Binaryreader Readint32() returns too big value or -ve value

Question

I am working on client server application where server sends screen image to client using UDT ptotocol. below is my code server sends image using binary-writer and client receive data using binary-writer. Code works perfectly up to few iteration but after few iteration reader.ReadInt32() read number which is either too big or either negative. i have read most of the binary-reader related issue but not found any helpful.

Server Code:

public void SendImage(Bitmap bmp)
{
   BinaryWriter writer = new BinaryWriter(CStream);
       
   using (MemoryStream ms=new MemoryStream())
   {
       bmp.Save(ms, ImageFormat.Jpeg);//save to memory stream 

       long fileSize = ms.Length;
       writer.Write(fileSize); //send length
         
       byte[] buffer = new byte[512 * 1024];
       long pos = 0;
       ms.Seek(0, SeekOrigin.Begin);

       while (pos < fileSize)
       {
            //If buffer size is smaller then filesize then send in parts
            Int32 toSend = buffer.Length < (fileSize - pos)? buffer.Length: (Int32)(fileSize - pos);
            ms.Read(buffer, 0, toSend); //read from memory stream to byte array
            writer.Write(toSend); 
            ServerSocket.Send(buffer, 0, toSend);
            pos += toSend;

             Console.WriteLine(itration + ", fileSize : "+ fileSize + "," + toSend + ",[buffer]: " + buffer[toSend - 3] + "," + buffer[toSend - 2] + ", " + buffer[toSend-1]);
               
       }
       itration++;
           
       ms.Flush();
       ms.Close();
          }
}

Client Side Code:

private void startRead()
{
  while (true)
  {
    Bitmap inImage = ReceiveImage(Settings.Encrypted);//BitmapFromStream(Settings.Encrypted);
    theImage.Image = (Image)inImage;
  }
}
private Bitmap ReceiveImage(bool Encrypted)
{
            Bitmap img = null;
            byte[] buffer;
            BinaryReader reader = new BinaryReader(CStream);
            using(MemoryStream ms=new MemoryStream())
            {
                try
                {
                    long size = reader.ReadInt64();//read file length first

                    buffer = new byte[4 * 1024 * 1024];

                    long read = 0;

                    while (read < size)
                    {
                        int toRecv = reader.ReadInt32(); //here reader reads wrong value

                        Console.WriteLine(itration + "filesize " + size + " Byte to read : " + toRecv);

                        ReadFragment(reader, toRecv, buffer);

                        ms.Write(buffer, 0, toRecv);

                        read += toRecv;
                    }
                    itration++;
                    ms.Position = 0;
                    img = new Bitmap(ms);
                }
                catch (Exception Ex)
                {
                    Console.WriteLine(Ex.Message + " : " + Ex.StackTrace);
                }
                buffer = null;
                ms.Flush();
                ms.Close();
            }
            reader = null;
            return img;
}
private int ReadFragment(BinaryReader reader, int size, byte[] buffer)
{
       int read = 0;
       while (read < size)
       {
           read += reader.Read(buffer, read, size - read);
       }
    return read;
}

this is console output from server

0, fileSize : 568633,524288,[buffer]: 0,162, 138
0, fileSize : 568633,44345,[buffer]: 31,255, 217
1, fileSize : 568468,524288,[buffer]: 2,138, 40
1, fileSize : 568468,44180,[buffer]: 3,255, 217
2, fileSize : 578806,524288,[buffer]: 198,177, 106
2, fileSize : 578806,54518,[buffer]: 1,255, 217
3, fileSize : 589967,524288,[buffer]: 20,81, 64
3, fileSize : 589967,65679,[buffer]: 15,255, 217

11, fileSize : 632653,524288,[buffer]: 243,255, 0
11, fileSize : 632653,108365,[buffer]: 0,255, 217
12, fileSize : 642562,524288,[buffer]: 205,20, 85
12, fileSize : 642562,118274,[buffer]: 7,255, 217
13, fileSize : 645552,524288,[buffer]: 236,49, 131
13, fileSize : 645552,121264,[buffer]: 0,255, 217

and colsole output from client

0  filesize 568633 Byte to read : 524288
0  filesize 568633 Byte to read : 44345
1  filesize 568468 Byte to read : 524288
1  filesize 568468 Byte to read : 44180
2  filesize 578806 Byte to read : 524288
2  filesize 578806 Byte to read : 54518
3  filesize 589967 Byte to read : 524288
3  filesize 589967 Byte to read : 65679

11  filesize 632653 Byte to read : 524288
11  filesize 632653 Byte to read : 108365
12  filesize 642562 Byte to read : 524288
12  filesize 642562 Byte to read : 118274
13  filesize 645552 Byte to read : 524288
13  filesize 645552 Byte to read : 671776930 <-- here it read either too big number or negative number
Exception thrown: 'System.ArgumentException' in mscorlib.dll

I have tried binaryformater, protobuf instead of binaryreader but it still stops after few itration.help me find the cause.