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...connect to an ftp server and download a file?
Autor: Thomas Stutz
[ Print tip ]  

Tip Rating (58):  
     


{
  The following function shows how to connect to a ftp server
  and download a file.
  It uses the functions from wininet.dll.

  You need a ProgressBar to show the progress and a Label to show progress informations.
}

uses
  
WinInet, ComCtrls;

function FtpDownloadFile(strHost, strUser, strPwd: string;
  Port: Integer; ftpDir, ftpFile, TargetFile: string; ProgressBar: TProgressBar): Boolean;

  function FmtFileSize(Size: Integer): string;
  begin
    if 
Size >= $F4240 then
      
Result := Format('%.2f', [Size / $F4240]) + ' Mb'
    else
    if 
Size < 1000 then
      
Result := IntToStr(Size) + ' bytes'
    else
      
Result := Format('%.2f', [Size / 1000]) + ' Kb';
  end;

const
  
READ_BUFFERSIZE = 4096;  // or 256, 512, ...
var
  
hNet, hFTP, hFile: HINTERNET;
  buffer: array[0..READ_BUFFERSIZE - 1] of Char;
  bufsize, dwBytesRead, fileSize: DWORD;
  sRec: TWin32FindData;
  strStatus: string;
  LocalFile: file;
  bSuccess: Boolean;
begin
  
Result := False;

  { Open an internet session }
  
hNet := InternetOpen('Program_Name', // Agent
                        
INTERNET_OPEN_TYPE_PRECONFIG, // AccessType
                        
nil,  // ProxyName
                        
nil// ProxyBypass
                        
0); // or INTERNET_FLAG_ASYNC / INTERNET_FLAG_OFFLINE

  {
    Agent contains the name of the application or
    entity calling the Internet functions
  }


  { See if connection handle is valid }
  
if hNet = nil then
  begin
    
ShowMessage('Unable to get access to WinInet.Dll');
    Exit;
  end;

  { Connect to the FTP Server }
  
hFTP := InternetConnect(hNet, // Handle from InternetOpen
                          
PChar(strHost), // FTP server
                          
port, // (INTERNET_DEFAULT_FTP_PORT),
                          
PChar(StrUser), // username
                          
PChar(strPwd),  // password
                          
INTERNET_SERVICE_FTP, // FTP, HTTP, or Gopher?
                          
0, // flag: 0 or INTERNET_FLAG_PASSIVE
                          
0);// User defined number for callback

  
if hFTP = nil then
  begin
    
InternetCloseHandle(hNet);
    ShowMessage(Format('Host "%s" is not available',[strHost]));
    Exit;
  end;

  { Change directory }
  
bSuccess := FtpSetCurrentDirectory(hFTP, PChar(ftpDir));

  if not bSuccess then
  begin
    
InternetCloseHandle(hFTP);
    InternetCloseHandle(hNet);
    ShowMessage(Format('Cannot set directory to %s.',[ftpDir]));
    Exit;
  end;

  { Read size of file }
  
if FtpFindFirstFile(hFTP, PChar(ftpFile), sRec, 0, 0) <> nil then
  begin
    
fileSize := sRec.nFileSizeLow;
    // fileLastWritetime := sRec.lastWriteTime
  
end else
  begin
    
InternetCloseHandle(hFTP);
    InternetCloseHandle(hNet);
    ShowMessage(Format('Cannot find file ',[ftpFile]));
    Exit;
  end;

  { Open the file }
  
hFile := FtpOpenFile(hFTP, // Handle to the ftp session
                       
PChar(ftpFile), // filename
                       
GENERIC_READ, // dwAccess
                       
FTP_TRANSFER_TYPE_BINARY, // dwFlags
                       
0); // This is the context used for callbacks.

  
if hFile = nil then
  begin
    
InternetCloseHandle(hFTP);
    InternetCloseHandle(hNet);
    Exit;
  end;

  { Create a new local file }
  
AssignFile(LocalFile, TargetFile);
  {$i-}
  
Rewrite(LocalFile, 1);
  {$i+}

  
if IOResult <> 0 then
  begin
    
InternetCloseHandle(hFile);
    InternetCloseHandle(hFTP);
    InternetCloseHandle(hNet);
    Exit;
  end;

  dwBytesRead := 0;
  bufsize := READ_BUFFERSIZE;

  while (bufsize > 0) do
  begin
    
Application.ProcessMessages;

    if not InternetReadFile(hFile,
                            @buffer, // address of a buffer that receives the data
                            
READ_BUFFERSIZE, // number of bytes to read from the file
                            
bufsize) then Break; // receives the actual number of bytes read

    
if (bufsize > 0) and (bufsize <= READ_BUFFERSIZE) then
      
BlockWrite(LocalFile, buffer, bufsize);
    dwBytesRead := dwBytesRead + bufsize;

    { Show Progress }
    
ProgressBar.Position := Round(dwBytesRead * 100 / fileSize);
    Form1.Label1.Caption := Format('%s of %s / %d %%',[FmtFileSize(dwBytesRead),FmtFileSize(fileSize) ,ProgressBar.Position]);
  end;

  CloseFile(LocalFile);

  InternetCloseHandle(hFile);
  InternetCloseHandle(hFTP);
  InternetCloseHandle(hNet);
  Result := True;
end;

 

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