Question

I have code where I am trying to grow the byte array while receiving the data over my socket. This is erroring out.

    public bool ReceiveObject2(ref Object objRec, ref string sErrMsg)
    {
        try
        {
            byte[] buffer = new byte[1024];
            byte[] byArrAll = new byte[0];
            bool bAllBytesRead = false;

            int iRecLoop = 0;

            // grow the byte array to match the size of the object, so we can put whatever we 
            // like through the socket as long as the object serialises and is binary formatted 
            while (!bAllBytesRead)
            {
                if (m_socClient.Receive(buffer) > 0)
                {
                    byArrAll = Combine(byArrAll, buffer);
                    iRecLoop++;
                }
                else
                {
                    m_socClient.Close();
                    bAllBytesRead = true;
                }
            }

            MemoryStream ms = new MemoryStream(buffer);
            BinaryFormatter bf1 = new BinaryFormatter();
            ms.Position = 0;
            Object obj = bf1.Deserialize(ms);
            objRec = obj;

            return true;
        }
        catch (System.Runtime.Serialization.SerializationException se)
        {
            objRec = null;
            sErrMsg += "SocketClient.ReceiveObject " + "Source " + se.Source + "Error : " + se.Message;
            return false;
        }
        catch (Exception e)
        {
            objRec = null;
            sErrMsg += "SocketClient.ReceiveObject " + "Source " + e.Source + "Error : " + e.Message;
            return false;
        }
    }

    private byte[] Combine(byte[] first, byte[] second)
    {
        byte[] ret = new byte[first.Length + second.Length];
        Buffer.BlockCopy(first, 0, ret, 0, first.Length);
        Buffer.BlockCopy(second, 0, ret, first.Length, second.Length);
        return ret;
    }    

Error: mscorlibError : The input stream is not a valid binary format. The starting contents (in bytes) are: 68-61-73-43-68-61-6E-67-65-73-3D-22-69-6E-73-65-72 …

Yet when I just cheat and use a MASSIVE buffer size its fine.

        public bool ReceiveObject(ref Object objRec, ref string sErrMsg)
    {
        try
        {
            byte[] buffer = new byte[5000000];

            m_socClient.Receive(buffer);
            MemoryStream ms = new MemoryStream(buffer);
            BinaryFormatter bf1 = new BinaryFormatter();

            ms.Position = 0;
            Object obj = bf1.Deserialize(ms);
            objRec = obj;

            return true;
        }
        catch (Exception e)
        {
            objRec = null;
            sErrMsg += "SocketClient.ReceiveObject " + "Source " + e.Source + "Error : " + e.Message;
            return false;
        }
    }

This is really killing me. I don’t know why its not working. I have lifted the Combine from a suggestion on here too, so I am pretty sure this is not doing the wrong thing?

I hope someone can point out where I am going wrong

Answer 1

That Combine method is a really expensive way to grow an array, especially when MemoryStream is designed to address this; and the other replies are right: you must check the number of bytes read:

using(MemoryStream ms = new MemoryStream()) {
    int bytesRead;
    while((bytesRead = m_socClient.Receive(buffer)) > 0) {
        ms.Write(buffer, 0, bytesRead);
    }
    // access ms.ToArray() or ms.GetBuffer() as desired, or
    // set Position to 0 and read
}

Of course, you could just read directly from the stream (pass it to your reader)

Also – if your serialization is too big, you might consider alternative encoders, such as protobuf-net (although this will change the code a little). This may fix the problem with a huge object.