multithreading - Delphi:在主线程外创建和使用套接字

Question

下面的代码旨在通过线程内的套接字读取数据。

//main method from dll
function GetSocketData(const IP, Port: PChar): PChar; export; cdecl;
var
  Thread: TMyThread;
  DataIsRead: TEvent;
begin
  DataIsRead := TEvent.Create(nil, True, False, '');
  Thread:= TMyThread.Create(DataIsRead, IP, Port);
  DataIsRead.WaitFor(INFINITE);
  Result := BlockAlloc(Thread.ResultData);
  DataIsRead.Free;
  Thread.Free;
end;

TMyThreadBase = class(TThread)
protected
  FResultData: string;
public
  constructor Create;

  property ResultData: string read FResultData;
end;

constructor TMyThreadBase.Create;
begin
  inherited Create(False); // Suspended
  FResultData := '';
  FreeOnTerminate := False;
end;

TMyThread = class(TMyThreadBase)
private
  FMyData: TMyData;
  FSocketCom: TSocketCom;
  //other params
protected
  procedure Connect(Sender: TObject);
  procedure Execute; override;
public
  constructor Create(DataIsRead: TEvent; const IP, Port: PChar);
  destructor Destroy; override;
end;

constructor TMyThread.Create(const IP, Port: PChar);
begin
  inherited Create;
  /init params/

  CoInitialize(nil);
  FSocketCom := ComCreate(FPort, FIP);
  FSocketCom.OnConnect := Connect;//Connect method sends the special command to the port {`ClientSckt.Socket.SendBuf(B[0], Count)`}
  FSocketCom.Reopen;

  FMyData := TMyData.Create(DataIsRead, FSocketCom);//class used for received data interpretation
  //DataIsRead event is being set when all data is interpreted
  FSocketCom.SetRxFunc(FMyData.NCData);//set method for data interpretation
  FMyData.InitData(...);//init values needed while data is being interpreted
end;

destructor TMyThread.Destroy;
begin
  CoUninitialize;
  inherited;
end;

procedure TMyThread.Execute;
begin
  inherited;
  while not Terminated do
    Sleep(100);
  //that is the place where I do not know what to do to wait while OnRead event is fired.
end;

TSocketCom = class(TCustomCom)
private
  ClientSckt: TClientSocket;

  procedure SocketConnect(Sender: TObject; Socket: TCustomWinSocket);
  procedure SocketRead(Sender: TObject; Socket: TCustomWinSocket);
protected
  procedure SetThread; override;
public
  constructor Create;
  destructor  Destroy; override;
  function Open:Boolean;  override;
  function Read( Buf:PAnsiChar; Size:Integer; Wait:Integer = 0 ):Integer;  override;
end;

procedure TCustomCom.SetRxFunc(OnRxData: TRxDataEvent);
begin
  ...
    SetThread;
  ...
end;

function TSocketCom.Open:boolean;
var
  i,j:integer;
begin
  ...
  ClientSckt:=TClientSocket.Create(nil);
  ClientSckt.ClientType:=ctBlocking;
  ClientSckt.HostAndAddress:='127.0.0.0';
  ClientSckt.Port:=1234;
  ClientSckt.OnConnect:=SocketConnect;
  ClientSckt.Open;
  ...
end;

function TSocketCom.Read(Buf:PAnsiChar;Size:Integer; Wait:Integer):Integer;
begin
  if Opened then
    Result:=ClientSckt.Socket.ReceiveBuf(Buf^,Size);
  if Result<0 then Result:=0;
end;

procedure TSocketCom.SetThread;
begin
  inherited;
  ClientSckt.OnRead:=SocketRead;
end;

问题: OnRead 事件没有被触发，尽管它接缝在线程中创建了所有需要的实例。建立连接并发送命令。

Answer 1

这种代码是对线程的滥用(以及对FreeOnTerminate 属性的滥用)，因为调用代码被阻塞等待线程终止，所以首先没有理由拥有线程。

话虽如此，默认情况下 TClientSocket在非阻塞模式下运行，它在内部使用窗口消息来触发套接字事件。激活套接字的线程需要有一个消息循环，以便可以正确接收和发送这些套接字通知。否则，正如马丁所说，您必须在阻塞模式下使用套接字。

更新:

您显示的更新代码在多个级别上都是完全错误的。线程全错了。 TClientSocket用法都是错的。鉴于您的 GetSocketData() 的阻塞性质函数，根本不需要在内部使用任何线程(特别是因为你说 GetSocketData() 本身是在一个线程中调用的，所以额外的线程是矫枉过正的)，而且你不应该为 TClientSocket 而烦恼。事件，尤其是 OnRead尤其是事件，因为它根本不会在阻塞模式下被调用(这是您问题的根源!)。

你让你的代码变得更复杂了。使用更像这样的东西:

function GetSocketData(const IP, Port: PChar): PChar; export; cdecl; 
var 
  ClientSckt: TClientSocket; 
  //other params 
begin 
  Result := nil;
  try
    /init params/ 

    CoInitialize(nil); 
    try
      ClientSckt := TClientSocket.Create(nil); 
      try
        ClientSckt.ClientType := ctBlocking; 
        ClientSckt.HostAndAddress := IP; 
        ClientSckt.Port := Port; 
        ClientSckt.Open; 
        try
          // send the special command to the port from here
          // read all data and interpret from here
          Result := BlockAlloc(...); 
        finally
          ClientSckt.Close;
        end;
      finally
        ClientSckt.Free;
      end;
    finally
      CoUninitialize; 
    end;
  except
  end;
end;