Delphi Indy TIdHttp 和 multipart/x-mixed-replace with Text 和 jpeg 图像

问题描述

我使用的是 Dahua Facial 终端，它有一个类似（CGI 风格）的 API 和一个 SDK。我问了一些关于 dll 转换的问题，但现在我也在尝试使用 de API。

监控 Facial 处理的事件的 API 是

http://192.168.1.201/cgi-bin/snapManager.cgi?action=attachFileProc&Flags[0]=Event&Events=[AccessControl]

是 multipart/x-mixed-replace 响应如何返回带有事件数据的文本/纯文本形式的第一个边界，以及带有事件快照的图像/jpeg 的边界。

使用有关 Indy 的在线信息和 Lebeau 发表的一些有用帖子，我使用 idHttp.IoHanlder.ReadLn(IndyTextEncoding_UTF8) 读取文本数据

我尝试使用 idHttp.IOHandler.ReadByte、ReadBytes、ReadStream 读取下一个边界（图像），但没有成功。

这是使用 idHttp.IoHandler.ReadLn 的响应

--myboundary
Content-Type: text/plain
Content-Length: 1035

Events[0].Alive=100
Events[0].CardName=Joao Test
Events[0].CardNo=0B8748EB
Events[0].CardType=0
Events[0].CreateTime=1616297700
Events[0].Door=0
Events[0].ErrorCode=0
Events[0].Method=15
Events[0].ReaderID=1
Events[0].Similarity=99
Events[0].SnapPath=/var/tmp/partsnap96.jpg
Events[0].Status=1
Events[0].Type=Entry
Events[0].UTC=1616297700
Events[0].UserID=1
Events[0].UserType=0

--myboundary
Content-Type: image/jpeg
Content-Length: 54235

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%&'()*456789:CDEFGHIJSTUVWXYZcdefghijstuvwxyz�������������������������������������������������������������������������

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我正在创建一个类来实现 API 和 SDK，在这种情况下 (API) 来管理事件我编写了一个线程类来使用事件 API 并在事件发生时同步数据，idHttp 归线程类和它在一个 Tdispositivo 类中，所以我为包含在主类中的每个 Tdispositivo 运行一个线程类。

这是来自线程的执行代码。 （忽略图像数据，因为我现在不知道如何正确获取它。

procedure TMonitor.Execute;
var
  Ret,URL,Chave,Valor : String;
  I,isInteger : Integer;
  Concluido : boolean;
  Tentativas: Integer;
begin
  Tentativas := 3;
  fAtivo := True;
  FContador := 0; //zerando contador
  //executa enquanto fAtivo for True e terminated for False
  while fAtivo and not self.Terminated do
    begin
      if fOwner.alive then
        begin
          //preparando URL
          With fOwner.Config do
            begin
              Url := 'http://'+ IP + ifthen(PortaWeb>=0,':'+PortaWeb.ToString,'')+'/cgi-bin/snapManager.cgi?action=attachFileProc&Flags[0]=Event&Events=[AccessControl]';
            end;
          //Incrementando contado
          Inc(fContador);
          //Efetuando o GET dentro de um try except para evitar interrupcao na thread
          Try
            ret := fHttp.Get(Url);
          except

