Question

To put my toe in the water of Network programming, I wrote a little Console App to send a png file to a server (another console app). The file being written by the server is slightly bigger than the source png file. And it will not open.

The code for the client app is:

    private static void SendFile()
    {
        using (TcpClient tcpClient = new TcpClient("localhost", 6576))
        {
            using (NetworkStream networkStream = tcpClient.GetStream())
            {
                //FileStream fileStream = File.Open(@"E:\carry on baggage.PNG", FileMode.Open);

                byte[] dataToSend = File.ReadAllBytes(@"E:\carry on baggage.PNG");

                networkStream.Write(dataToSend, 0, dataToSend.Length);
                networkStream.Flush();

            }
        }

    }

The code for the Server app is :

    private static void Main(string[] args)
    {
        Thread thread = new Thread(new ThreadStart(Listen));
        thread.Start();

        Console.WriteLine("Listening...");
        Console.ReadLine();
    }

    private static void Listen()
    {
        IPAddress localAddress = IPAddress.Parse("127.0.0.1");
        int port = 6576;
        TcpListener tcpListener = new TcpListener(localAddress, port);
        tcpListener.Start();

        using (TcpClient tcpClient = tcpListener.AcceptTcpClient())
        {
            using (NetworkStream networkStream = tcpClient.GetStream())
            {
                using (Stream stream = new FileStream(@"D:\carry on baggage.PNG", FileMode.Create, FileAccess.ReadWrite))
                {
                    // Buffer for reading data
                    Byte[] bytes = new Byte[1024];
                    var data = new List<byte>();

                    int length;

                    while ((length = networkStream.Read(bytes, 0, bytes.Length)) != 0)
                    {
                        var copy = new byte[length];
                        Array.Copy(bytes, 0, copy, 0, length);
                        data.AddRange(copy);
                    }

                    BinaryFormatter binaryFormatter = new BinaryFormatter();
                    stream.Position = 0;
                    binaryFormatter.Serialize(stream, data.ToArray());
                }
            }

        }
        tcpListener.Stop();

The size of the written file is 24,103Kb, whereas the source file is only 24,079Kb.

Is it apparent to anyone why this operation is failing?

Cheers

Answer 1

You are writing your output using a BinaryFormatter. I’m pretty sure that this will add some bytes at the start of the output to indicate the type that you’re outputting (in this case System.Byte[]).
Just write the bytes out directly to the file without using the formatter:

using (Stream stream = new FileStream(@"D:\carry on baggage.PNG", FileMode.Create, FileAccess.ReadWrite))
{
    // Buffer for reading data
    Byte[] bytes = new Byte[1024];

    int length;

    while ((length = networkStream.Read(bytes, 0, bytes.Length)) != 0)
    {
        stream.Write(bytes, 0, length);
    }
}