Send Data from [Python Client] to [C# Server] using Socket

I want to send byte data from Python-Client to C# Server using a simple Socket Application. The C# Server is working fine with a C# Client !

But when I try to use Python Socket to send data to the C#-Server, the data never arrives.

I'm not very used to Python, can someone check my Code and give me a hint how to receive the data in my c# Server?

Did I make a mistake in code? Is this maybe the wrong way to send byte data from Python to C#? Is there a better solution?

Python Client:

import socket

TCP_IP = '127.0.0.1'
TCP_PORT = 5005
MESSAGE = b'Hello World !'

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((TCP_IP, TCP_PORT))
s.send(MESSAGE)
s.close()

C# Server:

private void start()
{
    Console.WriteLine("Port: ");
    _port = Console.ReadLine();
    byte[] buffer = new Byte[1024];
    IPEndPoint localEndPoint = new IPEndPoint(IPAddress.Parse("127.0.0.1"), int.Parse(_port));
    Socket listener = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);

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

        while (true)
        {
            Console.WriteLine("Waiting for a connection...");
            Socket socket = listener.Accept();
            data = null;

            while (true)
            {
                int bytesRec = socket.Receive(buffer);
                data += Encoding.ASCII.GetString(buffer, 0, bytesRec);
                if (data.IndexOf("<EOF>") > -1)
                {
                    break;
                }
            }

            Console.WriteLine("Text received : {0}", data);
            byte[] msg = Encoding.ASCII.GetBytes(data);

            socket.Send(msg);
            socket.Shutdown(SocketShutdown.Both);
            socket.Close();
        }

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

    Console.WriteLine("\nPress ENTER to continue...");
    Console.Read();
}