multithreading - 尝试通过 tcp/ip 发送文件时表单卡住，Delphi 2010

Question

我面临以下问题。我和我的一个 friend 使用超高频数据调制解调器建立了无线网络。当我尝试发送文件(例如照片)并且连接正常时没有问题。但是，当我尝试发送文件并且由于某种原因有一段时间没有连接时，表单会卡住，直到重新建立。有人可以帮我吗？这是我在服务器端和客户端使用的代码(Delphi 2010)。

客户端(传输文件[如果连接暂时或永久丢失，此表单将卡住]):

procedure TForm17.BtnSendFile(Sender: TObject);
var
 FS: TFileStream;
 filename: string;
begin 
 filetotx := 'temp.jpg';  
 FS := TFileStream.Create(filetotx, fmOpenRead, fmShareDenyWrite);
 FS.Position := 0;
  try
   Form1.IdTCPClient1.Socket.LargeStream := true;
   Form1.IdTCPClient1.Socket.WriteLn('PIC');
   Form1.IdTCPClient1.Socket.Write(FS, 0, true);
  finally
   FS.Free;
  end;
end;

服务器端(接收文件)

procedure TForm1.IdTCPServer1Execute(AContext: TIdContext);
var
s, filename:string;
FS: TFileStream;
Jpg: TJpegImage;
begin
S := AContext.Connection.Socket.ReadLn;
if S = 'PIC' then
 begin
  filename := 'PIC_' + datetostr(date) + ' ' + timetostr(time) + '.jpg';
  filename := StringReplace(filename, '/', '-', [rfReplaceAll]);
  filename := StringReplace(filename, ':', '_', [rfReplaceAll]);
  filename := extractfilepath(Application.exename) + 'PIC\' + filename;
  FS := TFileStream.Create(filename, fmCreate);
  FS.Position := 0;
  AContext.Connection.Socket.LargeStream := true;
  AContext.Connection.Socket.ReadStream(FS);
  Jpg := TJpegImage.Create;
  FS.Position := 0;
  Jpg.LoadFromStream(FS);
  form26.image1.Picture.Assign(Jpg);
  try
   Jpg.Free;
   FS.Free;       
  finally
    //send feedback file received
   AContext.Connection.Socket.WriteLn('PICOK');
   TIdNotify.NotifyMethod(form26.Show);
  end;
end;

客户端(接收反馈“PICOK”)

type
  TReadingThread = class(TThread)
  protected
    FConn: TIdTCPConnection;
    procedure Execute; override;
    procedure DoTerminate; override;
  public
    constructor Create(AConn: TIdTCPConnection); reintroduce;
  end;

constructor TReadingThread.Create(AConn: TIdTCPConnection);
begin
 TLog.AddMsg('Client Thread Created');
 FConn := AConn;
 inherited Create(False);
end;


procedure TReadingThread.Execute;
begin
 while not Terminated do
  begin
  if S='MSGOK' then
  .
  .
  else if S = 'PICOK' then
  begin
   Do Something
  end
  end;
 end;

procedure TReadingThread.DoTerminate;
begin
 TLog.AddMsg('Disconnected'); 
 inherited;
end;

Answer 1

您的客户端代码正在主 UI 线程的上下文中发送文件。这就是 UI 卡住的原因 - 发送繁忙时没有消息正在处理。要么将该代码移动到工作线程中(首选)，要么将 TIdAntiFreeze 组件拖放到您的表单上。

就实际文件传输而言，您的服务器代码没有问题，但是您的 try/finally block 是错误的，并且您直接访问 TImage 而不进行同步与主 UI 线程。您在调用 form26.Show 时已经进行了同步，只需在调用 form26.image1.Picture.Assign(Jpg) 时也进行同步即可。试试这个:

procedure TForm1.IdTCPServer1Execute(AContext: TIdContext);
var
  S, Filename: string;
  FS: TFileStream;
  Jpg: TJpegImage;
begin
  S := AContext.Connection.Socket.ReadLn;
  if S = 'PIC' then
  begin
    Filename := ExtractFilePath(Application.ExeName) + 'PIC\' + FormatDateTime('"PIC_"mm"-"dd"-"yyyy" "hh"_"nn"_"ss".jpg"', Now);
    FS := TFileStream.Create(Filename, fmCreate);
    try
      AContext.Connection.Socket.LargeStream := true;
      AContext.Connection.Socket.ReadStream(FS);
      FS.Position := 0;
      Jpg := TJpegImage.Create;
      try
        Jpg.LoadFromStream(FS);
        TThread.Synchronize(nil,
          procedure
          begin
            Form26.Image1.Picture.Assign(Jpg);
            Form26.Show;
          end;
        );
      finally
        Jpg.Free;
      end;
    finally
      FS.Free;       
    end;
    //send feedback file received
    AContext.Connection.Socket.WriteLn('PICOK');
  end;
end;

或者这个:

type
  TMyNotify = class(TIdNotify)
  protected
    procedure DoNotify; override;
  public
    Jpg: TJpegImage;
    constructor Create;
    destructor Destroy; override;
  end;

constructor TMyNotify.Create(Stream: TStream);
begin
  inherited;
  Jpg := TJpegImage.Create;
  Jpg.LoadFromStream(Stream);
end;

destructor TMyNotify.Destroy;
begin
  Jpg.Free;
  inherited;
end;

procedure TMyNotify.DoNotify;
begin
  Form26.Image1.Picture.Assign(Jpg);
  Form26.Show;
end;

procedure TForm1.IdTCPServer1Execute(AContext: TIdContext);
var
  S, Filename: string;
  FS: TFileStream;
begin
  S := AContext.Connection.Socket.ReadLn;
  if S = 'PIC' then
  begin
    Filename := ExtractFilePath(Application.ExeName) + 'PIC\' + FormatDateTime('"PIC_"mm"-"dd"-"yyyy" "hh"_"nn"_"ss".jpg"', Now);
    FS := TFileStream.Create(Filename, fmCreate);
    try
      AContext.Connection.Socket.LargeStream := true;
      AContext.Connection.Socket.ReadStream(FS);
      FS.Position := 0;
      TMyNotify.Create(FS).Notify;
    finally
      FS.Free;       
    end;
    //send feedback file received
    AContext.Connection.Socket.WriteLn('PICOK');
  end;
end;