有关TServerSocket和TClientSocket的问题

Question

在TServerSokcet中调用SendBuf发送4000的数据包,在TClientSocket的ClientSocketRead事件中用Socket.ReceiveBuf接收数据包,然后用日志记录,在日志中看到发送的记录与接收的记录不一致,会有几个数据包接收不到,我用的是TCP方式,不应该会经常丢失（功能 :从一台电脑读文件到别一台电脑),请高手指教....

Answer 1

我也遇到同样的问题,不知道是怎么回事,感觉TClientSocket的ClientSocketRead不怎么可靠

Answer 2

bds已经没有这控件了，可能是它自己也觉得不可靠吧

Answer 3

ReceiveBuf并不一定能一次性接收完整的数据。
在调用该函数前，先通过Socket.ReceiveLength获取数据长度，然后检查ReceiveBuf函数的返回值，这个返回值表示该函数实际接收了的数据。如果返回值小于Socket.ReceiveLength获取的数据长度，则需要再次调用ReceiveBuf函数，直至所有数据全部获取。例如:
procedure TForm1.SocketRead(Sender: TObject; Socket: TCustomWinSocket);
var
  iLength   : Integer;
  iReceived : Integer;
  bBuffer   : array of Byte;
begin
  iLength := Socket.ReceiveLength;
  while iLength > 0 do
  begin
    SetLength (bBuffer, iLength);
    iReceived := Socket.ReceiveBuf(bBuffer[0], iLength);
    //处理数据
    ......
    iLength := iLength - iReceived;
  end;
  bBuffer := nil;
end;

Answer 4

接收到的数据保存在缓冲区里，ReceiveLength就是缓冲区里接收到的数据的长度

Answer 5

jadeluo(秀峰)的解答很详细，同意

Answer 6

你要确认你使用的是blocking方式还是其他。
一般服务器为threadblocking,客户端为blocking。

Answer 7

提点不同意见
jadeluo(秀峰)的回答我感觉不是最佳的，因为ReceiveLength有时候并不准确，建议你最好先把文件的大小传过来，或者把每次发送的数据包大小先传过来。这样才能保证完整的收到发送的数据。

Answer 8

我的代码并不是用来解决“如何接收一个完整的应用层通讯协议包“的。
这段代码解决的问题是“ReceiveBuf并不一定能一次性接收完整的数据”，代码所给出的方法能够正确、完整地接收并处理已经到达的数据(不是通讯协议包)。
再把代码补充得更详细些：
procedure TForm1.SocketRead(Sender: TObject; Socket: TCustomWinSocket);
var
  iLength   : Integer;
  iReceived : Integer;
  bBuffer   : array of Byte;
  iLoop     : Integer;
begin
  iLength := Socket.ReceiveLength;
  while iLength > 0 do
  begin
    SetLength (bBuffer, iLength);
    iReceived := Socket.ReceiveBuf(bBuffer[0], iLength);
    //处理数据(下面的代码需要按照通讯协议来对已经接收的数据进行处理)
    for iLoop := 0 to iReceived - 1 do
    begin
      ......
    end;
    ......
    iLength := iLength - iReceived;
  end;
  bBuffer := nil;
end;

