C#

static void Main()
{
    var listener = new TcpListener(IPAddress.Parse("127.0.0.1"), 80);
    listener.Start();


    bool serverIsOnline = true;
    while (serverIsOnline)
    {
        Console.WriteLine("Polling for a client");
        TcpClient client = listener.AcceptTcpClient();
        Console.WriteLine("Client {0} has connected", client.Client.RemoteEndPoint);

        Console.WriteLine("Handling client");
        serverIsOnline = HandleClient(client);
        Console.WriteLine("Finished handling client");

        Console.WriteLine("Closing client");
        client.Close();
    }
   listener.Stop();

}

private static bool HandleClient(TcpClient client)
{
    using(var writer = new StreamWriter(client.GetStream()))
    {
        writer.WriteLine("Welcome to the system...");
        writer.Flush();
    }
    return true;
}