This article presents a fully functional implementation of an FTP client.
FTP Wanderer is a multithreaded FTP client with the look and feel of Windows Explorer, and makes moving files between the Internet and your computer as simple as local file manipulation. This application uses WININET APIs to handle the FTP protocol, and while it’s not the most elegant way to connect to a FTP server, it does the job pretty well.
- All file transfer requests are handled in the background, so you don’t have to wait while files copy to continue browsing the current server. You can even connect to a different server while file transfers on another server are still in progress.
- The Transfer Manager shows all file transfers currently in progress plus the ones that are in the queue. You can configure how many transfers are processed simultaneously, so you don’t run out of resources.
- FTP Wanderer uses the Windows 9x/NT/XP style list boxes for displaying the contents of remote servers. It has all the familiar system icons and context menus.
- You can specify the number of times it should try to connect, and the time delay between connection attempts.
- Full Drag-and-Drop support. Simply drag one or more files or even complete folders onto FTP Wanderer’s file view area to transfer them to the location of the server that is currently connected.
- Easily configure FTP site settings such as username, password, port, initial remote folder, number of retries, and default download folder.
Here’s a brief description of some of the important classes of the application:
CMainFrame contains most of the code for managing the FTP connection. It takes care of connecting to the server, initiating up/downloads, and handling other FTP-related actions.
This is just a CListView-derived class that takes care of displaying the files and enabling you to sort them. When the application is busy downloading or sorting a directory listing, it can display an animation, just as Explorer does.
This class (= Site Manager) enables the user to manage FTP sites. You can add/change and delete sites and configure properties such as hostname, port, username, and password. The settings of each site are saved to disk using serializing.
CTransferManagerDlg (= Transfer Manager) takes care of queuing the file transfers. It shows all file transfers currently in progress plus the ones that are in the queue. You can configure how many transfers are processed simultaneously, so you don’t run out of resources. Each up/download is handled in a separate thread by initiating a CDownloadThread or CUploadThread thread.
Each download is handled in the background by using a separate thread. CDownloadThread creates a new connection with the FTP server and displays a progress dialog that tells you the status of the file transfer. When the download is completed (or aborted), it notifies the transfer manager so the UI can be updated.
Each upload is handled in the background, using a separate thread. CUploadThread creates a new connection with the FTP server and displays a progress dialog that tells you the status of the file transfer. When the upload is completed (or aborted), it notifies the transfer manager so the UI can be updated.
To Do List
Although this application has most of the features you might expect in a FTP client, there are a few things left to do:
- Drag-and-drop support out of the file view area to Explorer. I think this one is not that easy because this would probably “block” Explorer until the file transfer is completed. Any suggestions?
- Progress indication in the transfer manager. This is not really that hard to do, so it will probably be in the next release.
- Better asynchronous handling of getting a directory listing. The UI now does not respond when downloading a huge directory listing.
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