Answer 9

到达的数据并不一定就是完整的发送的数据。
我无意与你争论，只是想说明这个问题。如果想完整的接收到另一端发送的数据，用ReceiveLength是不可靠的

Answer 10

我也遇到ServerSocket, ClientSocket快速发送丢包的情况。

Answer 11

用阻塞模式传送，局域网速度达到10M左右发送端：
unit UniClient;interfaceuses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, ScktComp, StdCtrls, shlobj, ActiveX;type
  TForm1 = class(TForm)
    Button1: TButton;
    ClientSocket1: TClientSocket;
    OpenDialog1: TOpenDialog;
    Edit1: TEdit;
    CSocket_Cmd: TClientSocket;
    Memo1: TMemo;
    Button2: TButton;
    Memo2: TMemo;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure FormClose(Sender: TObject; var Action: TCloseAction);
  private
    { Private declarations }
  public
    { Public declarations }
  end;var
  Form1: TForm1;
  Path: string; //起始路径
  IsClose: Boolean;
implementation{$R *.dfm}function BrowseCallbackProc(hwnd: HWND; uMsg: UINT; lParam: Cardinal; lpData: Cardinal): integer; stdcall;
begin
  if uMsg = BFFM_INITIALIZED then
    result := SendMessage(Hwnd, BFFM_SETSELECTION, Ord(TRUE), Longint(PChar(Path)))
  else
    result := 1
end;function SelDir(const Caption: string; const Root: WideString; out Directory: string): Boolean;
var
  WindowList: Pointer;
  BrowseInfo: TBrowseInfo;
  Buffer: PChar;
  RootItemIDList, ItemIDList: PItemIDList;
  ShellMalloc: IMalloc;
  IDesktopFolder: IShellFolder;
  Eaten, Flags: LongWord;
begin
  Result := False;
  Directory := '';
  FillChar(BrowseInfo, SizeOf(BrowseInfo), 0);
  if (ShGetMalloc(ShellMalloc) = S_OK) and (ShellMalloc <> nil) then
  begin
    Buffer := ShellMalloc.Alloc(MAX_PATH);
    try
      RootItemIDList := nil;
      if Root <> '' then begin
        SHGetDesktopFolder(IDesktopFolder);
        IDesktopFolder.ParseDisplayName(Application.Handle, nil, POleStr(Root), Eaten, RootItemIDList, Flags);
      end;
      with BrowseInfo do begin
        hwndOwner := Application.Handle;
        pidlRoot := RootItemIDList;
        pszDisplayName := Buffer;
        lpszTitle := PChar(Caption);
        ulFlags := BIF_RETURNONLYFSDIRS;
        lpfn := @BrowseCallbackProc;
        lParam := BFFM_INITIALIZED;
      end;
      WindowList := DisableTaskWindows(0);
      try
        ItemIDList := ShBrowseForFolder(BrowseInfo);
      finally
        EnableTaskWindows(WindowList);
      end;
      Result := ItemIDList <> nil;
      if Result then begin
        ShGetPathFromIDList(ItemIDList, Buffer);
        ShellMalloc.Free(ItemIDList);
        Directory := Buffer;
      end;
    finally
      ShellMalloc.Free(Buffer);
    end;
  end;
end;procedure Delay(dwMilliseconds: Longint);
var
  iStart, iStop: DWORD;
begin
  iStart := GetTickCount;
  repeat
    iStop := GetTickCount;
    Application.ProcessMessages;
  until (iStop - iStart) >= dwMilliseconds;
end;function SubStr(Str: string; FindStr: string; Index: Integer): string;
var
  i, x: Integer;
begin
  Result := '';
  i := Pos(FindStr, Str);
  x := 0;
  while i > 0 do
  begin
    Inc(x);
    if x = Index then
    begin
      Result := Trim(Copy(Str, 1, i - 1));
      Exit;
    end;
    Delete(str, 1, i + length(FindStr) - 1);
    i := Pos(FindStr, Str);
  end;
  if (x + 1 = Index) and (str <> '') then
    Result := Trim(Str);end;function GetFileSize(const FileName: string): LongInt;
