.net - 为什么我不会从 FTP 服务器得到响应？
问题描述
不久前，我创建了一个应用程序，它利用 FluentFTP 从 FTP 服务器列出和下载文件。在过去一个月内，每当使用该库执行任何 FTP 操作时，该应用程序都会开始超时。我检查了 FluentFTP 生成的日志，操作已成功执行，但未正确处理。我尝试了 GetListing 和 Download 并遇到了同样的错误。查看堆栈跟踪，常见的故障点似乎发生在GetReply()源代码中：
从服务器检索回复。除非您确定已发送回复，即您执行了命令，否则请勿执行此方法。这样做会导致代码无限期地挂起，等待永远不会到来的服务器回复。
在我看来，由于某种原因，我没有得到 FTP 服务器的响应。但是，我不知道为什么。我可以毫无问题地使用像 WinSCP 这样的独立 FTP 客户端。准系统 .NET FtpWebRequest 和 FtpWebResponse 也可以工作。我尝试在家里测试，它工作正常。我咨询了我的 IT 部门，他们声称他们最近没有进行任何更改。我没有更改我的代码。无论我连接到哪个服务器，都会发生这种情况。
任何帮助将不胜感激。
这是我的测试代码。（我在 vanilla .NET 下运行此程序。超时也发生在 .NET core 下，只是没有引发任何异常）：
private static void ListViaFluentFtp()
{
FtpTrace.AddListener(new ConsoleTraceListener());
var ftpClient = new FtpClient("test.rebex.net", "demo", "password");
ftpClient.Connect();
ftpClient.GetListing("/"); //TimeOutException here
}
这是 FleuntFTP 生成的日志：
# Connect()
Status: Connecting to 195.144.107.198:21
Response: 220 Microsoft FTP Service
Status: Detected FTP server: WindowsServerIIS
Command: USER demo
Response: 331 Password required for demo.
Command: PASS ***
Response: 230 User logged in.
Command: FEAT
Response: 211-Extended features supported:
Response: LANG EN*
Response: UTF8
Response: AUTH TLS;TLS-C;SSL;TLS-P;
Response: PBSZ
Response: PROT C;P;
Response: CCC
Response: HOST
Response: SIZE
Response: MDTM
Response: REST STREAM
Response: 211 END
Status: Text encoding: System.Text.UTF8Encoding
Command: OPTS UTF8 ON
Response: 200 OPTS UTF8 command successful - UTF8 encoding now ON.
Command: SYST
Response: 215 Windows_NT
# GetListing("/", Auto)
Command: TYPE I
Response: 200 Type set to I.
# OpenPassiveDataStream(AutoPassive, "LIST /", 0)
Command: EPSV
Response: 229 Entering Extended Passive Mode (|||1033|)
Status: Connecting to 195.144.107.198:1033
Command: LIST /
Response: 125 Data connection already open; Transfer starting.
+---------------------------------------+
Listing: 10-27-15 03:46PM <DIR> pub
Listing: 04-08-14 03:09PM 403 readme.txt
-----------------------------------------
Status: Disposing FtpSocketStream...
# CloseDataStream()
The thread 0x5b4 has exited with code 0 (0x0).
Status: Disposing FtpSocketStream...
Exception thrown: 'System.TimeoutException' in FluentFTP.dll
An unhandled exception of type 'System.TimeoutException' occurred in FluentFTP.dll
Timed out trying to read data from the socket stream!
这是堆栈跟踪：
System.TimeoutException
HResult=0x80131505
Message=Timed out trying to read data from the socket stream!
Source=FluentFTP
StackTrace:
at FluentFTP.FtpSocketStream.Read(Byte[] buffer, Int32 offset, Int32 count)
at FluentFTP.FtpSocketStream.ReadLine(Encoding encoding)
at FluentFTP.FtpClient.GetReply()
at FluentFTP.FtpClient.CloseDataStream(FtpDataStream stream)
at FluentFTP.FtpDataStream.Close()
at FluentFTP.FtpClient.GetListingInternal(String listcmd, FtpListOption options, Boolean retry)
at FluentFTP.FtpClient.GetListing(String path, FtpListOption options)
at FluentFTP.FtpClient.GetListing(String path)
at FtPNetTest.Program.Main(String[] args) in C:\Users\jevensen\source\repos\FtpTest\FtPNetTest\Program.cs:line 18
这是下载的日志（这是在有效忽略超时的最新更新之前）：
# Connect()
Status: Connecting to 195.144.107.198:21
Response: 220 Microsoft FTP Service
Status: Detected FTP server: WindowsServerIIS
Command: USER demo
Response: 331 Password required for demo.
Command: PASS ***
Response: 230 User logged in.
