Send and Receive text using sockets in Delphi 2010

Question

I do not have much familiarity with Delphi 2010 and am having trouble with using components ClientSocket and ServerSocket. The question is simple: I am trying to send a text from a client to a server using the following code:

cliente.Socket.SendText('call');

On the server side I writed the following code:

procedure TForm6.ServerClientRead(Sender: TObject; Socket: TCustomWinSocket);
var
s: string;
begin
s:=Socket.ReceiveText;
if s = 'call' then
begin
showmessage('Client is Calling');
end;
end;

However, the server dont displaying the message. Could help me once more?

Remy Lebeau · Accepted Answer · 2013-06-10 16:28:59Z

4

In D2009+, SendText() and ReceiveText() do not work correctly with Unicode strings. It is better to use SendBuf() and ReceiveBuf() directly instead.

With that said, TClientSocket and TServerSocket have been deprecated for a LONG time. You should use a different component set, such as Indy (which also ships with Delphi), eg:

IdTCPClient1.IOHandler.WriteLn('call');

procedure TForm6.IdTCPServer1Execute(AContext: TIdContext);
var
  s: string;
begin
  s := AContext.Connection.IOHandler.ReadLn;
  if s = 'call' then
  begin
    // TIdTCPServer is a multi-threaded component,
    // but ShowMessage() is not thread-safe...
    Windows.MessageBox(0, 'Client is Calling', '', MB_OK);
  end;
end;

answered Jun 10, 2013 at 16:28

Remy Lebeau

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4 Comments

V.Salles Over a year ago

It's really, the sockets are deprecated for a long time, but I did not know how to use another component to the same result, but now I know. Thank you.

V.Salles Over a year ago

Anyway for those who are still using the sokets in Delphi 2010 a function that responds to the initial question:

function ReturnStringReceive(Socket: TCustomWinSocket): String; Var Res: AnsiString; Begin SetLength(res, Socket.ReceiveBuf(Pointer(nil)^, -1)); SetLength(res, Socket.ReceiveBuf(Pointer(res)^, Length(res))); Result := String(res); End;

and to call:

procedure TForm9.ServerSocket1ClientRead(Sender: TObject;   Socket: TCustomWinSocket); begin label1.caption := ReturnStringReceive(Socket); end;

Remy Lebeau Over a year ago

@V.Salles: that is not a true solution, because it does not take message boundaries into account. Imagine what would happen if you called SendText() multiple times before ReturnStringReceive() is called. ReceiveBuf(nil, -1) (which is the same as ReceiveLength()) is likely to return a value that includes data from more than one SendText().

Remy Lebeau Over a year ago

@V.Salles: the correct way to handle this is to either: 1) preceed each string with its length, so the receiver can read the length first and then read the data, or 2) delimit the messages with a unique identifier not found in the string data, so the receiver can keep reading until it finds the delimiter.

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