[RESOLVE]  lnet Send/Recive custom type
lazarus / 38-Networking and Web Programming

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TheLastCayen · 2015-08-28 21:44

Hi,

I am using :
  Lazarus: 1.4.0
  FPC: 2.6.4
  lnet: 0.6.5
  OS: Linux

I need to send/receive a record but I am not sure if I am using the
right function. For now, I use aSocket.send() and aSocket.get().

Also, I am not too sure how to set the size in the function
aSocket.get().

Code: [Select]type
  { data }
  TData = record
    User: string;
    Message: String;
    Time: TDateTime;
  end;

....

procedure TForm1.MCWriteKeyPress(Sender: TObject; var Key: char);
var
  CDATA:TData;
begin
  if Key = #13 then
    Begin
      CData.User:=ECName.Text;
      CData.Time:=Now;
      CData.Message:=MCWrite.Text;
      Key:= #0;
      MCWrite.Clear;
      LTCPCClient.Send(CData,SizeOf(CData));
    end;       
end;

...

procedure TForm1.LTCPCServerReceive(aSocket: TLSocket);  
var
  S:TData;
begin
  If aSocket.Get(S,SizeOf(S)+1) > 0 then
    begin
      MSRead.Lines.Add(DateToStr(s.Time)+' - '+'('+S.User+')
'+S.Message);
    end;
end;    


Please, tell me if I am using the right functions and how to use them.

Thank you

+ Attachments and other options

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taazz · 2015-08-28 21:55

the record is full of dynamic fields. Try using array[255] of ansichar
instead of a string.

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Leledumbo · 2015-08-29 15:34

SizeOf will not return the correct size as you have dynamic string
field. Calculate the size manually (only you know the actual string
length), and no, you can't read it in one go. String is not a simple
contiguous character data only, it's a compiler defined type. Writing
bytes blindy on it will break the structure. Read each field
individually.

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TheLastCayen · 2015-09-11 15:00

Sorry for the late reply.

Thank you taazz and Leledumbo, the static array fixed my issue. My
code look like this now:

Code: [Select]type
  { data }
  TData = record
    User: array[0..24] of Char;
    Message: array[0..255] of Char;     
    Time: TDateTime;
  end;

....

procedure TForm1.MCWriteKeyPress(Sender: TObject; var Key: char);
var
  CDATA:TData;
begin
  if Key = #13 then
    Begin
      fillchar(CData.User,25,#0);
      fillchar(CData.Message,256,#0);  
      CData.User:=ECName.Text;
      CData.Time:=Now;
      CData.Message:=MCWrite.Text;
      Key:= #0;
      MCWrite.Clear;
      LTCPCClient.Send(CData,SizeOf(CData));
    end;       
end;

...

procedure TForm1.LTCPCServerReceive(aSocket: TLSocket);  
var
  S:TData;
begin
  fillchar(S.User,25,#0);
  fillchar(S.Message,256,#0);   
  S.Time:=Now;   
  aSocket.Get(S,SizeOf(S))
  MSRead.Lines.Add(DateToStr(s.Time)+' - '+'('+S.User+') '+S.Message);

end;