我在 Windows 7 64 位主机上运行 FreeDos v1.1 VirtualBox 客户机。今天我运行了 mTCP 的 ftpsrv.exe 进行 FTP 访问，并使用 WinSCP 通过 FTP 进入 FreeDos。它从我上次访问的目录启动，即/DRIVE_C/RR2。我浏览到根目录 ( /DRIVE_C) 并上传了一个小文件。文件传输完成后，WinSCP 在文件传输时挂起，然后告诉我连接已断开并且无法检索目录列表：
检测到超时。（数据连接）
无法检索目录列表
列出目录“/DRIVE_C”时出错。
起初我以为是磁盘错误，但文件已成功上传，其他一切似乎都正常。
但是尝试重新连接会导致同样的错误。从 WinSCP 清除远程目录设置无法解决问题。我创建了一个新用户，并以这种方式登录仍然收到相同的错误。
我能要做的是手动指定起始目录几乎/DRIVE_C或之外的任何子目录/DRIVE_C/FDOS。目录随机“未找到”，导致 WinSCP 断开连接，并且 WinSCP 会在传输文件时随机阻塞并断开连接。有时我可以在 FreeDOS 中将文件复制到其他位置，然后通过 FTP 下载，但有时不行。上传文件通常会使其目录对 FTP 不可见。
该虚拟机有一个 2GB 的磁盘，且一半是空的，因此磁盘空间并不不足。
在花了几个小时尝试排除故障后，我终于说“算了”，并安装了 FreeDOS 1.2 VM 客户机。我从 FreeDos 1.1 VM 下载了尽可能多的游戏文件，然后开始将它们上传到我的新 FreeDOS 1.2 VM。我决定将游戏文件放在下面，/DRIVE_C/GAMES/并通过 WinSCP 将它们从主机拖放到客户机。WinSCP 超时并恢复了几次，然后因目录列表错误而卡住，然后因“异常执行”错误而退出。我无法再/DRIVE_C/GAMES/通过 FTP 访问（但直接在系统上工作时没有问题）。
这是我在两个 FreeDOS VM 上的 ftpsrv 用户设置：
# userid password sandbox_directory incoming_directory permissions
redacted redacted [none] [any] all
据此，我的登录信息应该有满的访问不限制。
FreeDOS 1.1 上的 mTCP 配置（大部分为默认设置）
packetint 0x60
mtu 1472
DOSRules
ftpsrv_password_file c:\FDOS\ftppass.txt
ftpsrv_log_file c:\FDOS\ftpsrv.log
ftpsrv_filebuffer_size 16
ftpsrv_tcpbuffer_size 16
ftpsrv_packets_per_roll 2
FreeDOS 1.2 上的 mTCP 配置（大部分为默认设置）
packetint 0x60
mtu 1500
DOSRules
ftpsrv_password_file c:\FDOS\ftppass.txt
ftpsrv_log_file c:\FDOS\ftpsrv.log
# I forgot to uncomment these, but seems to have made no difference
#ftpsrv_filebuffer_size 16
#ftpsrv_tcpbuffer_size 16
#ftpsrv_packets_per_roll 2
我有点怀疑 WinSCP 是不是罪魁祸首，尽管与 mTCP 交互似乎让它变得不稳定。我几乎每天都使用 WinSCP 连接到其他系统，我从未遇到过这种行为。
两个连接的 WinSCP 配置：
Protocol: FTP
Encryption: No encryption
Port number: 21
UTF-8 encoding for filenames: Auto
[ ] Trim VMS version numbers
[ ] Synchronize browsing
[x] Remember last used directory（关闭此功能没有帮助）
[x] Cache visited remote directories
[x] Cache directory changes
[x] Permanent cache
[x] Resolve symbolic links
[ ] Follow symbolic links to directories
[ ] Preserve deleted files to recycle bin
[x] Passive mode
Protocal options: All auto
Server response timeout: 15
Keepalives: Executing dummy protocol commands
Seconds between keepalives: 30
Internet protocol version: Auto
Proxy type: None
我倾向于相信问题出在操作系统权限设置上。但是我在 FreeDos 中找不到有关文件权限的文档。我能找到的最接近的文档是属性，它给了我以下信息（关于 FreeDOS 1.1）：
[D----] FDOS
[----A] KERNAL.SYS
[----A] AUTOEXEC.BAT
[----A] COMMAND.COM
[----A] FDCONFIG.SYS
[----A] BOOTSECT.BIN
[D----] DUKE3D
[D----] RR2
这显然与权限无关。
更新2017.04.03：根据要求，以下是我的日志文件。（WinSCP 没有记录日志，因此这是来自这早晨。）
WinSCP 的日志文件：
. 2017-04-03 10:22:22.641 --------------------------------------------------------------------------
. 2017-04-03 10:22:22.642 WinSCP Version 5.9.4 (Build 7333) (OS 6.1.7601 Service Pack 1 - Windows 7 Professional)
