Question

I’m trying to use Apache Commons Net for FTP file transfers.

Problem is files are intermittently arriving at the server corrupt. By ‘corrupt’ I mean that WinRAR tells me a ZIP file has an ‘Unexpected end of archive’. Sometimes the files are completely empty. I have noticed that this happens more for larger files (100kb+), however does happen for small files too (20kb).

I know for a fact that the source zip file being uploaded is valid, and is only 243kb.

I do not get any errors/exceptions from the code.

Here’s the code being executed:

int CON_TIMEOUT = (int) TimeUnit.SECONDS.toMillis(20); // fail if can't connect within 20 seconds
int LIVE_TIMEOUT = (int) TimeUnit.MINUTES.toMillis(5); // allow up to 5 minutes for data transfers

FTPClient client = new FTPClient();
client.setConnectTimeout(CON_TIMEOUT);
client.setDataTimeout(LIVE_TIMEOUT);
client.connect(host);
client.setSoTimeout(LIVE_TIMEOUT);
client.login(user, pass);
client.changeWorkingDirectory(dir);
log("client ready");

File file = new File(filePath);
String name = new Date().getTime() + "-" + file.getName();

InputStream fis = null;
try
{
    fis = new FileInputStream(file);
    if (!client.storeFile(name, fis))
        throw new RuntimeException("store failed");
    log("store " + name + " complete");
}
finally
{
    IOUtils.closeQuietly(fis);
    try
    {
        client.logout();
        log("logout");
    }
    catch (Throwable e)
    {
        log("logout failed", e);
    }
    try
    {
        client.disconnect();
        log("disconnect");
    }
    catch (Throwable e)
    {
        log("disconnect failed", e);
    }
}

and some logs:

2010-08-10 21:32:38 client ready
2010-08-10 21:32:49 store 1281439958234-file.zip complete
2010-08-10 21:32:49 logout
2010-08-10 21:32:49 disconnect
2010-08-10 21:32:50 client ready
2010-08-10 21:33:00 store 1281439970968-file.zip complete
2010-08-10 21:33:00 logout
2010-08-10 21:33:00 disconnect
2010-08-10 21:33:02 client ready
2010-08-10 21:33:11 store 1281439982234-file.zip complete
2010-08-10 21:33:11 logout
2010-08-10 21:33:11 disconnect
2010-08-10 21:33:15 client ready
2010-08-10 21:33:25 store 1281439995890-file.zip complete
2010-08-10 21:33:26 logout
2010-08-10 21:33:26 disconnect
2010-08-10 21:33:27 client ready
2010-08-10 21:33:36 store 1281440007531-file.zip complete
2010-08-10 21:33:36 logout
2010-08-10 21:33:36 disconnect
2010-08-10 21:33:37 client ready
2010-08-10 21:33:48 store 1281440017843-file.zip complete
2010-08-10 21:33:48 logout
2010-08-10 21:33:48 disconnect
2010-08-10 21:33:49 client ready
2010-08-10 21:33:59 store 1281440029781-file.zip complete
2010-08-10 21:33:59 logout
2010-08-10 21:33:59 disconnect
2010-08-10 21:34:00 client ready
2010-08-10 21:34:09 store 1281440040812-file.zip complete
2010-08-10 21:34:09 logout
2010-08-10 21:34:09 disconnect
2010-08-10 21:34:10 client ready
2010-08-10 21:34:23 store 1281440050859-file.zip complete
2010-08-10 21:34:24 logout
2010-08-10 21:34:24 disconnect
2010-08-10 21:34:25 client ready
2010-08-10 21:34:35 store 1281440065421-file.zip complete
2010-08-10 21:34:35 logout
2010-08-10 21:34:35 disconnect

Note that all of these were complete within 15 seconds, and all of the resulting files on the server are corrupt.

I have also tested without setting any timeouts and the problem still occurs.

Answer 1

Commons FTP defaults to Ascii file types. You want to set it to Binary when dealing with binary data like a ZIP file.

From http://commons.apache.org/net/api/org/apache/commons/net/ftp/FTPClient.html

The default settings for FTPClient are for it to use http://FTP.ASCII_FILE_TYPE , http://FTP.NON_PRINT_TEXT_FORMAT , http://FTP.STREAM_TRANSFER_MODE , and http://FTP.FILE_STRUCTURE . The only file types directly supported are http://FTP.ASCII_FILE_TYPE and http://FTP.BINARY_FILE_TYPE .

You want to do setFileType(FTP.BINARY_FILE_TYPE) before you send the file.