C# - Eine vorhandene Verbindung wurde zwangsweise geschlossen durch remote-host: socket-Programmierung

Ich arbeite mit sockets. Hier sind meine codes (die Beschreibung des Problems ist weiter):

Client-Seite:

    public void ReadCallback(IAsyncResult ar)
    {
        int fileNameLen = 1;
        String content = String.Empty;
        StateObject state = (StateObject)ar.AsyncState;
        Socket handler = state.workSocket;

        int bytesRead = handler.EndReceive(ar);
        if (bytesRead > 0)
        {

            if (flag == 0)
            {

                fileNameLen = BitConverter.ToInt32(state.buffer, 0);
                string fileName = Encoding.UTF8.GetString(state.buffer, 4, fileNameLen);
                receivedPath = mypath + @"XML\";
                if (!Directory.Exists(receivedPath))
                {
                    Directory.CreateDirectory(receivedPath);
                }
                receivedPath = receivedPath + fileName;
                flag++;

            }
            if (flag >= 1)
            {

                BinaryWriter writer = new BinaryWriter(File.Open(receivedPath, FileMode.Append));
                if (flag == 1)
                {
                    writer.Write(state.buffer, 4 + fileNameLen, bytesRead - (4 + fileNameLen));
                    flag++;
                }
                else
                    writer.Write(state.buffer, 0, bytesRead);
                writer.Close();
                handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,
                new AsyncCallback(ReadCallback), state);
            }

        }
        else
        {
            //  Invoke(new MyDelegate(LabelWriter));
        }
    }

Ich bekomme Fehler auf dieser Linie: int bytesRead = handler.EndReceive(ar);

Wie kann ich diesen Fehler vermeiden?: An existing connection was forcibly closed by the remote host

Server-Seite:

        public void ReadCallback(IAsyncResult ar)
        {
            try
            {

                int fileNameLen = 1;
                String content = String.Empty;
                StateObject state = (StateObject)ar.AsyncState;
                Socket handler = state.workSocket;
                string[] str = new string[2];
                str = handler.RemoteEndPoint.ToString().Split(':');
                IP = str[0].ToString();
                int bytesRead = handler.EndReceive(ar);

                if (bytesRead > 0)
                {
                    if (flag == 0)
                    {
                        fileNameLen = BitConverter.ToInt32(state.buffer, 0);
                        string fileName = Encoding.UTF8.GetString(state.buffer, 4, fileNameLen);
                        string[] getIP = new string[3];
                        getIP = fileName.Split('_');
                        #region Send Files in HandHeld
                        #region GetLoginFile
                        if (getIP[1].ToString().Equals("GetLoginFile"))
                        {
                            string getDirectory = @"Send_Hand_Held_Files\" + DateTime.Today.ToString("dd-MM-yyyy") + "\\" + getIP[0].ToString() + "\\XML";
                            string strmyFile = getDirectory + "\\Login.xml";
                            char[] delimiter = splitter.ToCharArray();
                            split = strmyFile.Split(delimiter);
                            int limit = split.Length;
                            fName = split[limit - 1].ToString();

                            byte[] LoginfileName = Encoding.UTF8.GetBytes(fName); //file name

                            byte[] fileData = File.ReadAllBytes(strmyFile);

                            byte[] LoginfileNameLen = BitConverter.GetBytes(LoginfileName.Length); //lenght of file name
                            clientData = new byte[4 + LoginfileName.Length + fileData.Length];

                            LoginfileNameLen.CopyTo(clientData, 0);
                            LoginfileName.CopyTo(clientData, 4);
                            fileData.CopyTo(clientData, 4 + LoginfileName.Length);

                            handler.BeginSend(clientData, 0, clientData.Length, 0, new AsyncCallback(SendCallBack), handler);
                            //handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,
                            //new AsyncCallback(ReadCallback), state);
                            return;
                        }
 }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);

            }
            //SendData(IP);
        }

     private static void SendCallBack(IAsyncResult ar)
        {
            try
            {
                //Retrieve the socket from the state object.
                Socket client = (Socket)ar.AsyncState;

                //Complete sending the data to the remote device.
               //int bytesSent = client.EndSend(ar);
                //Console.WriteLine("Sent {0} bytes to server.", bytesSent);

                //Signal that all bytes have been sent.
                allDone.Set();

            }
            catch (Exception e)
            {
                Console.WriteLine(e.ToString());
            }
        }