. 2017-04-03 10:22:22.643 Configuration: C:\Users\Redacted\AppData\Roaming\winscp.ini
. 2017-04-03 10:22:22.643 Log level: Normal
. 2017-04-03 10:22:22.643 Local account: Redacted
. 2017-04-03 10:22:22.644 Working directory: C:\Users\Redacted
. 2017-04-03 10:22:22.644 Process ID: 7508
. 2017-04-03 10:22:22.644 Command-line: "C:\Windows\winscp.exe"
. 2017-04-03 10:22:22.644 Time zone: Current: GMT-6, Standard: GMT-7 (Mountain Standard Time), DST: GMT-6 (Mountain Daylight Time), DST Start: 3/12/2017, DST End: 11/5/2017
. 2017-04-03 10:22:22.644 Login time: Monday, April 03, 2017 10:22:22 AM
. 2017-04-03 10:22:22.644 --------------------------------------------------------------------------
. 2017-04-03 10:22:22.644 Session name: FreeDos 1.1 (Modified site)
. 2017-04-03 10:22:22.644 Host name: 192.168.1.123 (Port: 21)
. 2017-04-03 10:22:22.644 User name: redacted (Password: No, Key file: No, Passphrase: No)
. 2017-04-03 10:22:22.644 Transfer Protocol: FTP
. 2017-04-03 10:22:22.644 Ping type: Dummy, Ping interval: 30 sec; Timeout: 5 sec
. 2017-04-03 10:22:22.644 Disable Nagle: No
. 2017-04-03 10:22:22.644 Proxy: None
. 2017-04-03 10:22:22.644 Send buffer: 262144
. 2017-04-03 10:22:22.644 UTF: Auto
. 2017-04-03 10:22:22.644 FTPS: None [Client certificate: No]
. 2017-04-03 10:22:22.645 FTP: Passive: Yes [Force IP: Auto]; MLSD: Auto [List all: Auto]; HOST: Auto
. 2017-04-03 10:22:22.645 Local directory: C:\TEMP\FdDOS, Remote directory: /DRIVE_C/UP, Update: Yes, Cache: Yes
. 2017-04-03 10:22:22.645 Cache directory changes: Yes, Permanent: Yes
. 2017-04-03 10:22:22.645 Recycle bin: Delete to: No, Overwritten to: No, Bin path:
. 2017-04-03 10:22:22.645 Timezone offset: 0h 0m
. 2017-04-03 10:22:22.645 --------------------------------------------------------------------------
. 2017-04-03 10:22:22.774 Connecting to 192.168.1.123 ...
. 2017-04-03 10:22:22.774 Connected with 192.168.1.123. Waiting for welcome message...
< 2017-04-03 10:22:22.774 220 mTCP FTP Server
> 2017-04-03 10:22:22.774 USER redacted
< 2017-04-03 10:22:22.775 331 User OK, send Password
> 2017-04-03 10:22:26.075 PASS ********
< 2017-04-03 10:22:26.281 230 User logged in
> 2017-04-03 10:22:26.281 SYST
< 2017-04-03 10:22:26.281 215 UNIX Type: L8
> 2017-04-03 10:22:26.281 FEAT
< 2017-04-03 10:22:26.282 211-mTCP FTP server features:
< 2017-04-03 10:22:26.282 MDTM
< 2017-04-03 10:22:26.282 211 End
. 2017-04-03 10:22:26.327 Connected
. 2017-04-03 10:22:26.327 --------------------------------------------------------------------------
. 2017-04-03 10:22:26.327 Using FTP protocol.