var
  SearchRec: TSearchRec;
begin
  try
    if FindFirst(ExpandFileName(FileName), faAnyFile, SearchRec) = 0 then
      Result := SearchRec.Size
    else Result := -1;
  finally
    SysUtils.FindClose(SearchRec);
  end;
end;procedure GetAllFile(FileList: TStrings; const Path: string; FileEx: string = '*.*');
var
  f: TSearchRec;
  Ret: Integer;
  p: string;
begin
  FileEx := UpperCase(FileEx);
  Ret := FindFirst(Path + '\*.*', faAnyFile, f);
  while Ret = 0 do
  begin
    if f.Attr = faDirectory then
    begin
      if (f.Name <> '.') and (f.Name <> '..') then
        GetAllFile(FileList, Path + '\' + f.Name)
    end
    else
      if (FileEx = '*.*') or (UpperCase(ExtractFileExt(f.Name)) = FileEx) then
      begin
        p := Path + '\' + f.Name;
        FileList.Append(IntToStr(GetFileSize(p)) + '|' + p);
      end;
    Ret := FindNext(f)
  end;
  FindClose(f)
end;function ReadReceiveText(Socket: TCustomWinSocket; TimeOut: Longint = 60000): string;
var
  StartTick, CurrentTick: Integer;
begin
  StartTick := GetTickCount;
  CurrentTick := GetTickCount;
  while (CurrentTick - StartTick < TimeOut) and
    (not IsClose) do
  begin
    Result := Socket.ReceiveText;
    if Result <> '' then
      break
    else
    begin
      Delay(100);
      CurrentTick := GetTickCount;
    end;
  end;end;procedure TForm1.Button1Click(Sender: TObject);
var
  s: TWinSocketStream;
  f: TFileStream;
  i, x: integer;
  m: TMemoryStream;
  fileName, ReceiveText, str, str2: string;
  FileList: TStringList;
begin
//  if not OpenDialog1.Execute then Exit;
//去掉无用的路径，用于传送到接收端
  FileList := TStringList.Create;
  FileList.Assign(Memo1.Lines);
  x := Length(IncludeTrailingBackslash(Path));
  for i := 0 to FileList.Count - 1 do
  begin
    str := SubStr(FileList[i], '|', 1);
    str2 := SubStr(FileList[i], '|', 2);
    Delete(str2, 1, x);
    FileList[i] := str + '|' + str2;
  end;
  ClientSocket1.Address := Edit1.Text;
  ClientSocket1.Port := 1234;
  ClientSocket1.Open;
  s := TWinSocketStream.Create(ClientSocket1.Socket, 60000);
  try
    m := TMemoryStream.Create;
    FileList.SaveToStream(m);
    s.CopyFrom(m, 0);
    str := #123#124'filelist_send_over'#123#124;
    s.WriteBuffer(str[1], Length(str));
//    sleep(2000);
    ReceiveText := ReadReceiveText(ClientSocket1.Socket);
//    showmessage(ReceiveText);//开始发送文件
    FileList.Assign(Memo1.Lines);
    i := 0;
    while True do
//    for i := 0 to Memo1.Lines.Count - 1 do
    begin      fileName := SubStr(FileList[i], '|', 2);
      f := TFileStream.Create(FileName, fmShareDenyWrite);
      s.CopyFrom(f, 0);
      f.Free;
      Memo2.Lines.Add(FileList[i]);
      ReceiveText := ReadReceiveText(ClientSocket1.Socket);
      inc(i);
      if i >= FileList.Count then
        Break;
    end;  finally
    s.Free;
//    f.Free;
    ClientSocket1.Close;
  end;
end;procedure TForm1.Button2Click(Sender: TObject);
var
  Path1: string;
begin
  Path := Edit1.Text;
  if SelDir('SelectDirectory Sample', '', Path) then
  begin
    GetAllFile(Memo1.Lines, Path);
  end;
end;procedure TForm1.FormCreate(Sender: TObject);
begin
  IsClose := False;
end;procedure TForm1.FormClose(Sender: TObject; var Action: TCloseAction);
begin
  IsClose := True;
end;end.

