Socket Problem

Ich habe einen Server mit winapi geschrieben der so aussieht (teile)

while(rc!=SOCKET_ERROR)
{
   rc=recv(connectedSocket,buf,256,0);

   if(rc==0 || rc==SOCKET_ERROR)
      break;

   buf[rc]='\0';

   if(!strcmp(buf, "/test"))
      test();
}

Die test() Methode :

void test()
{
	printf("test start...\n");
	int i = send(connectedSocket,(const char*)"test",sizeof("test"),0);

	if (i == SOCKET_ERROR)
        printf("send() failed with error: %d\n", WSAGetLastError());
}

Meinen Client hab ich mit C# geschrieben

void connect()
        {
            if (textBoxIP.Text == "" || textBoxPort.Text == "")
            {
                MessageBox.Show("IP Address and Port Number are required to connect to the Server\n");
                return;
            }
            try
            {
                m_clientSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
                IPAddress ip = IPAddress.Parse(textBoxIP.Text);
                int iPortNo = System.Convert.ToInt16(textBoxPort.Text);
                IPEndPoint ipEnd = new IPEndPoint(ip, iPortNo);
                m_clientSocket.Connect(ipEnd);
                if (m_clientSocket.Connected)
                {
                    WaitForData();
                }
            }
            catch (SocketException se)
            {
                string str;
                str = "\nConnection failed, is the server running?\n" + se.Message;
                MessageBox.Show(str);
            }
        }

        public void WaitForData()
        {
            try
            {
                if (m_pfnCallBack == null)
                {
                    m_pfnCallBack = new AsyncCallback(OnDataReceived);
                }
                SocketPacket theSocPkt = new SocketPacket();
                theSocPkt.thisSocket = m_clientSocket;

                m_result = m_clientSocket.BeginReceive(theSocPkt.dataBuffer,
                                                        0, theSocPkt.dataBuffer.Length,
                                                        SocketFlags.None,
                                                        m_pfnCallBack,
                                                        theSocPkt);
                MessageBox.Show("" + theSocPkt.dataBuffer); 
            }
            catch (SocketException se)
            {
                MessageBox.Show(se.Message);
            }

        }

        public class SocketPacket
        {
            public System.Net.Sockets.Socket thisSocket;
            public byte[] dataBuffer = new byte[1024];
        }

        public void OnDataReceived(IAsyncResult asyn)
        {
            try
            {
                SocketPacket theSockId = (SocketPacket)asyn.AsyncState;
                int iRx = theSockId.thisSocket.EndReceive(asyn);
                char[] chars = new char[iRx + 1];
                System.Text.Decoder d = System.Text.Encoding.UTF8.GetDecoder();
                int charLen = d.GetChars(theSockId.dataBuffer, 0, iRx, chars, 0);
                System.String szData = new System.String(chars);
                MessageBox.Show("" + szData);
                WaitForData();
            }
            catch (ObjectDisposedException)
            {
                System.Diagnostics.Debugger.Log(0, "1", "\nOnDataReceived: Socket has been closed\n");
            }
            catch (SocketException se)
            {
                MessageBox.Show(se.Message);
            }
        }

Ein Button den ich erstellt habe macht sendMessage("/test")

void sendMessage(String message)
        {
            try
            {
                byte[] byData = System.Text.Encoding.ASCII.GetBytes(message);
                if(m_clientSocket != null){
                    m_clientSocket.Send (byData);
                }
            }
            catch (SocketException se)
            {
                MessageBox.Show(se.Message);
            }
        }

Ergebnis : "/test" kommt an ohne Problem
Problem : der Server (mit winapi geschrieben sehe oben) gibt die Fehlermeldung 10083 aus

Was kann ich da machen ?