          End;
          fOwner.doGet(fhttp.ResponseCode,fhttp.ResponseText);
          //tratando erros http
          if fHttp.ResponseCode <> 200 then
            begin
              case fHttp.ResponseCode of
                400: Erro(740,'Chamada ao terminal mal formada');
                401: Erro(741,'Chamada ao terminal não autorizada');
                403: Erro(743,'Recurso do servidor proibido');
                404: Erro(744,'Recurso do terminal não enconTrado');
                500: Erro(750,'Erro interno no processamento de chamadas do terminal');
                501: Erro(751,'Recurso do terminal não implementado');
              end;
              if (fContador >= Tentativas) then
                begin
                  Erro(700,'Falha ao conectar o dispositivo. Número de tentativas excedido');
                  fContador := 0;
                  //verificando se vai continuar tentando se reconectar
                  if fOwner.Config.Reconectar then
                    begin
                      Log('Aguardando para tentar reconectar o monitor ...');
                      Sleep(fOwner.Config.TempoEsperaReconectar);
                    end
                  else
                    begin
                      Log('Finalizando monitoramento por falha de comunicação');
                      Self.Stop;
                    end;
                end;
            end
          else
            begin
              //zerando contador após uma conexão bem sucedida;
              FContador := 0;
              //para evitar final do chunk ou close gracefully
              try
                if IsHeaderMediaType(fHttp.Response.ContentType,'multipart') then
                  begin
                    i := 0;
                    Concluido := False;
                    repeat
                      if (i >= 35) Or Concluido then
                        begin
                          //tirando snap antes de processar o evento para ver se diminui o delay
                          if FOwner.Config.SnapshotEvento then
                            fOwner.getSnapshot;
                          Synchronize(Evento);
                          Concluido := False;
                          i := 0;
                        end;
                      fLinha := fHttp.IOHandler.ReadLn(IndyTextEncoding_UTF8);
                      if Pos('Content-Length',fLinha) > 0 then
                        begin
                          i := 0;
                          Concluido := False;
                          fEvento.Limpar;
                        end
                      Else if Pos('Events[',fLinha) > 0 then
                        begin
                          if fOwner.Config.Depurar then
                            Log(fLinha);
                          Inc(I);
                          Chave := Trim(retPar(1,'=',retPar(2,'.',fLinha)));
                          Valor := Trim(retPar(2,fLinha));
                          if Valor = '' then
                            Valor := '0';
                          With fEvento do
                            begin
                              if Chave = 'Alive' then
                                Alive := ifthen(Valor = '',Valor.ToInteger)
                              else if Chave = 'CardName' then
                                CardName := ifthen(Trim(Valor) = '0','Não identificado',trim(Valor))
                              else if Chave = 'CardNo' then
                                begin
                                  if TryStrToInt(Valor,isInteger) then
                                    CardNo :=  ifthen(Valor = '','-1',Valor)
                                  else
                                    CardNo :=  WiegandHexToInt(Valor).ToString;
                                end
                              else if Chave = 'CardType' then
                                CardType := ifthen(Valor = '',-1,Valor.ToInteger)
                              else if Chave = 'CreateTime' then
                                CreateTime := UnixToDateTime(Valor.ToInt64,False)
                              else if Chave = 'Door' then
                                Door := ifThen(Valor = '',Valor.ToInteger)
                              else if Chave = 'ErrorCode' then
                                ErrorCode := ifThen(Valor = '',Valor.ToInteger)
                              else if Chave = 'EventBaseInfo.Action' then
                                EventBaseAction := Valor
                              else if Chave = 'EventBaseInfo.Code' then
                                EventBaseCode := Valor
                              else if Chave = 'EventBaseInfo.Index' then
                                EventBaseIndex := ifThen(Valor = '',Valor.ToInteger)
                              else if Chave = 'Method' then
                                Metodo := ifThen(Valor = '',Valor.ToInteger)
                              else if Chave = 'ReaderID' then
                                LeitorID := ifThen(Valor = '',Valor.ToInteger)
                              else if Chave = 'Similarity' then
                                Similaridade := ifthen(Valor = '',Valor.ToInteger)
                              else if Chave = 'SnapPath' then
                                snappath := Valor
                              else if Chave = 'Status' then
                                Status := ifthen(Valor = '',Valor.ToInteger)
                              else if Chave = '.Type' then
                                TipoAcesso := Valor
                              else if Chave = 'UTC' then
                                DataHora := UnixToDateTime(Valor.ToInt64,False)
                              else if Chave = 'UserID' then
                                UserID := ifthen(Valor = '',Valor.ToInteger)
                              else if Chave = 'UserType' then
                                begin
                                  i := 34;
                                  Concluido := True;
                                  UserType := ifthen(Valor = '',Valor.ToInteger);
                                end;
                            end;
                        end;
                    until fhttp.IOHandler.ClosedGracefully;
                  end;
              except

              end;
            end;
          inherited;
        end
      else
        begin
          //dispositivo não respondeu ao ping
          //verificando se vai continuar tentando se reconectar
          if fOwner.Config.Reconectar then
            begin
              Log('Aguardando para tentar reconectar o monitor ...');
              Sleep(fOwner.Config.TempoEsperaReconectar);
            end
          else
            begin
              Log('Finalizando monitoramento por falha de comunicação');
              Self.Stop;
            end;
          inherited;
        end;
    end;
  //rotina de finalização da thread
  if FHttp.Connected then
    begin
      try
        Fhttp.disconnect;
      except

      end;
    end;
end;

