Apache Commons Net FTPClient and listFiles()

问题:

Can anyone explain me what's wrong with the following code? I tried different hosts, FTPClientConfigs, it's properly accessible via firefox/filezilla... The problem is I always get empty filelist without any exceptions (files.length == 0). I use commons-net-2.1.jar installed with Maven.

    FTPClientConfig config = new FTPClientConfig(FTPClientConfig.SYST_L8);

    FTPClient client = new FTPClient();
    client.configure(config);

    client.connect("c64.rulez.org");
    client.login("anonymous", "anonymous");
    client.enterRemotePassiveMode();

    FTPFile[] files = client.listFiles();
    Assert.assertTrue(files.length > 0);

回答1:

Found it!

The thing is you want to enter passive mode after you connect, but before you log in. Your code returns nothing for me, but this works for me:

import org.apache.commons.net.ftp.FTPClient;
import java.io.IOException;
import org.apache.commons.net.ftp.FTPFile;

public class BasicFTP {

    public static void main(String[] args) throws IOException {
        FTPClient client = new FTPClient();
        client.connect("c64.rulez.org");
        client.enterLocalPassiveMode();
        client.login("anonymous", "");
        FTPFile[] files = client.listFiles("/pub");
        for (FTPFile file : files) {
            System.out.println(file.getName());
        }
    }
}

Gives me this output:

c128
c64
c64.hu
incoming
plus4

回答2:

Only using enterLocalPassiveMode() did not work for me.

I used following code, which worked.

    ftpsClient.execPBSZ(0);
    ftpsClient.execPROT("P");
    ftpsClient.type(FTP.BINARY_FILE_TYPE);

Complete example is as below,

    FTPSClient ftpsClient = new FTPSClient();        

    ftpsClient.connect("Host", 21);

    ftpsClient.login("user", "pass");

    ftpsClient.enterLocalPassiveMode();

    ftpsClient.execPBSZ(0);
    ftpsClient.execPROT("P");
    ftpsClient.type(FTP.BINARY_FILE_TYPE);

    FTPFile[] files = ftpsClient.listFiles();

    for (FTPFile file : files) {
        System.out.println(file.getName());
    }

回答3:

usually the annonymous user doesn't need a password, try

client.login("anonymous", "");