Command: FEAT
Response: 211-Extended features supported:
Response: LANG EN*
Response: UTF8
Response: AUTH TLS;TLS-C;SSL;TLS-P;
Response: PBSZ
Response: PROT C;P;
Response: CCC
Response: HOST
Response: SIZE
Response: MDTM
Response: REST STREAM
Response: 211 END
Status: Text encoding: System.Text.UTF8Encoding
Command: OPTS UTF8 ON
Response: 200 OPTS UTF8 command successful - UTF8 encoding now ON.
Command: SYST
Response: 215 Windows_NT
# Download("/readme.txt")
# OpenRead("/readme.txt", Binary, 0)
Command: TYPE I
Response: 200 Type set to I.
# OpenPassiveDataStream(AutoPassive, "RETR /readme.txt", 0)
Command: EPSV
Response: 229 Entering Extended Passive Mode (|||1027|)
Status: Connecting to 195.144.107.198:1027
Command: RETR /readme.txt
Response: 125 Data connection already open; Transfer starting.
Status: Disposing FtpSocketStream...
The thread 0x4830 has exited with code 0 (0x0).
The thread 0x3f88 has exited with code 0 (0x0).
The thread 0x4c20 has exited with code 0 (0x0).
Status: Disposing FtpSocketStream...
Status: Disposing FtpSocketStream...
Exception thrown: 'FluentFTP.FtpException' in FluentFTP.dll
An unhandled exception of type 'FluentFTP.FtpException' occurred in FluentFTP.dll
Error while downloading the file from the server. See InnerException for more info.
堆栈跟踪：
This exception was originally thrown at this call stack:
FluentFTP.FtpSocketStream.Read(byte[], int, int)
FluentFTP.FtpSocketStream.ReadLine(System.Text.Encoding)
FluentFTP.FtpClient.GetReply()
FluentFTP.FtpClient.DownloadFileInternal(string, System.IO.Stream, long, System.Action<FluentFTP.FtpProgress>)
编辑：这是来自 WinSCP 的 1 级日志做同样的事情：
. 2020-01-23 08:55:54.627 --------------------------------------------------------------------------
. 2020-01-23 08:55:54.628 WinSCP Version 5.13 (Build 8172) (OS 10.0.18362 - Windows 10 Enterprise)
. 2020-01-23 08:55:54.629 Configuration: C:\Users\***\Downloads\WinSCP\WinSCP.ini
. 2020-01-23 08:55:54.629 Log level: Debug 1
. 2020-01-23 08:55:54.629 Local account: OFFICE\***
. 2020-01-23 08:55:54.629 Working directory: C:\Users\***\Downloads\WinSCP
. 2020-01-23 08:55:54.629 Process ID: 5352
. 2020-01-23 08:55:54.631 Command-line: "C:\Users\***\Downloads\WinSCP\WinSCP.exe"
. 2020-01-23 08:55:54.639 Time zone: Current: GMT-8, Standard: GMT-8 (Pacific Standard Time), DST: GMT-7 (Pacific Daylight Time), DST Start: 3/8/2020, DST End: 11/1/2020
. 2020-01-23 08:55:54.639 Login time: Thursday, January 23, 2020 8:55:54 AM
. 2020-01-23 08:55:54.639 --------------------------------------------------------------------------
. 2020-01-23 08:55:54.640 Session name: demo@test.rebex.net (Ad-Hoc site)
. 2020-01-23 08:55:54.640 Host name: test.rebex.net (Port: 21)
. 2020-01-23 08:55:54.640 User name: demo (Password: Yes, Key file: No, Passphrase: No)
. 2020-01-23 08:55:54.640 Transfer Protocol: FTP
. 2020-01-23 08:55:54.640 Ping type: Dummy, Ping interval: 30 sec; Timeout: 15 sec
. 2020-01-23 08:55:54.640 Disable Nagle: No
. 2020-01-23 08:55:54.640 Proxy: None
. 2020-01-23 08:55:54.640 Send buffer: 262144
. 2020-01-23 08:55:54.640 UTF: Auto
. 2020-01-23 08:55:54.640 FTPS: None [Client certificate: No]
. 2020-01-23 08:55:54.640 FTP: Passive: Yes [Force IP: Auto]; MLSD: Auto [List all: Auto]; HOST: Auto
. 2020-01-23 08:55:54.640 Local directory: default, Remote directory: home, Update: Yes, Cache: Yes
. 2020-01-23 08:55:54.640 Cache directory changes: Yes, Permanent: Yes
. 2020-01-23 08:55:54.640 Recycle bin: Delete to: No, Overwritten to: No, Bin path:
. 2020-01-23 08:55:54.640 Timezone offset: 0h 0m
. 2020-01-23 08:55:54.640 --------------------------------------------------------------------------
. 2020-01-23 08:55:54.757 Session upkeep
. 2020-01-23 08:55:54.897 Connecting to test.rebex.net ...
