使用 apache commons-net FTPClient 传输原始二进制文件

问题描述

更新:已解决

我在调用 FTPClient.setFileType() 之前我登录，导致 FTP 服务器使用默认模式 (ASCII) 否重要 what 我将它设置为.另一方面，客户端表现得好像文件类型已正确设置.BINARY 模式现在完全按照需要工作，在所有情况下都可以逐字节传输文件.我所要做的就是在wireshark 中嗅探一下流量，然后使用netcat 模拟FTP 命令以查看发生了什么.为什么我前两天没有想到！?谢谢大家的帮助！

I was calling FTPClient.setFileType() before I logged in, causing the FTP server to use the default mode (ASCII) no matter what I set it to. The client, on the other hand, was behaving as though the file type had been properly set. BINARY mode is now working exactly as desired, transporting the file byte-for-byte in all cases. All I had to do was a little traffic sniffing in wireshark and then mimicing the FTP commands using netcat to see what was going on. Why didn't I think of that two days ago!? Thanks, everyone for your help!

我有一个 utf-16 编码的 xml 文件，我使用 apache 的 commons-net-2.0 java 库的 FTPClient 从 FTP 站点下载该文件.它支持两种传输模式:ASCII_FILE_TYPE 和 BINARY_FILE_TYPE，区别在于 ASCII 将用适当的本地行分隔符(' ' 或只是 ' ' - 十六进制，0x0d0a 或只是 0x0a).我的问题是:我有一个 utf-16 编码的测试文件，其中包含以下内容:

I have an xml file, utf-16 encoded, which I am downloading from an FTP site using apache's commons-net-2.0 java library's FTPClient. It offers support for two transfer modes: ASCII_FILE_TYPE and BINARY_FILE_TYPE, the difference being that ASCII will replace line separators with the appropriate local line separator (' ' or just ' ' -- in hex, 0x0d0a or just 0x0a). My problem is this: I have a test file, utf-16 encoded, that contains the following:

<?xml version='1.0' encoding='utf-16'?>
<数据>
    <blah>blah</blah>
</data>

这是十六进制:
<代码>0000000: 003c 003f 0078 006d 006c 0020 0076 0065 .<.?.x.m.l..v.e
0000010: 0072 0073 0069 006f 006e 003d 0027 0031 .r.s.i.o.n.=.'.1
<代码>0000020: 002e 0030 0027 0020 0065 006e 0063 006f ...0.'..e.n.c.o
0000030: 0064 0069 006e 0067 003d 0027 0075 0074 .d.i.n.g.=.'.u.t
0000040: 0066 002d 0031 0036 0027 003f 003e 000a .f.-.1.6.'.?.>..
0000050: 003c 0064 0061 0074 0061 003e 000a 0009 .<.d.a.t.a.>....
0000060: 003c 0062 006c 0061 0068 003e 0062 006c .<.b.l.a.h.>.b.l
0000070: 0061 0068 003c 002f 0062 006c 0061 0068 .a.h.<./.b.l.a.h
0000080: 003e 000a 003c 002f 0064 0061 0074 0061 .>...<./.d.a.t.a
0000090: 003e 000a                                              ;              .>..

Here's the hex:
0000000: 003c 003f 0078 006d 006c 0020 0076 0065 .<.?.x.m.l. .v.e
0000010: 0072 0073 0069 006f 006e 003d 0027 0031 .r.s.i.o.n.=.'.1
0000020: 002e 0030 0027 0020 0065 006e 0063 006f ...0.'. .e.n.c.o
0000030: 0064 0069 006e 0067 003d 0027 0075 0074 .d.i.n.g.=.'.u.t
0000040: 0066 002d 0031 0036 0027 003f 003e 000a .f.-.1.6.'.?.>..
0000050: 003c 0064 0061 0074 0061 003e 000a 0009 .<.d.a.t.a.>....
0000060: 003c 0062 006c 0061 0068 003e 0062 006c .<.b.l.a.h.>.b.l
0000070: 0061 0068 003c 002f 0062 006c 0061 0068 .a.h.<./.b.l.a.h
0000080: 003e 000a 003c 002f 0064 0061 0074 0061 .>...<./.d.a.t.a
0000090: 003e 000a                                                            .>..

