data received different from data sent through a c sharp socket

Question

I'm trying to send a file from a client to a server, so I load the file in a byte array in the client side, and send it to the server through the send() method, but the received array is different and bigger than the array sent, I wonder if it's a protocol problem (but I'm using tcp protocol wich assure error detection ):

Client code:

IPAddress ipAddress = new IPAddress(ip);
IPEndPoint ipEnd = new IPEndPoint(ipAddress, 5656);
Socket clientSock = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);

FileStream fl = File.Open("pos.xls",FileMode.Open);
byte[] fileData = ReadFully(fl);
fl.Close();  

byte[] clientData = new byte[ fileData.Length];
fileData.CopyTo(clientData,0);

curMsg = "Connection to server ...";
clientSock.Connect(ipEnd);

curMsg = "File sending...";
clientSock.Send(clientData);

curMsg = "Disconnecting...";
clientSock.Close();
curMsg = "File transferred."; 

Server code:

curMsg = "Starting...";
sock.Listen(100);

curMsg = "Running and waiting to receive file.";
byte[] clientData = new byte[1024 * 5000];
while (true)
{
    Socket clientSock = sock.Accept();

    clientData = new byte[1024 * 5000];

    int receivedBytesLen = clientSock.Receive(clientData);
    curMsg = "Receiving data...";

    FileStream fz = writeFully(clientData);
    fz.Close();
    curMsg = "Saving file...";

Answer 1

You have defined clientData = new byte[1024 * 5000]; - and you then don't use receivedBytesLen . I can't remember whether that Receive overload will read as much as it can until EOF , or simply "some or EOF" (the latter being the Stream.Read behavior), but you must verify and use receivedBytesLen .

IMO, the approach of a fixed buffer is inherently flawed, as it doesn't cope well with oversized inputs either. Personally I would use a NetworkStream here; then your entire code becomes:

using(var fz = File.Create(path)) {
    networkStream.CopyTo(fz);
}

Another common approach here is to send the expected size as a prefix to the data; that way you can verify that you have the data you need. I personally wouldn't use this information to create a correct-sized buffer in memory though, as that still doesn't allow for epic-sized files (a Stream , however, does).