. 2020-01-23 08:55:54.963 Connected with test.rebex.net. Waiting for welcome message...
< 2020-01-23 08:55:55.299 220 Microsoft FTP Service
> 2020-01-23 08:55:55.299 USER demo
< 2020-01-23 08:55:55.468 331 Password required for demo.
> 2020-01-23 08:55:55.468 PASS ********
< 2020-01-23 08:55:55.635 230 User logged in.
> 2020-01-23 08:55:55.636 SYST
. 2020-01-23 08:55:55.804 The server is probably running Windows, assuming that directory listing timestamps are affected by DST.
< 2020-01-23 08:55:55.804 215 Windows_NT
> 2020-01-23 08:55:55.804 FEAT
< 2020-01-23 08:55:55.970 211-Extended features supported:
< 2020-01-23 08:55:55.970 LANG EN*
< 2020-01-23 08:55:55.970 UTF8
< 2020-01-23 08:55:55.970 AUTH TLS;TLS-C;SSL;TLS-P;
< 2020-01-23 08:55:55.970 PBSZ
< 2020-01-23 08:55:55.970 PROT C;P;
< 2020-01-23 08:55:55.970 CCC
< 2020-01-23 08:55:55.970 HOST
< 2020-01-23 08:55:55.970 SIZE
< 2020-01-23 08:55:55.973 MDTM
< 2020-01-23 08:55:55.973 REST STREAM
< 2020-01-23 08:55:55.973 211 END
> 2020-01-23 08:55:55.973 OPTS UTF8 ON
< 2020-01-23 08:55:56.140 200 OPTS UTF8 command successful - UTF8 encoding now ON.
. 2020-01-23 08:55:56.140 Session upkeep
. 2020-01-23 08:55:56.193 Connected
. 2020-01-23 08:55:56.193 Got reply 1 to the command 1
. 2020-01-23 08:55:56.193 --------------------------------------------------------------------------
. 2020-01-23 08:55:56.193 Using FTP protocol.
. 2020-01-23 08:55:56.197 Doing startup conversation with host.
. 2020-01-23 08:55:56.197 Session upkeep
> 2020-01-23 08:55:56.207 PWD
< 2020-01-23 08:55:56.373 257 "/" is current directory.
. 2020-01-23 08:55:56.373 Got reply 1 to the command 16
. 2020-01-23 08:55:56.373 Getting current directory name.
. 2020-01-23 08:55:56.440 Retrieving directory listing...
> 2020-01-23 08:55:56.440 TYPE A
< 2020-01-23 08:55:56.607 200 Type set to A.
> 2020-01-23 08:55:56.612 PASV
< 2020-01-23 08:55:56.781 227 Entering Passive Mode (195,144,107,198,4,10).
> 2020-01-23 08:55:56.781 LIST -a
. 2020-01-23 08:55:56.781 Connecting to 195.144.107.198:1034 ...
< 2020-01-23 08:55:56.952 150 Opening ASCII mode data connection.
. 2020-01-23 08:55:57.119 Data connection closed
. 2020-01-23 08:55:57.119 12-03-15 08:14PM <DIR> aspnet_client
. 2020-01-23 08:55:57.119 10-27-15 03:46PM <DIR> pub
. 2020-01-23 08:55:57.119 04-08-14 03:09PM 403 readme.txt
< 2020-01-23 08:55:57.119 226 Transfer complete.
. 2020-01-23 08:55:57.119 Directory listing successful
. 2020-01-23 08:55:57.122 Got reply 1 to the command 2
. 2020-01-23 08:55:57.122 Detecting timezone difference...
. 2020-01-23 08:55:57.122 Retrieving file information...
> 2020-01-23 08:55:57.122 PWD
< 2020-01-23 08:55:57.310 257 "/" is current directory.
> 2020-01-23 08:55:57.310 CWD /readme.txt
< 2020-01-23 08:55:57.481 550 The filename, directory name, or volume label syntax is incorrect.
> 2020-01-23 08:55:57.481 TYPE I
< 2020-01-23 08:55:57.646 200 Type set to I.
> 2020-01-23 08:55:57.646 SIZE /readme.txt
< 2020-01-23 08:55:57.814 213 403
> 2020-01-23 08:55:57.814 MDTM /readme.txt
< 2020-01-23 08:55:57.980 213 20140408140939
. 2020-01-23 08:55:57.980 Retrieving file information successful
. 2020-01-23 08:55:57.980 Got reply 1 to the command 1024
. 2020-01-23 08:55:57.983 Timezone difference of +9 detected using file /readme.txt (Listing: 2014-04-08T23:09:00.000Z, UTF: 2014-04-08T14:09:00.000Z)
. 2020-01-23 08:55:57.984 ..;D;0;1899-12-30T08:00:00.000Z;0;"" [0];"" [0];---------;0
. 2020-01-23 08:55:57.984 aspnet_client;D;0;2015-12-03T19:14:00.000Z;1;"" [0];"" [0];---------;0
. 2020-01-23 08:55:57.984 pub;D;0;2015-10-27T14:46:00.000Z;1;"" [0];"" [0];---------;0
. 2020-01-23 08:55:57.984 readme.txt;-;403;2014-04-08T14:09:00.000Z;1;"" [0];"" [0];---------;0
. 2020-01-23 08:55:57.984 Session upkeep
. 2020-01-23 08:55:58.012 Startup conversation with host finished.
