如何在已经运行的线程中运行代码以安全地发送/接收数据 [TidTCPServer]

Question

UPDATE Problem Still Exists.

Is it possible to run code in already running thread? for example: thread1 is running some code & i want to run code from thread2 in thread1.

I want to run code in idTCPServer thread to send some data to client

Edit: After research seems that my problem is that when Client data is received or is receiving same time another thread is trying to write to that socket.

Edit:

procedure TMainFrm.UserSRVExecute(AContext: TIdContext);
var
 Command        : String;
 msSize         : Int64;
 ms             : TMemoryStream;
 decompressedMS : TMemoryStream;
 H              : TIdNotify;
begin
// Application.ProcessMessages;
 Command := AContext.Connection.Socket.ReadLn;
// messagebox(0,'snd','',$40);
 if logb then mainfrm.mconnections.Lines.Add(command + ' - BEGIN');

 if Command <> '' then   // keepalive 
  begin
  //Application.ProcessMessages;
   msSize         := AContext.Connection.Socket.ReadInt64;
   ms             := TMemoryStream.Create;
   decompressedMS := TMemoryStream.Create;
   try
    AContext.Connection.Socket.ReadStream(ms, msSize);
    ms.Position := 0;
    DecompressStream(MS,decompressedMS);
    decompressedMS.Position := 0;
    Client_ProcessData(AContext,Command,decompressedMS);
   finally
    ms.Free;
    decompressedMS.Free;
    if logb then mainfrm.mconnections.Lines.Add(command + ' - END');
   end;
  end;
end;


procedure Client_ProcessData(AContext: TIdContext; cmd : String; data : TMemoryStream);
var
 Hnd     : THandle;
 clData  : TStringArray;
 TmpStr1 : String;
 Tmp     : String;
 TN      : TIdNotify;

 Sync    : TMySync;
 I,I2    : Integer;
begin
 Hnd := AContext.Connection.Socket.Binding.Handle;

 if cmd = 'scr' then  // RECEIVE COMMAND TO SEND TO CLIENT TO RECEIVE DATA FROM CLIENT
  begin
   Tmp := StreamToString(data);
   {Sync := TMySync2.Create(True);
   try
    Sync.cmd := cmd;
    Sync.hnd := Hnd;
    Sync.tmp := TmpStr1;
    Sync.Resume;
   finally
    //Sync.Free;
   end;  }
   log('>>> CLFROMAS: '+IntToStr(HND)+':::'+cmd+':::');
 //  SendCMDToSocket(MainFrm.UserSRV,StrToInt(Trim(Tmp)),'scr'+IntToStr(Hnd));
   I2 := StrToInt(Trim(Tmp));
  for I := 0 to 100 do
  if USRVData[i].hnd = I2 then
   begin
   // cs.Acquire;
    USRVData[i].CTX.Connection.Socket.WriteLn('scr'+IntToStr(Hnd));  // PLACED ALL CONTEXTs IN GLOBAL VARIABLE + ALL SOCKET HANDLES. <--- HERE IS THE PROBLEM
   // cs.Release;
    Break;
   end;
 //  log('>>> CLFROMAS: '+IntToStr(HND)+':::'+cmd+':::'+streamtostring(data));
   Exit;
  end;

   if Copy(cmd,1,Length('scr4u')) = 'scr4u' then // RECEIVE DATA FROM CLIENT TO SEND IT TO ADMIN CLIENT REQUEST ABOVE
   begin
    if Length(cmd) > Length('scr4u') then
     begin
      Delete(cmd,1,Length('scr4u'));
      Data.Position := 0;
     { Sync := TMySync.Create;
      try
       Sync.cmd := cmd;
       Sync.hnd := Hnd;
       Sync.data := TMemoryStream.Create;
       Sync.data.CopyFrom(data,data.Size);
       Sync.data.Position := 0;
       Sync.DoNotify;
      finally
       Sync.data.Free;
       Sync.Free;
      end;  }
      SendStreamToSocket(MainFrm.UserSRV,strtoint(cmd),'scr4u',Data);

      log('>>>>> ADMIN: '+IntToStr(HND)+':::'+cmd+':::'{+streamtostring(data)});
     end else TmpStr1 := '';
    Exit;
   end;

   ...