当我对这个文件使用 ASCII 模式时，它会正确地逐字节传输；结果具有相同的 md5sum.伟大的.当我使用 BINARY 传输模式时，除了将 InputStream 中的字节洗牌到 OutputStream 之外，它不应该做任何事情，结果是换行符 (0x0a) 被转换为回车 + 换行符对 (0x0d0a).这是二进制传输后的十六进制:

When I use ASCII mode for this file it transfers correctly, byte-for-byte; the result has the same md5sum. Great. When I use BINARY transfer mode, which is not supposed to do anything but shuffle bytes from an InputStream into an OutputStream, the result is that the newlines (0x0a) are converted to carriage return + newline pairs (0x0d0a). Here's the hex after binary transfer:

0000000: 003c 003f 0078 006d 006c 0020 0076 0065 .<.?.x.m.l..v.e
0000010: 0072 0073 0069 006f 006e 003d 0027 0031 .r.s.i.o.n.=.'.1
<代码>0000020: 002e 0030 0027 0020 0065 006e 0063 006f ...0.'..e.n.c.o
0000030: 0064 0069 006e 0067 003d 0027 0075 0074 .d.i.n.g.=.'.u.t
0000040: 0066 002d 0031 0036 0027 003f 003e 000d .f.-.1.6.'.?.>..
0000050: 0a00 3c00 6400 6100 7400 6100 3e00 0d0a ..<.d.a.t.a.>...
0000060: 0009 003c 0062 006c 0061 0068 003e 0062 ...<.b.l.a.h.>.b
0000070: 006c 0061 0068 003c 002f 0062 006c 0061 .l.a.h.<./.b.l.a
0000080: 0068 003e 000d 0a00 3c00 2f00 6400 6100 .h.>....<./.d.a.
0000090: 7400 6100 3e00 0d0a                  &n;                     ta>..

0000000: 003c 003f 0078 006d 006c 0020 0076 0065 .<.?.x.m.l. .v.e
0000010: 0072 0073 0069 006f 006e 003d 0027 0031 .r.s.i.o.n.=.'.1
0000020: 002e 0030 0027 0020 0065 006e 0063 006f ...0.'. .e.n.c.o
0000030: 0064 0069 006e 0067 003d 0027 0075 0074 .d.i.n.g.=.'.u.t
0000040: 0066 002d 0031 0036 0027 003f 003e 000d .f.-.1.6.'.?.>..
0000050: 0a00 3c00 6400 6100 7400 6100 3e00 0d0a ..<.d.a.t.a.>...
0000060: 0009 003c 0062 006c 0061 0068 003e 0062 ...<.b.l.a.h.>.b
0000070: 006c 0061 0068 003c 002f 0062 006c 0061 .l.a.h.<./.b.l.a
0000080: 0068 003e 000d 0a00 3c00 2f00 6400 6100 .h.>....<./.d.a.
0000090: 7400 6100 3e00 0d0a                                        t.a.>...

它不仅转换换行符(它不应该)，而且它不尊重 utf-16 编码(不是我希望它知道它应该知道，它只是一个愚蠢的 FTP 管道).如果不进行进一步处理以重新对齐字节，则结果是不可读的.我只会使用 ASCII 模式，但我的应用程序也会在同一管道中移动 real 二进制数据(mp3 文件和 jpeg 图像).在这些二进制文件上使用 BINARY 传输模式还会导致它们在其内容中注入随机 0x0d，由于二进制数据通常包含合法的0x0d0a 序列.如果我在这些文件上使用 ASCII 模式，那么聪明"的 FTPClient 会将这些 0x0d0as 转换为 0x0a 无论如何我都会使文件不一致做.