. 2020-01-23 08:55:58.156 Session upkeep
. 2020-01-23 08:55:58.658 Session upkeep
. 2020-01-23 08:55:59.158 Session upkeep
. 2020-01-23 08:55:59.656 Session upkeep
. 2020-01-23 08:56:00.157 Session upkeep
. 2020-01-23 08:56:00.612 Copying 1 files/directories to local directory "C:\Users\***\Documents\" - total size: 403
. 2020-01-23 08:56:00.612 PrTime: Yes; PrRO: No; Rght: rw-r--r--; PrR: No (No); FnCs: N; RIC: 0100; Resume: S (102400); CalcS: Yes; Mask: *.*
. 2020-01-23 08:56:00.612 TM: B; ClAr: No; RemEOF: No; RemBOM: No; CPS: 0; NewerOnly: No; InclM: ; ResumeL: 0
. 2020-01-23 08:56:00.612 AscM: *.*html; *.htm; *.txt; *.php; *.php3; *.cgi; *.c; *.cpp; *.h; *.pas; *.bas; *.tex; *.pl; *.js; .htaccess; *.xtml; *.css; *.cfg; *.ini; *.sh; *.xml
. 2020-01-23 08:56:00.615 File: '/readme.txt' [2014-04-08T14:09:00.000Z] [403]
. 2020-01-23 08:56:00.655 Copying "/readme.txt" to local directory started.
. 2020-01-23 08:56:00.655 Binary transfer mode selected.
. 2020-01-23 08:56:00.655 Starting download of /readme.txt
. 2020-01-23 08:56:00.656 Asking user:
. 2020-01-23 08:56:00.656 **Overwrite local file 'readme.txt'?**
. 2020-01-23 08:56:00.656
. 2020-01-23 08:56:00.656 Destination directory already contains file 'readme.txt'.
. 2020-01-23 08:56:00.656 Choose, if you want to overwrite the file or skip this transfer and keep existing file.
. 2020-01-23 08:56:00.656
. 2020-01-23 08:56:00.656 New: 403 bytes, 4/8/2014 7:09 AM
. 2020-01-23 08:56:00.656 Existing: 403 bytes, 4/8/2014 7:09:39 AM ()
. 2020-01-23 08:56:01.161 Session upkeep
. 2020-01-23 08:56:01.658 Session upkeep
. 2020-01-23 08:56:01.908 Transfer progress: Transferred: 0, Left: 0:00:00, CPS: 0/s
> 2020-01-23 08:56:01.911 TYPE I
< 2020-01-23 08:56:02.079 200 Type set to I.
> 2020-01-23 08:56:02.079 PASV
< 2020-01-23 08:56:02.245 227 Entering Passive Mode (195,144,107,198,4,6).
> 2020-01-23 08:56:02.245 RETR readme.txt
. 2020-01-23 08:56:02.245 Connecting to 195.144.107.198:1030 ...
< 2020-01-23 08:56:02.597 150 Opening BINARY mode data connection.
. 2020-01-23 08:56:02.746 Data connection closed
< 2020-01-23 08:56:02.746 226 Transfer complete.
. 2020-01-23 08:56:02.747 Preserving timestamp [2014-04-08T14:09:00.000Z]
. 2020-01-23 08:56:02.747 Download successful
. 2020-01-23 08:56:02.747 Got reply 1 to the command 4
. 2020-01-23 08:56:02.748 Transfer done: '/readme.txt' => 'C:\Users\***\Documents\readme.txt' [403]
. 2020-01-23 08:56:02.748 Copying finished: Transferred: 403, Elapsed: 0:00:02, CPS: 2,583/s
. 2020-01-23 08:56:03.163 Session upkeep
. 2020-01-23 08:56:03.660 Session upkeep
. 2020-01-23 08:56:04.156 Session upkeep
. 2020-01-23 08:56:04.654 Session upkeep
. 2020-01-23 08:56:05.157 Session upkeep
. 2020-01-23 08:56:05.661 Session upkeep
. 2020-01-23 08:56:06.174 Got reply 1004 to the command 4
. 2020-01-23 08:56:06.174 Disconnected from server
解决方案
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