UPDATE

procedure TMainFrm.UserSRVExecute(AContext: TIdContext);
var
 Command        : String;
 msSize         : Int64;
 ms             : TMemoryStream;
 decompressedMS : TMemoryStream;
 H              : TIdNotify;
 I              : Integer;
 List, Messages : TStringList;
begin
  Messages := nil;
  try
   List := TMyContext(AContext).OutgoingMessages.Lock;
   try
    if List.Count > 0 then
     begin
      Messages := TStringList.Create;
      Messages.Assign(List);
      List.Clear;
     end;
   finally
    TMyContext(AContext).OutgoingMessages.Unlock;
   end;
   if Messages <> nil then
    begin
     for I := 0 to Messages.Count-1 do
      begin
       AContext.Connection.IOHandler.WriteLn(Messages.Strings[I]);
      end;
    end;
  finally
   Messages.Free;
  end;

  if AContext.Connection.IOHandler.InputBufferIsEmpty then
   begin
    AContext.Connection.IOHandler.CheckForDataOnSource(100);
    AContext.Connection.IOHandler.CheckForDisconnect;
    if AContext.Connection.IOHandler.InputBufferIsEmpty then
      Exit;
   end;

 Command := AContext.Connection.Socket.ReadLn;

 if logb then mainfrm.mconnections.Lines.Add(command + ' - BEGIN');

 if Command <> '' then
  begin
   msSize         := AContext.Connection.Socket.ReadInt64;
   ms             := TMemoryStream.Create;
   decompressedMS := TMemoryStream.Create;
   try
    AContext.Connection.Socket.ReadStream(ms, msSize);
    ms.Position := 0;
    DecompressStream(MS,decompressedMS);
    decompressedMS.Position := 0;
    Client_ProcessData(AContext,Command,decompressedMS);
   finally
    ms.Free;
    decompressedMS.Free;
    if logb then mainfrm.mconnections.Lines.Add(command + ' - END');
   end;
  end;
end;

Answer 1

Is it possible to run code in already running thread? for example: thread1 is running some code & i want to run code from thread2 in thread1.

No. Thread1 needs to be explicitly coded to stop what it is currently doing, do something else, and then go back to what it was previous doing. All Thread2 can do is signal Thread1 to perform that stop+continue at its earliest convenience.

I want to run code in idTCPServer thread to send some data to client

Your TIdTCPServer.OnExecute event handler needs to check for that data periodically and send it when it is available.

You can use the TIdContext.Data property, or derive a custom class from TIdServerContext and assign it to the TIdTCPServer.ContextClass property, to provide a per-client thread-safe buffer for your outbound data. Your OnExecute handler can then access that buffer when needed.

For example:

type
  TMyContext = class(TIdServerContext)
  public
    constructor Create(AConnection: TIdTCPConnection; AYarn: TIdYarn; AList: TIdContextThreadList = nil); override;
    destructor Destroy; override;
    OutgoingMessages: TIdThreadSafeStringList;
  end;

constructor TMyContext.Create(AConnection: TIdTCPConnection; AYarn: TIdYarn; AList: TIdContextThreadList = nil);
begin
  inherited;
  OutgoingMessages := TIdThreadSafeStringList.Create;
end;

destructor TMyContext.Destroy;
begin
  OutgoingMessages.Free;
  inherited;
end;

procedure TMyForm.FormCreate(Sender: TObject);
begin
  // this must be set before activating the server...
  IdTCPServer1.ContextClass := TMyContext;
end;

procedure TMyForm.IdTCPServer1Execute(AContext: TIdContext);
var
  List, Messages: TStringList;
begin
  // check for outgoing data...

  Messages := nil;
  try
    List := TMyContext(AContext).OutgoingMessages.LockList;
    try
      if List.Count > 0 then
      begin
        Messages := TStringList.Create;
        Messages.Assign(List);
        List.Clear;
      end;
    finally
      TMyContext(AContext).OutgoingMessages.UnlockList;
    end;
    if Messages <> nil then
    begin
      // send Messages using AContext.Connection.IOHandler as needed...
    end;
  finally
    Messages.Free;
  end;

  // check for incoming data...

  if AContext.Connection.IOHandler.InputBufferIsEmpty then
  begin
    AContext.Connection.IOHandler.CheckForDataOnSource(100);
    AContext.Connection.IOHandler.CheckForDisconnect;
    if AContext.Connection.IOHandler.InputBufferIsEmpty then
      Exit;
  end;

  // process incoming data as needed...
end;

procedure TForm1.SomeProcedure;
var
  List: TIdContextList;
  Context: TMyContext;
begin
  List := IdTCPServer1.Contexts.LockList;
  try
    Context := TMyContext(List[SomeIndex]);
    Context.OutgoingMessages.Add('something');
  finally
    IdTCPServer1.Contexts.UnlockList;
  end;
end;