Question

I have a client server application in which the server and the client need to send and receive objects of a custom class over the network. I am using TcpClient class for transmitting the data. I am serializing the object at the sender side and sending the resulting stream of bytes to the receiver. But at the receiver, when I try to de-serialize the bytes received, it throws Serialization Exception and the details are :

The input stream is not a valid
binary format. The starting contents
(in bytes) are:
0D-0A-00-01-00-00-00-FF-FF-FF-FF-01-00-00-00-00-00
…

My server code that serializes the object is:

byte[] userDataBytes;
MemoryStream ms = new MemoryStream();
BinaryFormatter bf1 = new BinaryFormatter();
bf1.Serialize(ms, new DataMessage());
userDataBytes = ms.ToArray();
netStream.Write(userDataBytes, 0, userDataBytes.Length);

The client code that de-serializes it is:

readNetStream.Read(readMsgBytes, 0, (int)tcpServer.ReceiveBufferSize);
MemoryStream ms = new MemoryStream(readMsgBytes);
BinaryFormatter bf1 = new BinaryFormatter();
ms.Position = 0;
object rawObj = bf1.Deserialize(ms);
DataMessage msgObj = (DataMessage)rawObj;

Please help me to solve this problem and possibly suggest any other method to transmit objects of custom classes across network using TcpClient in C#.

Thanks,
Rakesh.

Answer 1

When receiving on client side you do not know how much data you want to read.
You are only relying on the ReceiveBufferSize, while your data can be larger
or smaller then that.

I think the best approach here is to send 4 bytes that tells your client about the length of incoming data:

byte[] userDataLen = BitConverter.GetBytes((Int32)userDataBytes.Length);
netStream.Write(userDataLen, 0, 4);
netStream.Write(userDataBytes, 0, userDataBytes.Length);

and on the recieving end you first read the data length and then read
exact amount of data.

byte[] readMsgLen = new byte[4];
readNetStream.Read(readMsgLen, 0, 4);

int dataLen = BitConverter.ToInt32(readMsgLen);
byte[] readMsgData = new byte[dataLen];
readNetStream.Read(readMsgData, 0, dataLen);

Infact, I just realized, that you might has to do a little more to assure you read all data (just an idea because I haven’t tried it, but just incase you run into problem again you can try this).

The NetworkStream.Read() method returns a number indicating the amount of data it has read. It might be possible that the incoming data is larger then the RecieveBuffer. In that case you have to loop until you read all of the data. You have to do something like this:

SafeRead(byte[] userData, int len)
{
    int dataRead = 0;
    do
    {       
        dataRead += readNetStream.Read(readMsgData, dataRead, len - dataRead);

    } while(dataRead < len);
}