. 2017-04-03 10:22:26.329 Doing startup conversation with host.
> 2017-04-03 10:22:26.379 PWD
< 2017-04-03 10:22:26.380 257 "/" is current directory
. 2017-04-03 10:22:26.380 Changing directory to "/DRIVE_C/UP".
> 2017-04-03 10:22:26.380 CWD /DRIVE_C/UP
< 2017-04-03 10:22:26.381 250 CWD command successful
. 2017-04-03 10:22:26.381 Getting current directory name.
> 2017-04-03 10:22:26.381 PWD
< 2017-04-03 10:22:26.381 257 "/DRIVE_C/UP/" is current directory
. 2017-04-03 10:22:26.581 Retrieving directory listing...
> 2017-04-03 10:22:26.581 TYPE A
< 2017-04-03 10:22:26.581 200 Type set to A
> 2017-04-03 10:22:26.582 PASV
< 2017-04-03 10:22:26.582 227 Entering Passive Mode (192,168,1,123,8,42)
> 2017-04-03 10:22:26.582 LIST -a
. 2017-04-03 10:22:26.582 Connecting to 192.168.1.123:2090 ...
< 2017-04-03 10:22:26.583 150 Sending file list
. 2017-04-03 10:22:26.583 Data connection closed
. 2017-04-03 10:22:26.583 <Empty directory listing>
< 2017-04-03 10:22:26.584 226 Transfer complete
. 2017-04-03 10:22:26.584 Directory listing successful
. 2017-04-03 10:22:26.584 LIST with -a switch returned empty directory listing, will try pure LIST
. 2017-04-03 10:22:26.584 Retrieving directory listing...
> 2017-04-03 10:22:26.584 TYPE A
< 2017-04-03 10:22:26.584 200 Type set to A
> 2017-04-03 10:22:26.585 PASV
< 2017-04-03 10:22:26.585 227 Entering Passive Mode (192,168,1,123,8,91)
> 2017-04-03 10:22:26.585 LIST
. 2017-04-03 10:22:26.585 Connecting to 192.168.1.123:2139 ...
< 2017-04-03 10:22:26.586 150 Sending file list
. 2017-04-03 10:22:26.586 Data connection closed
. 2017-04-03 10:22:26.586 <Empty directory listing>
< 2017-04-03 10:22:26.586 226 Transfer complete
. 2017-04-03 10:22:26.586 Directory listing successful
. 2017-04-03 10:22:26.587 ..;D;0;1899-12-30T07:00:00.000Z;0;"" [0];"" [0];---------;0
. 2017-04-03 10:22:26.681 Startup conversation with host finished.
. 2017-04-03 10:22:30.251 Cached directory change via ".." to "/DRIVE_C".
. 2017-04-03 10:22:30.251 Getting current directory name.
. 2017-04-03 10:22:30.254 Retrieving directory listing...
> 2017-04-03 10:22:30.254 CWD /DRIVE_C/
< 2017-04-03 10:22:30.254 250 CWD command successful
> 2017-04-03 10:22:30.254 PWD
< 2017-04-03 10:22:30.254 257 "/DRIVE_C/" is current directory
> 2017-04-03 10:22:30.254 TYPE A
< 2017-04-03 10:22:30.254 200 Type set to A
> 2017-04-03 10:22:30.254 PASV
< 2017-04-03 10:22:30.254 227 Entering Passive Mode (192,168,1,123,11,61)
> 2017-04-03 10:22:30.254 LIST
. 2017-04-03 10:22:30.254 Connecting to 192.168.1.123:2877 ...
