tcp - Indy TCP - 循环读取数据

Question

TCP 服务器每 8 毫秒连续发送一次数据帧。我想编写一个能够接收这些数据帧的客户端。 Indy 9 中是否有任何程序可以知道缓冲区中是否有可用数据？

我当前的程序如下(我正在使用线程):

procedure TThreadRead.Execute;
var
  buffer: array [0..755] of byte;
  //s1: string;
  //i: integer;
begin
  IdTCPClient1.RecvBufferSize:= 756;
  IdTCPClient1.Connect;
  while Terminated = false do
  begin
    if IdTCPClient1.InputBuffer.Size = 0 then
       IdTCPClient1.ReadFromStack(True,0,False);
    while IdTCPClient1.InputBuffer.Size > 0 do
    begin
       ReadBuffer(buffer, FClient.InputBuffer.Size);
       //s1:= '';
       //For i:=0 To Length(buffer)-1 Do
       //  s1:=s1+IntToHex(Ord(buffer[i]),2); //Read values-->global var
       //Form1.Memo1.Text:=s1;
    end;
  end;
end;

有没有更高效的连续读取TCP数据的方案(比如UDP中的onread事件)？

提前致谢。

Answer 1

TIdTCPClient 不是异步组件。它不会告诉您数据何时到达。您需要使用 Timer 或 Thread 定期轮询套接字以获取新数据(TIdUDPServer 使用内部线程来触发其 OnUDPRead 事件)，例如:

procedure TForm1.Button1Click(Sender: TObject);
begin
  IdTCPClient1.Connect;
  Timer1.Enabled := True;
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
  Timer1.Enabled := False;
  IdTCPClient1.Disconnect;
end;

procedure TForm1.Timer1Timer(Sender: TObject);
var
  s1: string;
begin
  s1 := IdTCPClient1.CurrentReadBuffer;
  ...
end;

话虽如此，CurrentReadBuffer() 通常不是最好的选择。通常你会做更像这样的事情:

procedure TForm1.Timer1Timer(Sender: TObject);
begin
  Timer1.Enabled := False;

  IdTCPClient1.ReadFromStack(True, 0, False);

  while IdTCPClient1.InputBuffer.Size > 0 do
  begin
    // read one complete frame and process as needed ...
  end;

  Timer1.Enabled := True;
end;

更新:鉴于有关框架结构的新信息和您切换到线程，您应该改为这样做:

procedure TThreadRead.Execute;
var
  buffer: array of Byte;
  numbytes: Integer;
begin
  SetLength(buffer, 0);
  IdTCPClient1.Connect;
  try
    while not Terminated do
    begin
      numbytes := StrToInt('$' + IdTCPClient1.ReadString(8)) - 8;
      if numbytes <> Length(buffer) then
        SetLength(buffer, numbytes);
      if numbytes > 0 then
        IdTCPClient1.ReadBuffer(buffer[0], numbytes);
      // process buffer up to numbytes as needed...
    end;
  finally
    IdTCPClient1.Disconnect;
  end;
end;