C#

public void download(string remFileName, string locFileName)
{
    if (!logined)
    {
        login();
    }

    setBinaryMode(true);
    Console.WriteLine("Downloading file " + remFileName + " from " + remoteHost + "/" + remotePath);

    if (locFileName.Equals(""))
    {
        locFileName = remFileName;
    }

    if (!File.Exists(locFileName))
    {
        Stream st = File.Create(locFileName);
        st.Close();
    }

    FileStream output = new FileStream(locFileName, FileMode.Open);

    createDataSocket(true);
    if (dataSocket != null)
    {
        throw new SocketException();
    }
    //****
    sendCommand("RETR " + remFileName);

    if (!(retValue == 150 || retValue == 125))
    {
        throw new IOException(reply.Substring(4));
    }
    //****

    dataSocket = listeningSocket.Accept();
    listeningSocket.Close();
    listeningSocket = null;
    if (dataSocket == null)
    {
        throw new Exception("Winsock error: " +
                Convert.ToString(System.Runtime.InteropServices.Marshal.GetLastWin32Error()));
    }

    while (true)
    {
        bytes = dataSocket.Receive(buffer, buffer.Length, 0);
        output.Write(buffer, 0, bytes);

        if (bytes <= 0)
        {
            break;
        }
    }

    output.Close();

    if (dataSocket.Connected)
    {
        //dataSocket.Shutdown(SocketShutdown.Both);
        dataSocket.Close();
        dataSocket = null;
    }

    Console.WriteLine("");

    readReply();

    if (!(retValue == 226 || retValue == 250))
    {
        throw new IOException(reply.Substring(4));
    }
}

public void createDataSocket(bool flag)
{
    try
    {
        listeningSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
    }
    catch (Exception e)
    {
        ftpLog(e.Message);
        throw new IOException(e.Message);
    }

    string localAddress = clientSocket.LocalEndPoint.ToString();
    int ix = localAddress.IndexOf(':');
    if (ix < 0)
        throw new Exception("local IP ERROR");

    string localIP = localAddress.Substring(0, ix);
    IPEndPoint localEP = new IPEndPoint(IPAddress.Parse(localIP), localDataPort);

    try
    {
        //listeningSocket.SetSocketOption(SocketOptionLevel.Tcp, SocketOptionName.ReuseAddress, false);
        <big>listeningSocket.Bind(localEP);//second execution of this line causes the exception</big>
        listeningSocket.Listen(1);
    }
    catch (SocketException se)
    {
        ftpLog(se.Message);
        throw new IOException(se.Message);
    }

    localIP = localIP.Replace('.', ',');
    string portCMD = string.Format("PORT {0},{1},{2}", localIP, localDataPort / 256, localDataPort % 256);

    localDataPort++;

    sendCommand(portCMD);
    if(retValue!=200)
        throw new IOException(reply.Substring(4));
}

Discl Level	Level 1	    Level 2
1	        378600	
2		            350000
2		            28600
1	        50000	
2		            50000