Answer 12

接收端：
unit Uniserver;interfaceuses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, ScktComp;type
  TClientThread = class(TServerClientThread)
  private
  public
    procedure ClientExecute; override;
  end;
type
  TForm1 = class(TForm)
    ServerSocket1: TServerSocket;
    procedure ServerSocket1GetThread(Sender: TObject;
      ClientSocket: TServerClientWinSocket;
      var SocketThread: TServerClientThread);
    procedure FormCreate(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;var
  Form1: TForm1;implementation{$R *.dfm}{ TClientThread }function SubStr(Str: string; FindStr: string; Index: Integer): string;
var
  i, x: Integer;
begin
  Result := '';
  i := Pos(FindStr, Str);
  x := 0;
  while i > 0 do
  begin
    Inc(x);
    if x = Index then
    begin
      Result := Trim(Copy(Str, 1, i - 1));
      Exit;
    end;
    Delete(str, 1, i + length(FindStr) - 1);
    i := Pos(FindStr, Str);
  end;
  if (x + 1 = Index) and (str <> '') then
    Result := Trim(Str);end;procedure TClientThread.ClientExecute;
type
  TFileInf = record
    Name: string;
    Size: Longint;
  end;
const
  filelist_send_over = #123#124'filelist_send_over'#123#124;var
  ReceiveBuffer: array[0..4095] of Char;
  SocketStream: TWinSocketStream;
  BytesRead: Integer;
  F: TFileStream;
  FileList: TStringList;
  i: integer;
  CurrentFile: TFileInf;
  Path, CurrentPath, Str: string;
begin
  while not Terminated and ClientSocket.Connected do
  begin
    try
      SocketStream := TWinSocketStream.Create(ClientSocket, 60000);
      FileList := TStringList.Create;//      F := TFileStream.Create('c:\afile.exe', fmCreate);
      try
        FillChar(ReceiveBuffer, 10, 0);
        if SocketStream.WaitForData(5000) then
          repeat
            BytesRead := SocketStream.Read(ReceiveBuffer, SizeOf(ReceiveBuffer));
            if BytesRead = 0 then
            begin
//              ClientSocket.Close
              break;
            end
            else
            begin
              FileList.Text := FileList.Text + ReceiveBuffer;
            end;
          until not SocketStream.WaitForData(2000);        i := Pos(filelist_send_over, FileList.Text);
        if i > 0 then
        begin
          ClientSocket.SendText('ok');
          Str := FileList.Text;
          Delete(Str, i, MaxInt);
          FileList.Text := Str;
//          break;
        end;        Path := 'c:\test\';
        i := 0;        while true do
        begin
        //当前文件的信息
          CurrentFile.Name := Path + SubStr(FileList[i], '|', 2);
          CurrentFile.Size := StrToInt64(SubStr(FileList[i], '|', 1));
        //检查文件路径
          CurrentPath := ExtractFilePath(CurrentFile.Name);
          if not DirectoryExists(CurrentPath) then
            ForceDirectories(CurrentPath);          F := TFileStream.Create(CurrentFile.Name, fmCreate);
          if SocketStream.WaitForData(5000) then
            repeat
              BytesRead := SocketStream.Read(ReceiveBuffer, SizeOf(ReceiveBuffer));
              if BytesRead = 0 then
              begin
                ClientSocket.Close;
//                  break;
              end
              else
              begin
                F.WriteBuffer(ReceiveBuffer, BytesRead);
                if f.Size = CurrentFile.Size then
                begin
                  ClientSocket.SendText('ok');
                  f.Free;
                  break;
                end;
              end;
            until not SocketStream.WaitForData(2000);
          inc(i);
          if i >= FileList.Count then
            Break;
        end;      finally
        SocketStream.Free;
        ClientSocket.Close;
//        f.Free;
      end;
    except
    end;
  end;
end;
procedure TForm1.ServerSocket1GetThread(Sender: TObject;
  ClientSocket: TServerClientWinSocket;
  var SocketThread: TServerClientThread);
begin
  SocketThread := TClientThread.Create(False, ClientSocket);end;procedure TForm1.FormCreate(Sender: TObject);
begin
  ServerSocket1.Port := 1234;
  ServerSocket1.Open;
end;end.支持多文件同线程传送！！

Answer 13

jadeluo(秀峰)的解答很详细，同意   另外,发送的数据报越大.丢失的情况越严重.
   最好一次性发送较小的数据量,2000以下最好

Answer 14

在DELPHI帮助里面,也着重说了不宜取ReceiveLength后根据长度再RECV读出数据.
不过象秀峰那样,把这个数值作为参考来分配空间读数据也行,
关键只在判断ReceiveBuf的返回值把握住...楼主丢数据失误关键就是这儿处理得不妥吧.