Windows – 10057 WSA Exception when SendBuf via Socket

delphiexceptionsocketswindows-socket-api

Client:

//is called when the client tries to log in
    procedure TLogin_Form.btnLoginClick(Sender: TObject);
    var LoginQuery: TQuery;
    begin
        //If socket not open, open it
        if not LoginSocket.Active then
        begin
            LoginSocket.Open;
        end;

      //create package
      LoginQuery.Login := ledtName.Text;
      LoginQuery.Passwort := ledtPasswort.Text;
      LoginQuery.IP := LoginSocket.Socket.LocalAddress;
      //send package
      LoginSocket.Socket.SendBuf(LoginQuery, SizeOf(LoginQuery));
    end;

Server:

    //This procedure is executed when I click on start server button
    procedure TServer_Form.btnStartStopClick(Sender: TObject);
    begin
        //If not open, open it
        if not ServerSocket.Active then
        begin
          btnStartStop.Caption := 'stop server'; 
          //Open ServerSocket
          ServerSocket.Open;
        end
      else
      begin
        //If Socket open, close it, but watch for active connctions.
        if ServerSocket.Socket.ActiveConnections > 0 then
          begin
            ShowMessage('Clients still logged in');
          end
        else
          begin
            //If no clients connected, close socket
            ServerSocket.Close;
          end;
      end;
    end;

    //This procedure is called to verify weather the user is logged in and to send the verification back
    procedure UserCheckExist(Login, Passwort: string);
    var LoginReply: TReply;
    begin
        begin
          //Connect to DB
          DBConnect(true);
          DM.AQ_LOGIN.Close;
          DM.AQ_LOGIN.SQL.Clear;
          //Count of BLOGINs
          DM.AQ_LOGIN.SQL.Add('select count(BLOGIN) from BENU where BLOGIN = ''' + Login + ''' AND BPW = ''' + Passwort + '''');
          DM.AQ_LOGIN.Open;
          //LoginReply.Action tells the client then what to do with the LoginReply.Value
          LoginReply.Action := 0;
          //if user unique
          if DM.AQ_LOGIN.Fields[0].AsInteger = 1 then
            begin
              //LoginReply.Value = 1 means the client is allowed to log in
              LoginReply.Value := 1;
              //THIS RETURNS THE WSA 10057 EXCEPTION of user is unique
              Server_Form.ServerSocket.Socket.SendBuf(LoginReply, SizeOf(LoginReply));
            end
          else
            begin
                //LoginReply.Value = 0 means the client is NOT allowed to log in
                LoginReply.Value := 0;

                //THIS RETURNS THE WSA 10057 EXCEPTION if user is NOT unique
                Server_Form.ServerSocket.Socket.SendBuf(LoginReply, SizeOf(LoginReply));
            end;
          //Close ADOQuery
          DM.AQ_LOGIN.Close;
          //Close DB Connection
          DBConnect(false);
        end;
    end;

    //Is called when something is in the socket connection
    procedure TServer_Form.ServerSocketClientRead(Sender: TObject;
      Socket: TCustomWinSocket);
    var Query: TQuery;
    begin
        //Reads from the Socket (cant use ServerSocket.Socket.ReceiveBuf whysoever, but this is another thread)
        Socket.ReceiveBuf(Query, SizeOf(Query));
      case Query.Action of
        //If Query.Action = 0, which means the client tries to login call UserCheckExist
        0:  UserCheckExist(Query.Login, Query.Passwort);
      //Otherwise, getfuckedup
      else ShowMessage('Query Action not defined');
      end;
    end;

One strange thing is that I have to send the login + pw from the client two times.

The first time send (Client), I get onClientConnect and onAccept at the server.
The second time i send (Client), the server executes the code until the line I marked . I get a 10057 WSA Exception.

Why do I get this error? Strange however is, that if I open the socket on the server right before the line where I get the Exception saying that 'socket not open', I get it anyways

Best Solution

The code you have shown will not work on both the client and server sides due to several bugs in your code.

When TClientSocket is set to ctNonBlocking mode (which I am assuming you are using), Open() will not trigger the OnConnect event until after btnLoginClick() has exited and flow has returned to the message queue. It is not valid to read or write data from a socket until the OnConnect event has fired. So you should move your sending code into the OnConnect event itself. You also need to take into account that SendBuf() may not be able to send all of the data in a single packet. If SendBuf() returns -1 and WSAGetLastError() returns WSAEWOULDBLOCK afterwards (which will always be true if the OnError event was not triggered), then data was not sent in its entirety. You must buffer any unsent bytes somewhere, and then wait for the OnWrite event to fire before trying to write the buffered bytes again, or anything else for the matter, to the socket.