< 2017-04-03 10:22:30.256 150 Sending file list
. 2017-04-03 10:22:30.256 Data connection closed
< 2017-04-03 10:22:30.256 226 Transfer complete
. 2017-04-03 10:22:30.256 drwxrwxrwx 1 ftp ftp 0 Jul 14 2016 FDOS
. 2017-04-03 10:22:30.256 -rwxrwxrwx 1 ftp ftp 45344 Jun 21 2011 KERNEL.SYS
. 2017-04-03 10:22:30.256 -rwxrwxrwx 1 ftp ftp 1266 Apr 2 06:26 AUTOEXEC.BAT
. 2017-04-03 10:22:30.256 -rwxrwxrwx 1 ftp ftp 66945 Aug 28 2006 COMMAND.COM
. 2017-04-03 10:22:30.256 -rwxrwxrwx 1 ftp ftp 848 Jul 14 2016 FDCONFIG.SYS
. 2017-04-03 10:22:30.256 -rwxrwxrwx 1 ftp ftp 512 Jul 14 2016 BOOTSECT.BIN
. 2017-04-03 10:22:30.256 drwxrwxrwx 1 ftp ftp 0 Jul 14 2016 RR
. 2017-04-03 10:22:30.256 drwxrwxrwx 1 ftp ftp 0 Jul 14 2016 ATOMIC
. 2017-04-03 10:22:30.256 drwxrwxrwx 1 ftp ftp 0 Jul 14 2016 DUKE3D
. 2017-04-03 10:22:30.256 drwxrwxrwx 1 ftp ftp 0 Jul 30 2016 RR2
. 2017-04-03 10:22:30.256 drwxrwxrwx 1 ftp ftp 0 Aug 9 2016 HUNT
. 2017-04-03 10:22:30.256 drwxrwxrwx 1 ftp ftp 0 Apr 2 08:13 TEST
. 2017-04-03 10:22:30.256 -rwxrwxrwx 1 ftp ftp 527 Apr 2 07:09 README.TXT
. 2017-04-03 10:22:30.256 drwxrwxrwx 1 ftp ftp 0 Apr 2 18:23 DCINST
. 2017-04-03 10:22:30.256 drwxrwxrwx 1 ftp ftp 0 Apr 2 18:26 DUKEDC
. 2017-04-03 10:22:30.256 drwxrwxrwx 1 ftp ftp 0 Apr 2 18:36 ERR200
. 2017-04-03 10:22:30.256 drwxrwxrwx 1 ftp ftp 0 Apr 2 18:39 UP
. 2017-04-03 10:22:30.256 -rwxrwxrwx 1 ftp ftp 161 Apr 2 18:44 GAMER.INI
. 2017-04-03 10:22:30.266 Directory listing successful
. 2017-04-03 10:22:30.266 ..;D;0;1899-12-30T07:00:00.000Z;0;"" [0];"" [0];---------;0
. 2017-04-03 10:22:30.266 FDOS;D;0;2016-07-14T06:00:00.000Z;2;"ftp" [0];"ftp" [0];rwxrwxrwx;1
. 2017-04-03 10:22:30.266 KERNEL.SYS;-;45344;2011-06-21T06:00:00.000Z;2;"ftp" [0];"ftp" [0];rwxrwxrwx;1
. 2017-04-03 10:22:30.266 AUTOEXEC.BAT;-;1266;2017-04-02T12:26:00.000Z;1;"ftp" [0];"ftp" [0];rwxrwxrwx;1
. 2017-04-03 10:22:30.266 COMMAND.COM;-;66945;2006-08-28T06:00:00.000Z;2;"ftp" [0];"ftp" [0];rwxrwxrwx;1
. 2017-04-03 10:22:30.266 FDCONFIG.SYS;-;848;2016-07-14T06:00:00.000Z;2;"ftp" [0];"ftp" [0];rwxrwxrwx;1
. 2017-04-03 10:22:30.266 BOOTSECT.BIN;-;512;2016-07-14T06:00:00.000Z;2;"ftp" [0];"ftp" [0];rwxrwxrwx;1
. 2017-04-03 10:22:30.267 RR;D;0;2016-07-14T06:00:00.000Z;2;"ftp" [0];"ftp" [0];rwxrwxrwx;1
. 2017-04-03 10:22:30.267 ATOMIC;D;0;2016-07-14T06:00:00.000Z;2;"ftp" [0];"ftp" [0];rwxrwxrwx;1
