Problem receiving file from TCP socket C #

In one part of my application I send a file from one PC to another from a TCP socket, the connection and sending the file seems to me to be perfect, there are no problems since it is very simple, here the code:

            IPEndPoint remoteEP = new IPEndPoint(ip, port);
        Socket client = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);

            connectDone.Reset();
            sendDone.Reset();

            client.BeginConnect(remoteEP, new AsyncCallback(ConnectCallback), client);
            connectDone.WaitOne();

            Controlador.PermitirEnviarArchivo.Set();

            //Envio nombre del archivo
            client.Send(Encoding.ASCII.GetBytes(Path.GetFileName(rutaArchivo) + "<KC>"));
            //recivo el ok
            client.Receive(new byte[1024]);
            //envio el archivo
            client.SendFile(rutaArchivo);

            client.Shutdown(SocketShutdown.Send);
            client.Close();

The problem I'm having when I receive it, I do not know if I'm using any index and offset wrong, I can not think of anything else to try! I show when I already established the connection

 public void ReadCallback(IAsyncResult ar)
    {
        StateObject state = (StateObject)ar.AsyncState;
        Socket handler = state.workSocket;

        int bytesRead = handler.EndReceive(ar);

        if (bytesRead > 0)
        {
            Configuracion c = new Configuracion().Leer();
            if (!state.esArchivo)//Nombre del archivo
            { 
                state.sb.Append(Encoding.ASCII.GetString(state.buffer, 0, bytesRead));
                state.nombreArchivo += state.sb.ToString();
                if (state.nombreArchivo.IndexOf("<KC>") > -1)
                {
                    state.nombreArchivo = state.nombreArchivo.Split('<')[0];
                    handler.Send(Encoding.ASCII.GetBytes("<KC>"));
                    state.esArchivo = true;
                    if (File.Exists(c.rutaDescarga + "\" +state.nombreArchivo))
                    {
                        File.Delete(c.rutaDescarga + "\" + state.nombreArchivo);
                    }
                    state.buffer = new byte[StateObject.BufferSize];
                    handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0, new AsyncCallback(ReadCallback), state);
                }
                else
                    handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,new AsyncCallback(ReadCallback), state);
            }
            else //Archivo
            {
                    using (FileStream fs = new FileStream(c.rutaDescarga + "\" +state.nombreArchivo, FileMode.Append, FileAccess.Write))
                    {
                    fs.Write(state.buffer, 0, bytesRead);
                    }
                    handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0, new AsyncCallback(ReadCallback), state);
            }
        }
    }

and my StateObject object

        public class StateObject
    {
        public string nombreArchivo = "";
        public bool esArchivo = false;
        public Socket workSocket = null;
        public const int BufferSize = 1048576;

        public byte[] buffer = new byte[BufferSize];

        public StringBuilder sb = new StringBuilder();
    }

error: I do not know what is happening, I gave up trying: c

Thank you!