As for your server code, you are trying to write outbound data to the wrong object. You must read and write data using the TCustomWinSocket object that the OnRead event provided. You are trying to write data to the server's TServerWinSocket object instead, which does not represent a valid socket endpoint for any connected client. You also need to look at the return value of ReceiveBuf() in order to handle partial transmissions as well.

Try something more like the following:

Common:

type
  // helper class that holds buffered input/output data
  SocketBuffers = class
  public
    constructor Create;
    destructor Destroy;
    Inbound: TMemoryStream;
    Outbound: TMemoryStream;
  end;

constructor SocketBuffers.Create;
begin
  inherited;
  Inbound := TMemoryStream.Create;
  Outbound := TMemoryStream.Create;
end;

destructor SocketBuffers.Destroy;
begin
  Inbound.Free;
  Outbound.Free;
  inherited;
end;

// removes processed bytes from a buffer
procedure CompactBuffer(Buffer: TMemoryStream);
begin
  if Buffer.Position > 0 then
  begin
    // bytes have been processed, remove them from the buffer...
    if Buffer.Position < Buffer.Size then
    begin
      // move unprocessed bytes to the front of the buffer...
      Move(Pointer(Longint(Buffer.Memory)+Buffer.Position)^, Buffer.Memory^, Buffer.Size - Buffer.Position);
      // reduce the buffer size just the remaining bytes...
      Buffer.Size := Buffer.Size - Buffer.Position;
    end else
    begin
      // all bytes have been processed, clear the buffer...
      Buffer.Clear;
    end;
  end;
end;

// sends raw bytes to the specified socket, buffering any unsent bytes
function SendDataToSocket(Socket: TCustomWinSocket; Data: Pointer; DataSize: Integer; Buffer: TMemoryStream): Integer;
var
  DataPtr: PByte;
  NumSent: Integer;
begin
  Result := 0;
  DataPtr := PByte(Data);
  if DataSize > 0 then
  begin
    if Buffer.Size = 0 then
    begin
      // the buffer is empty, send as many bytes as possible...
      repeat
        NumSent := Socket.SendBuf(DataPtr^, DataSize);
        if NumSent <= 0 then Break; // error or disconnected
        Inc(DataPtr, NumSent);
        Dec(DataSize, NumSent);
        Inc(Result, NumSent);
      until DataSize = 0;
      if DataSize = 0 then Exit; // nothing left to send or buffer
    end;
    // add unsent bytes to the end of the buffer...
    Buffer.Seek(0, soFromEnd);
    Buffer.WriteBuf(DataPtr^, DataSize);
    Inc(Result, DataSize);
  end;
end;

// sends buffered bytes to the specified socket
procedure SendBufferToSocket(Socket: TCustomWinSocket; Buffer: TMemoryStream);
var
  DataPtr: PByte;
  NumSent: Integer;
begin
  // start at the beginning of the buffer
  Buffer.Position := 0;
  DataPtr := PByte(Buffer.Memory);
  while Buffer.Position < Buffer.Size do
  begin
    NumSent := Socket.SendBuf(DataPtr^, Buffer.Size - Buffer.Position);
    if NumSent <= 0 then Break; // error or disconnected
    Inc(DataPtr, NumSent);
    Buffer.Seek(NumSent, soFromCurrent);
  end;
  // remove bytes that were sent...
  CompactBuffer(Buffer);
end;

// reads raw bytes from the specified socket ands buffers them
procedure ReadBufferFromSocket(Socket: TCustomWinSocket; Buffer: TMemoryStream);
var
  NumRecv: Integer;
  OldSize: Integer;
begin
  repeat
    NumRecv := Socket.ReceiveLength;
    if NumRecv <= 0 then Exit; // error or no data available

    // increase the size of the buffer
    OldSize := Buffer.Size;
    Buffer.Size := Buffer.Size + NumRecv;

    // read bytes into the new memory space
    NumRecv := Socket.ReceiveBuf(Pointer(Longint(Buffer.Memory)+OldSize)^, NumRecv);
    if NumRecv <= 0 then
    begin
      // nothing read, free the unused memory
      Buffer.Size := OldSize;
      Exit;
    end;
  until False;
end;

