Sending Byte List

[rlebeau]

I get memory error I try few scenarios with write but same error is here :-(

You need to keep the TIdTCPServer.Contexts list locked while you iterate through it, otherwise clients are free to (dis)connect from/to the server, modifying the contents of the list, while you are accessing it.

Is there some solution to send bytes, because another site is hardware with firmware who need array of bytes in TCP connection.

To send a byte array, use the TIdIOHandler.Write(TIdBytes) method instead of the TIdIOHandler.WriteLn(string) method.  Also, TIdIOHandler.WriteLn() is subject to charset encoding, so you are going to corrupt your bytes sending them as a string anyway.

Try this:

Code:

procedure TFServer.btnSendClick(Sender: TObject);
var
 bytes: TIdBytes;
 tmpList: TList;
 contexClient: TIdContext;
 i: Integer;
begin
 SetLength(bytes, 3);
 bytes[0] := $ea;
 bytes[1] := $89;
 bytes[2] := $ef;

 tmpList := IdTCPServer.Contexts.LockList;
 try
   for i := 0 to tmpList.Count-1 do
   begin
     contexClient := TIdContext(tmpList[i]);
     if contexClient <> nil then
     try
       contexClient.Connection.IOHandler.Write(bytes);
     except
     end;
   end;
 finally
   IdTCPServer.Contexts.UnlockList;
 end;
end;

That being said, if your TIdTCPServer.OnExecute event handler also sends any data to clients, then this approach becomes very dangerous, as you risk inter-mixing your bytes with other data that OnExecute may send, corrupting your communications.  In which case, the safer approach is to delegate the sending of the bytes to the OnExecute event handler, and let it decide when it is safe to send the bytes.  For example:

Code:

procedure TFServer.bIdTCPServerConnect(AContext: TIdContext);
begin
 AContext.Data := TIdThreadSafeList.Create;
end;

procedure TFServer.IdTCPServerDisconnect(AContext: TIdContext);
var
 Data: TIdThreadSafeList;
 tmpList: TList;
 i: Integer;
 P: Pointer;
begin
 Data := TIdThreadSafeList(AContext.Data);
 AContext.Data := nil;
 try
   tmpList := Data.LockList;
   try
     for i := 0 to tmpList.Count-1 do
     begin
       P := tmpList[i];
       TIdBytes(P) := nil;
     end;
   finally
     Data.UnlockList;
   end;
 finally
   Data.Free;
 end;
end;

procedure TFServer.bIdTCPServerExecute(AContext: TIdContext);
var
 Data: TIdThreadSafeList;
 tmpList: TList;
 bytes: TIdBytes;
begin
 ...
 Data := TIdThreadSafeList(AContext.Data);
 tmpList := Data.LockList;
 try
   while tmpList.Count > 0 do
   begin
     bytes := TIdBytes(tmpList[0]);
     tmpList.Delete(0);
     AContext.Connection.IOHandler.Write(bytes);
     bytes := nil;
   end;
 finally
   Data.UnlockList;
 end;
 ...
end;

procedure TFServer.btnSendClick(Sender: TObject);
var
 tmpList: TList;
 contexClient: TidContext;
 i: integer;
 bytes: TIdBytes;
begin
 tmpList := IdTCPServer.Contexts.LockList;
 try
   for i := 0 to tmpList.Count-1 do
   begin
     contexClient := TIdContext(tmpList[i]);
     if (contexClient <> nil) and (contexClient.Data <> nil) then
     begin
       SetLength(bytes, 3);
       bytes[0] := $ea;
       bytes[1] := $89;
       bytes[2] := $ef;
       TIdThreadSafeList(contexClient.Data).Add(Pointer(bytes));
       Pointer(bytes) := nil;
     end;
   end;
 finally
   IdTCPServer.Contexts.UnlockList;
 end;
end;