Unhandled exception of type 'System.IO.IOException' in System.dll?

Question

C++ / C#

public class ClientConnection : IClientConnection
    {
        private readonly Logger Log = Logger.Instance;

        byte[] buffer = new byte[2048];

        NetworkStream Stream { get; set; }

        public int Id { get; set; }

        public byte[] RemoteIPAddress { get; set; }

        public int RemoteUdpPort { get; set; }

        public ClientConnection(TcpClient client)
        {
            Stream = client.GetStream();
            // PROTOCOL_BASE_CONNECT_ACK
            SendPacket(new PROTOCOL_BASE_CONNECT_ACK());
            Log.Info("New connected");
            Stream.BeginRead(buffer, 0, buffer.Length, BeginRead, null);
        }

        public void BeginRead(IAsyncResult asyncResult)
        {
            int received = Stream.EndRead(asyncResult);
            Log.Info("Received = {0}", received);
            while (received >= 6)
            {
                int length = BitConverter.ToUInt16(buffer, 0) & 0x7FFF;

                byte[] temp = new byte[length + 2];
                Array.Copy(buffer, 2, temp, 0, temp.Length);
                int bits = Id % 7 + 1;
                BitShift.Unshift(temp, bits);
                byte[] opcode = new byte[] { temp[0], temp[1] };
                RecvOpcode packet = (RecvOpcode)BitConverter.ToUInt16(opcode, 0);
                Type t = Type.GetType("PiercingBlow.Login.Network.Recv." + packet.ToString());
                Log.Info("PacketId = {0} Lenght = {1}", BitConverter.ToUInt16(opcode, 0), temp.Length);
                if (t != null)
                {
                    ClientPacket clientpacket = (ClientPacket)Activator.CreateInstance(t);
                    clientpacket.Client = this;
                    clientpacket.Process(buffer);
                }
                else
                {
                    Log.Trace(temp.ToHex());
                }
                received -= length + 4;
                Array.Copy(buffer, length + 4, buffer, 0, received); // << Копируем оставшиеся данные в начало буфера
            }
            Stream.BeginRead(buffer, 0, buffer.Length, BeginRead, null);
        }

        public void SendPacket(ServerPacket packet)
        {
            packet.Client = this;
            packet.WriteImpl();
            byte[] data = packet.ToByteArray();
            byte[] lenght = BitConverter.GetBytes((short)data.Length);
            byte[] opcode = BitConverter.GetBytes(Convert.ToInt16((int)Enum.Parse(typeof(SendOpcode), packet.GetType().Name)));
            byte[] buff = new byte[data.Length + 4];
            Array.Copy(lenght, 0, buff, 0, lenght.Length);
            Array.Copy(opcode, 0, buff, 2, opcode.Length);
            Array.Copy(data, 0, buff, 4, data.Length);
            Stream.Write(buff, 0, buff.Length);
            Log.Debug("Send {0} bytes", buff.Length);
        }
    }
}

Answer 1

Everything is on the screenshot. The remote service terminated the connection.
Why he tore it is another question.
What kind of service is this, do you have access to it?