. 2017-04-03 10:22:30.267 DUKE3D;D;0;2016-07-14T06:00:00.000Z;2;"ftp" [0];"ftp" [0];rwxrwxrwx;1
. 2017-04-03 10:22:30.267 RR2;D;0;2016-07-30T06:00:00.000Z;2;"ftp" [0];"ftp" [0];rwxrwxrwx;1
. 2017-04-03 10:22:30.267 HUNT;D;0;2016-08-09T06:00:00.000Z;2;"ftp" [0];"ftp" [0];rwxrwxrwx;1
. 2017-04-03 10:22:30.267 TEST;D;0;2017-04-02T14:13:00.000Z;1;"ftp" [0];"ftp" [0];rwxrwxrwx;1
. 2017-04-03 10:22:30.267 README.TXT;-;527;2017-04-02T13:09:00.000Z;1;"ftp" [0];"ftp" [0];rwxrwxrwx;1
. 2017-04-03 10:22:30.267 DCINST;D;0;2017-04-03T00:23:00.000Z;1;"ftp" [0];"ftp" [0];rwxrwxrwx;1
. 2017-04-03 10:22:30.267 DUKEDC;D;0;2017-04-03T00:26:00.000Z;1;"ftp" [0];"ftp" [0];rwxrwxrwx;1
. 2017-04-03 10:22:30.267 ERR200;D;0;2017-04-03T00:36:00.000Z;1;"ftp" [0];"ftp" [0];rwxrwxrwx;1
. 2017-04-03 10:22:30.267 UP;D;0;2017-04-03T00:39:00.000Z;1;"ftp" [0];"ftp" [0];rwxrwxrwx;1
. 2017-04-03 10:22:30.267 GAMER.INI;-;161;2017-04-03T00:44:00.000Z;1;"ftp" [0];"ftp" [0];rwxrwxrwx;1
. 2017-04-03 10:22:34.312 Cached directory change via "FDOS" to "/DRIVE_C/FDOS".
. 2017-04-03 10:22:34.312 Getting current directory name.
. 2017-04-03 10:22:34.316 Retrieving directory listing...
> 2017-04-03 10:22:34.316 CWD /DRIVE_C/FDOS/
< 2017-04-03 10:22:34.317 250 CWD command successful
> 2017-04-03 10:22:34.317 PWD
< 2017-04-03 10:22:34.317 257 "/DRIVE_C/FDOS/" is current directory
> 2017-04-03 10:22:34.317 TYPE A
< 2017-04-03 10:22:34.317 200 Type set to A
> 2017-04-03 10:22:34.317 PASV
< 2017-04-03 10:22:34.317 227 Entering Passive Mode (192,168,1,123,9,182)
> 2017-04-03 10:22:34.317 LIST
. 2017-04-03 10:22:34.317 Connecting to 192.168.1.123:2486 ...
< 2017-04-03 10:22:34.317 150 Sending file list
< 2017-04-03 10:22:34.317 226 Transfer complete
. 2017-04-03 10:22:39.872 Timeout detected. (data connection)
. 2017-04-03 10:22:39.872 Could not retrieve directory listing
. 2017-04-03 10:22:39.872 Connection was lost, asking what to do.
. 2017-04-03 10:22:39.872 Asking user:
. 2017-04-03 10:22:39.872 Lost connection. ("Timeout detected. (data connection)","Could not retrieve directory listing")
* 2017-04-03 10:22:41.881 (ESshFatal) **Lost connection.**
* 2017-04-03 10:22:41.881 Timeout detected. (data connection)
* 2017-04-03 10:22:41.881 Could not retrieve directory listing
* 2017-04-03 10:22:41.881 Error listing directory '/DRIVE_C/FDOS'.
* 2017-04-03 10:22:41.881 Error changing directory to 'FDOS'.