Client:

var
  Buffers: SocketBuffers = nil;

procedure TLogin_Form.FormCreate(Sender: TObject);
begin
  Buffers := SocketBuffers.Create;
end;

procedure TLogin_Form.FormDestroy(Sender: TObject);
begin
  LoginSocket.Close;
  Buffers.Free;
end;

procedure TLogin_Form.btnLoginClick(Sender: TObject);
begin
  if not LoginSocket.Active then
  begin
    Buffers.Inbound.Clear;
    Buffers.Outbound.Clear;
    LoginSocket.Open;
  end;
end;

procedure TLogin_Form.LoginSocketConnect(Sender: TObject; Socket: TCustomWinSocket);
var
  LoginQuery: TQuery;
begin
  LoginQuery.Login := ledtName.Text;
  LoginQuery.Passwort := ledtPasswort.Text;
  LoginQuery.IP := LoginSocket.Socket.LocalAddress;

  // send query, buffering unsent bytes if needed...
  SendDataToSocket(Socket, @LoginQuery, SizeOf(LoginQuery), Buffers.Outbound);
end;

procedure TLogin_Form.LoginSocketRead(Sender: TObject; Socket: TCustomWinSocket);
var
  Buffer: TmemoryStream;
  Available: Integer;
  Query: TQuery;
begin
  Buffer := Buffers.Inbound;

  // read available bytes into the buffer...
  ReadBufferFromSocket(Socket, Buffer);

  // process complete queries, ignore unfinished queries until later...
  Buffer.Position := 0;
  repeat
    Available := Buffer.Size - Buffer.Position;
    if Available < SizeOf(Query) then Break;
    Buffer.ReadBuf(Query, SizeOf(Query));
    // process query as needed ...
  until False;

  // remove processed bytes from the buffer...
  CompactBuffer(Buffer);
end;

procedure TLogin_Form.LoginSocketWrite(Sender: TObject; Socket: TCustomWinSocket);
begin
  // can send any buffered bytes now...
  SendBufferToSocket(Socket, Buffers.Outbound);
end;

Server:

procedure TServer_Form.btnStartStopClick(Sender: TObject);
begin
  if not ServerSocket.Active then
  begin
    btnStartStop.Caption := 'stop server'; 
    ServerSocket.Open;
  end
  else if ServerSocket.Socket.ActiveConnections > 0 then
  begin
    ShowMessage('Clients still logged in');
  end
  else
  begin
    ServerSocket.Close;
  end;
end;

procedure UserCheckExist(Socket: TCustomWinSocket; Login, Password: string);
var
  LoginReply: TReply;
begin
  ...
  LoginReply.Value := ...;

  // send query, buffering unsent bytes if needed...
  SendDataToSocket(Socket, @LoginReply, Sizeof(LoginReply), SocketBuffers(Socket.Data).Outbound);
  ...
end;


procedure TServer_Form.ServerSocketClientConnect(Sender: TObject; Socket: TCustomWinSocket);
begin
  Socket.Data := SocketBuffers.Create;
end;

procedure TServer_Form.ServerSocketClientDisconnect(Sender: TObject; Socket: TCustomWinSocket);
begin
  SocketBuffers(Socket.Data).Free;
  Socket.Data := nil;
end;

procedure TServer_Form.ServerSocketClientRead(Sender: TObject; Socket: TCustomWinSocket);
var
  Buffer: TmemoryStream;
  Available: Integer;
  Query: TQuery;
begin
  Buffer := SocketBuffers(Socket.Data).Inbound;

  // read available bytes into the buffer...
  ReadBufferFromSocket(Socket, Buffer);

  // process complete queries, ignore unfinished queries until later...
  Buffer.Position := 0;
  repeat
    Available := Buffer.Size - Buffer.Position;
    if Available < SizeOf(Query) then Break;
    Buffer.ReadBuf(Query, SizeOf(Query));
    // process query as needed ...
    case Query.Action of
      0: UserCheckExist(Socket, Query.Login, Query.Password);
      ...
    end;
  until False;

  // remove processed bytes from the buffer...
  CompactBuffer(Buffer);
end;

procedure TServer_Form.ServerSocketClientWrite(Sender: TObject; Socket: TCustomWinSocket);
begin
  // can send any buffered bytes now...
  SendBufferToSocket(Socket, SocketBuffers(Socket.Data).Outbound);
end;