Not only does it convert the newline characters (which it shouldn't), but it doesn't respect the utf-16 encoding (not that I would expect it to know that it should, it's just a dumb FTP pipe). The result is unreadable without further processing to realign the bytes. I would just use ASCII mode, but my application will also be moving real binary data (mp3 files and jpeg images) across the same pipe. Using the BINARY transfer mode on these binary files also causes them to have random 0x0ds injected into their contents, which can't safely be removed since the binary data often contains legitimate 0x0d0a sequences. If I use ASCII mode on these files, then the "clever" FTPClient converts these 0x0d0as into 0x0a leaving the file inconsistent no matter what I do.

我想我的问题是:有没有人知道任何用于 java 的好的 FTP 库只是将该死的字节从那里移动到这里，或者我将不得不破解 apache commons-net-2.0 并为这个简单的应用程序维护我自己的 FTP 客户端代码?有没有其他人处理过这种奇怪的行为?任何建议将不胜感激.

I guess my question(s) is(are): does anyone know of any good FTP libraries for java that just move the damned bytes from there to here, or am I going to have to hack up apache commons-net-2.0 and maintain my own FTP client code just for this simple application? Has anyone else dealt with this bizarre behavior? Any suggestions would be appreciated.

我查看了 commons-net 源代码，它看起来不像是使用 BINARY 模式时出现的奇怪行为.但是它在 BINARY 模式下读取的 InputStream 只是一个包裹在套接字 InputStream 周围的 java.io.BufferedInptuStream.这些较低级别的 java 流是否做过任何奇怪的字节操作?如果他们这样做了，我会感到震惊，但我看不出这里还会发生什么.

I checked out the commons-net source code and it doesn't look like it's responsible for the weird behavior when BINARY mode is used. But the InputStream it's reading from in BINARY mode is just a java.io.BufferedInptuStream wrapped around a socket InputStream. Do these lower level java streams ever do any weird byte-manipulation? I would be shocked if they did, but I don't see what else could be going on here.

编辑 1:

这是一段模仿我下载文件的最小代码.要编译，只需执行

Here's a minimal piece of code that mimics what I'm doing to download the file. To compile, just do

javac -classpath /path/to/commons-net-2.0.jar Main.java

要运行，您需要目录/tmp/ascii 和/tmp/binary 以将文件下载到，以及设置有文件的 ftp 站点.代码还需要配置适当的 ftp 主机、用户名和密码.我将文件放在我的测试 ftp 站点上的 test/文件夹下，并调用文件 test.xml.测试文件至少应该多于一行，并且是 utf-16 编码的(这可能不是必需的，但有助于重现我的确切情况).在打开一个新文件并输入上面引用的 xml 文本后，我使用了 vim 的 :set fileencoding=utf-16 命令.最后，要运行，只需执行

To run, you'll need directories /tmp/ascii and /tmp/binary for the file to download to, as well as an ftp site set up with the file sitting in it. The code will also need to be configured with the appropriate ftp host, username and password. I put the file on my testing ftp site under the test/ folder and called the file test.xml. The test file should at least have more than one line, and be utf-16 encoded (this may not be necessary, but will help to recreate my exact situation). I used vim's :set fileencoding=utf-16 command after opening a new file and entered the xml text referenced above. Finally, to run, just do

java -cp .:/path/to/commons-net-2.0.jar Main

代码:

(注意:此代码已修改为使用自定义 FTPClient 对象，链接在下面的EDIT 2"下)

(NOTE: this code modified to use custom FTPClient object, linked below under "EDIT 2")

import java.io.*;
import java.util.zip.CheckedInputStream;
import java.util.zip.CheckedOutputStream;
import java.util.zip.CRC32;
import org.apache.commons.net.ftp.*;

public class Main implements java.io.Serializable
{
    public static void main(String[] args) throws Exception
    {
        Main main = new Main();
        main.doTest();
    }

    private void doTest() throws Exception
    {
        String host = "ftp.host.com";
        String user = "user";
        String pass = "pass";

