76 });
                encryptor.Key = pdb.GetBytes(32);
                encryptor.IV = pdb.GetBytes(16);
                using (MemoryStream ms = new MemoryStream())
                {
                    using (CryptoStream cs = new CryptoStream(ms, encryptor.CreateDecryptor(), CryptoStreamMode.Write))
                    {
                        cs.Write(cipherBytes, 0, cipherBytes.Length);
                        cs.Close();
                    }
                    cipherText = Encoding.UTF8.GetString(ms.ToArray());
                }
            }
            return cipherText;
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
 
namespace ConsoleApplication2
{
    class Program
    {
        static void Main(string[] args)
        {
            Chat chat = new Chat();
            Thread ListenThread = new Thread(new ThreadStart(chat.Listen));
            ListenThread.Start();
            string data = Console.ReadLine();
            chat.SendMessage(data);
        }
    }
}