FreeDOS 1.1 上的 mTCP 日志文件
2017-04-03 10:17:37.40 mTCP FtpSrv version (Oct 29 2011) starting
2017-04-03 10:17:37.40 Clients: 3, Client file buffer size: 16384, TCP buffer size: 16384
2017-04-03 10:17:37.40 Packets per poll: 2, TCP sockets: 10, Send buffers: 15, Recv buffers: 40
2017-04-03 10:17:37.40 Client session timeout: 182 seconds
2017-04-03 10:17:37.40 Control port: 21, Pasv ports: 2048-3071
2017-04-03 10:17:37.46 Real IP address: 192.168.1.123, Pasv response IP addr: 192.168.1.123
2017-04-03 10:17:49.65 (0) User redacted signed in from 192.168.1.147:51304 at 2017-04-03 10:17:44
2017-04-03 10:18:09.31 (0) Disconnect: 192.168.1.147:51304
2017-04-03 10:22:23.84 (1) User redacted signed in from 192.168.1.147:51316 at 2017-04-03 10:22:20
2017-04-03 10:22:37.62 (1) Disconnect: 192.168.1.147:51316
2017-04-03 10:36:36.83 (2) User redacted signed in from 192.168.1.147:51365 at 2017-04-03 10:36:33
2017-04-03 10:36:51.39 (2) Disconnect: 192.168.1.147:51365
2017-04-03 10:36:55.83 Shutdown requested
2017-04-03 10:36:56.88 Stats: Sessions: 3 Timeouts: 0
2017-04-03 10:36:56.88 LIST: 11 NLST: 0 RETR: 0
2017-04-03 10:36:56.88 STOR: 0 STOU: 0 APPE: 0
2017-04-03 10:36:56.88 === Server shutdown ===
更新： 我尝试使用 Core FTP，这是它的日志：
Welcome to Core FTP, release ver 2.2, build 1887 (x64) -- © 2003-2016
WinSock 2.0
Mem -- 33,531,236 KB, Virt -- 8,589,934,464 KB
Started on Monday April 03, 2017 at 11:36:AM
Connect socket #752 to 192.168.1.123, port 21...220 mTCP FTP Server
USER redacted
331 User OK, send Password
PASS **********
230 User logged in
SYST
215 UNIX Type: L8
Keep alive off...PWD
257 "/" is current directory
PASV
227 Entering Passive Mode (192,168,1,123,10,76)
LIST
Connect socket #800 to 192.168.1.123, port 2636...150 Sending file list
226 Transfer complete
Transferred 54 bytes in 60.000 seconds
CWD /DRIVE_C
250 CWD command successful
PASV
227 Entering Passive Mode (192,168,1,123,9,147)
LIST
Connect socket #844 to 192.168.1.123, port 2451...150 Sending file list
226 Transfer complete
Transferred 1,028 bytes in 60.001 seconds
CWD /DRIVE_C/FDOS/
250 CWD command successful
PASV
227 Entering Passive Mode (192,168,1,123,8,41)
LIST
Connect socket #960 to 192.168.1.123, port 2089...150 Sending file list
226 Transfer complete
Transferred 1,279 bytes in 0.001 seconds
CDUP
250 CWD command successful
PWD
257 "/DRIVE_C/" is current directory
PASV
227 Entering Passive Mode (192,168,1,123,8,67)
LIST
Connect socket #972 to 192.168.1.123, port 2115...150 Sending file list
226 Transfer complete
Transferred 1,028 bytes in 60.001 seconds
QUIT
221 Server closing connection
Total uploaded files: 0
Total uploaded data: 0
Total downloaded files: 0
Total downloaded data: 0
如您所见，检索 54 字节的目录信息仅花费了 60 多秒。Core FTP 似乎更成功，因为它最终获取目录列表。 有时它的运行速度就像您期望的 FTP 一样快，比如它在 0.001 秒内传输了 1,279 个字节，但它似乎仍然时好时坏。
我想也许我只是没有让 WinSCP 等待足够长的时间，所以我将超时时间增加到两分钟。唯一不同的行为是 WinSCP 挂起整整两分钟后才显示错误。
这最近两次尝试的 mTCP 日志只显示“用户已登录”和“断开连接”，超时 0 次且无错误，就像本页上方的完整日志一样。
我开始认为问题可能出在路由器上，于是我关闭路由器然后重新打开，但结果并没有什么不同。我的电脑通过 3 英尺长的电线直接连接到路由器，其他互联网使用情况似乎都很正常，所以我不太可能遇到网络干扰。
也许我该向 mTCP 的开发人员提交一个错误，看看他能想出什么办法。