        String asciiDest = "/tmp/ascii";
        String binaryDest = "/tmp/binary";

        String remotePath = "test/";
        String remoteFilename = "test.xml";

        System.out.println("TEST.XML ASCII");
        MyFTPClient client = createFTPClient(host, user, pass, org.apache.commons.net.ftp.FTP.ASCII_FILE_TYPE);
        File path = new File("/tmp/ascii");
        downloadFTPFileToPath(client, "test/", "test.xml", path);
        System.out.println("");

        System.out.println("TEST.XML BINARY");
        client = createFTPClient(host, user, pass, org.apache.commons.net.ftp.FTP.BINARY_FILE_TYPE);
        path = new File("/tmp/binary");
        downloadFTPFileToPath(client, "test/", "test.xml", path);
        System.out.println("");

        System.out.println("TEST.MP3 ASCII");
        client = createFTPClient(host, user, pass, org.apache.commons.net.ftp.FTP.ASCII_FILE_TYPE);
        path = new File("/tmp/ascii");
        downloadFTPFileToPath(client, "test/", "test.mp3", path);
        System.out.println("");

        System.out.println("TEST.MP3 BINARY");
        client = createFTPClient(host, user, pass, org.apache.commons.net.ftp.FTP.BINARY_FILE_TYPE);
        path = new File("/tmp/binary");
        downloadFTPFileToPath(client, "test/", "test.mp3", path);
    }

    public static File downloadFTPFileToPath(MyFTPClient ftp, String remoteFileLocation, String remoteFileName, File path)
        throws Exception
    {
        // path to remote resource
        String remoteFilePath = remoteFileLocation + "/" + remoteFileName;

        // create local result file object
        File resultFile = new File(path, remoteFileName);

        // local file output stream
        CheckedOutputStream fout = new CheckedOutputStream(new FileOutputStream(resultFile), new CRC32());

        // try to read data from remote server
        if (ftp.retrieveFile(remoteFilePath, fout)) {
            System.out.println("FileOut: " + fout.getChecksum().getValue());
            return resultFile;
        } else {
            throw new Exception("Failed to download file completely: " + remoteFilePath);
        }
    }

    public static MyFTPClient createFTPClient(String url, String user, String pass, int type)
        throws Exception
    {
        MyFTPClient ftp = new MyFTPClient();
        ftp.connect(url);
        if (!ftp.setFileType( type )) {
            throw new Exception("Failed to set ftpClient object to BINARY_FILE_TYPE");
        }

        // check for successful connection
        int reply = ftp.getReplyCode();
        if (!FTPReply.isPositiveCompletion(reply)) {
            ftp.disconnect();
            throw new Exception("Failed to connect properly to FTP");
        }

        // attempt login
        if (!ftp.login(user, pass)) {
            String msg = "Failed to login to FTP";
            ftp.disconnect();
            throw new Exception(msg);
        }

        // success! return connected MyFTPClient.
        return ftp;
    }

}

编辑 2:

好的，我遵循了 CheckedXputStream 的建议，这是我的结果.我制作了一个名为 MyFTPClient 的 apache 的 FTPClient 副本，并将 SocketInputStream 和 BufferedInputStream 都包裹在 CheckedInputStream 使用 CRC32 校验和.此外，我包装了我提供给 FTPClient 的 FileOutputStream 以将输出存储在带有 CRC32 校验和的 CheckOutputStream 中.MyFTPClient 的代码发布在 here 我已经修改了上面的测试代码以使用这个版本的 FTPClient(试图将要点 URL 发布到修改后的代码，但我需要 10 个信誉点才能发布多个 URL！)、test.xml 和 test.mp3 以及结果如下:

Okay I followed the CheckedXputStream advice and here are my results. I made a copy of apache's FTPClient called MyFTPClient, and I wrapped both the SocketInputStream and the BufferedInputStream in a CheckedInputStream using CRC32 checksums. Furthermore, I wrapped the FileOutputStream that I give to FTPClient to store the output in a CheckOutputStream with CRC32 checksum. The code for MyFTPClient is posted here and I've modified the above test code to use this version of the FTPClient (tried to post a gist URL to the modified code, but I need 10 reputation points to post more than one URL!), test.xml and test.mp3 and the results were thus:

14:00:08,644 DEBUG [main,TestMain] TEST.XML ASCII
14:00:08,919 DEBUG [main,MyFTPClient] Socket CRC32: 2739864033
14:00:08,919 DEBUG [main,MyFTPClient] Buffer CRC32: 2739864033
14:00:08,954 DEBUG [main,FTPUtils] FileOut CRC32: 866869773

14:00:08,955 DEBUG [main,TestMain] TEST.XML BINARY
14:00:09,270 DEBUG [main,MyFTPClient] Socket CRC32: 2739864033
14:00:09,270 DEBUG [main,MyFTPClient] Buffer CRC32: 2739864033
14:00:09,310 DEBUG [main,FTPUtils] FileOut CRC32: 2739864033

14:00:09,310 DEBUG [main,TestMain] TEST.MP3 ASCII
14:00:10,635 DEBUG [main,MyFTPClient] Socket CRC32: 60615183
14:00:10,635 DEBUG [main,MyFTPClient] Buffer CRC32: 60615183
14:00:10,636 DEBUG [main,FTPUtils] FileOut CRC32: 2352009735

14:00:10,636 DEBUG [main,TestMain] TEST.MP3 BINARY
14:00:11,482 DEBUG [main,MyFTPClient] Socket CRC32: 60615183
14:00:11,482 DEBUG [main,MyFTPClient] Buffer CRC32: 60615183
14:00:11,483 DEBUG [main,FTPUtils] FileOut CRC32: 60615183

这基本上是零意义，因为这里是相应文件的 md5sum:

This makes, basically zero sense whatsoever because here are the md5sums of the corresponsing files:

bf89673ee7ca819961442062eaaf9c3f  ascii/test.mp3
7bd0e8514f1b9ce5ebab91b8daa52c4b  binary/test.mp3
ee172af5ed0204cf9546d176ae00a509  original/test.mp3

104e14b661f3e5dbde494a54334a6dd0  ascii/test.xml
36f482a709130b01d5cddab20a28a8e8  binary/test.xml
104e14b661f3e5dbde494a54334a6dd0  original/test.xml

我很茫然.我发誓在此过程中的任何时候我都没有改变文件名/路径，并且我已经对每个步骤进行了三次检查.它一定很简单，但我不知道下一步该往哪里看.出于实用性的考虑，我将继续调用 shell 进行我的 FTP 传输，但我打算继续这样做，直到我了解到底发生了什么.我会用我的发现更新这个帖子，我会继续感谢任何人可能做出的任何贡献.希望这在某些时候对某人有用！

I'm at a loss. I swear I haven't permuted the filenames/paths at any point in this process, and I've triple-checked every step. It must be something simple, but I haven't the foggiest idea where to look next. In the interest of practicality I'm going to proceed by calling out to the shell to do my FTP transfers, but I intend to pursue this until I understand what the hell is going on. I'll update this thread with my findings, and I'll continue to appreciate any contributions anyone may have. Hopefully this will be useful to someone at some point!

推荐答案

登录ftp服务器后

ftp.setFileType(FTP.BINARY_FILE_TYPE);

下面这行没有解决:

//ftp.setFileTransferMode(org.apache.commons.net.ftp.FTP.BINARY_FILE_TYPE);

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