第一个问题，我可以吗？印地能做到吗？有什么建议吗？

第二个问题，我观察到在 GET 运行时检索数据的循环，当我在数据结束后尝试 readLn 时优雅地引发关闭。在 Firefox 中，GET 仍然在图像之后运行并且仍在工作，在我的情况下，GET 已完成并且 threand.execute 再次调用 GET。

是否可以保持 GET 运行以避免过早中断并在出现时处理新数据？

EDIT：当这部分代码运行时，行 NewDecoder := TIdMessageDecoderMIME(Decoder).ReadBody(BodyStream,MsgEnd); 优雅地结束，深入查看 Indy 代码我发现了 TIOHandler.ReadLn 如何执行 {{1 }} 当 CheckFordisconnect(True,True) 时，这会中断执行而不检索数据的最后一个字节。

考虑到这一点，我怀疑与 LTerm = -1 的关系始终为 Responde.KeepAlive，而 False 的内容始终为 Connection 这解释了为什么 Decoder.Readybody引发 close 并中断我的执行。

但是，如果我在例如上运行 api 调用。 Firefox，FF 获取图像后连接仍在运行，仅在超时时中断。

终端发送的标头上可能有什么东西吗？或者idHttp解析headers数据的方式？

Close gracefully

编辑：使用 New TIdHTTP hoNoReadMultipartMIME flag 示例，我编写了一个测试应用程序来尝试从边界获取图像

//part  of code after http.get

              mcptAttachment: begin
                BodyStream := TMemoryStream.Create;
                try
                  BodyStream.Position := 0;

                  NewDecoder := TIdMessageDecoderMIME(Decoder).ReadBody(BodyStream,MsgEnd); //<-- here comes a close gracefully               

                  jpg := TJPEGImage.Create;
                  try
                    BodyStream.Position := 0;
                    jpg.LoadFromStream(BodyStream);
                    jpg.SavetoFile('C:\Producao\API_SDK\Facial\teste.jpg');
                  finally
                    jpg.Free;
                    Decoder.Free;
                    Decoder := NewDecoder;
                  end;
                finally
                  BodyStream.Free;
                end;
              end;


//part of the code of tIOHandler.ReadLn

    // ReadFromSource blocks - do not call unless we need to
    else if LTermPos = -1 then begin
      // ReadLn needs to call this as data may exist in the buffer,but no EOL yet disconnected
      CheckFordisconnect(True,True); //The execution stops here whIoUt return the last bytes and premature finishing the code above with a close gracefully
      // Can only return -1 if timeout
      FReadLnTimedOut := ReadFromSource(True,ATimeout,False) = -1;
      if (not FReadLnTimedOut) and (ATimeout >= 0) then begin
        if GetElapsedTicks(LReadLnStartTime) >= UInt32(ATimeout) then begin
          FReadLnTimedOut := True;
        end;
      end;
      if FReadLnTimedOut then begin
        Result := '';
        Exit;
      end;

当调用 var Boundary,Line: string; Tcpstream: TIdTcpstream; NewDecoder,Decoder: TIdMessageDecoder; MsgEnd: Boolean; BodyStream: TStream; Jpg: TJpegImage; begin { The code below comes from Indy Project Blog by Remy Lebeau This connection requires Digest Auth,so i set BasicAuth to False,put the flag hoInProcessAuth And implement the OnAuthorization and OnSelectAuthorization,the select is needed to do something to the Authorization works,do not kNow why. } HTTP.HTTPOptions := [hoInProcessAuth,hoForceEncodeParams,honoreadMultipartMIME]; HTTP.Get('http://192.168.1.205/cgi-bin/snapManager.cgi?action=attachFileProc&Flags[0]=Event&Events=[AccessControl]'); //Here the response always return HTTP.Response.KeepAlive FALSE,so i exclude it from test if IsHeaderMediaType(HTTP.Response.ContentType,'multipart') then //and HTTP.Response.KeepAlive begin Boundary := ExtractHeaderSubItem(HTTP.Response.ContentType,'boundary',QuoteHTTP); repeat Line := HTTP.IOHandler.ReadLn; until (Line = ('--' + Boundary)) or (Line = ('--' + Boundary + '--')); Tcpstream := TIdTcpstream.Create(HTTP); try Decoder := TIdMessageDecoderMIME.Create(nil); try TIdMessageDecoderMIME(Decoder).MIMEBoundary := Boundary; MsgEnd := False; repeat TIdMessageDecoderMIME(Decoder).sourceStream := Tcpstream; TIdMessageDecoderMIME(Decoder).FreeSourceStream := False; Decoder.ReadHeader; case Decoder.PartType of mcptText: begin BodyStream := TMemoryStream.Create; try NewDecoder := TIdMessageDecoderMIME(Decoder).ReadBody(BodyStream,MsgEnd); try BodyStream.Position := 0; mLog.Lines.LoadFromStream(BodyStream); //<-- OK i got the text data from body and showing in a memo finally Decoder.Free; Decoder := NewDecoder; end; finally BodyStream.Free; end; end; mcptAttachment: begin BodyStream := TMemoryStream.Create; try BodyStream.Position := 0; NewDecoder := TIdMessageDecoderMIME(Decoder).ReadBody(BodyStream,MsgEnd); //<-- here comes a close gracefully,//so i debug the ReadBody and found a exception on line 438 of idMessadeCoderMime // LLine := ReadLnRFC(VMsgEnd,LF,LEncoding{$IFDEF STRING_IS_ANSI},LEncoding{$ENDIF}); {do not localize} //When it try to read a exception occurs and the connection closes gracefully //but it read a lot of data befora except,so i thinking is something about a end of msg missing or misformed jpg := TJPEGImage.Create; try BodyStream.Position := 0; jpg.LoadFromStream(BodyStream); jpg.SavetoFile('C:\Producao\API_SDK\Facial\teste.jpg'); finally jpg.Free; Decoder.Free; Decoder := NewDecoder; end; finally BodyStream.Free; end; end; mcptIgnore: begin FreeAndNil(Decoder); Decoder := TIdMessageDecoderMIME.Create(nil); TIdMessageDecoderMIME(Decoder).MIMEBoundary := Boundary; end; mcptEOF: begin FreeAndNil(Decoder); MsgEnd := True; end; end; until (Decoder = nil) or MsgEnd; finally Decoder.Free; end; finally Tcpstream.Free; end; end; end; 时，部分代码 mcptAttachment 会运行 readbody 函数，读取字节直到它在达到 'Content-Length' 大小之前崩溃。 我试图在它崩溃时进行隔离，但是可以肯定的是，当它尝试读取下一个数据时会发生错误。但我还没有在 indy 源上找到异常的触发器

编辑：得到一个图像，但无法继续阅读，直到服务器关闭连接导致响应已经关闭。

工作代码

NewDecoder := Decoder.ReadBody(BodyStream,MsgEnd);

解决方法

您可以使用 TIdHTTP 完成您的要求，但这需要一些额外的工作。 Indy 网站上的以下博客文章提供了详细信息：

https://www.indyproject.org/2014/03/05/new-tidhttp-honoreadmultipartmime-flag/

简而言之，您需要在 hoNoReadMultipartMIME 属性中启用 TIdHTTP.HTTPOptions 标志，以便 TIdHTTP.Get() 不会尝试从 TIdHTTP.IOHandler收到 HTTP 标头后。这将允许您自己读取 MIME 数据。您可以使用 Indy 的 TIdMessageDecoderMIME 类来帮助阅读。博客文章中提供了一个代码示例。