Apache Commons FTP被动模式，如何设置远程监听端口(数据流)

Question

我尝试使用apache-commons-net-3.7.2(隐式TLS，使用客户端证书+登录名/密码的双因素身份验证(连接FTP服务器。

我可以对自己进行身份验证，以被动模式进入，但客户端无法成功连接到服务器以通过数据套接字获取数据。

我可以在同一台计算机上连接WinSCP(相同的设置(。我已经激活了WinSCP日志以查看协议详细信息，并使用相同的选项调整了我的源代码。我可以用ProtocolCommandListener验证我的协议是否正常。我知道需要被动模式，因为WinSCP发出PASV命令。

我可以看到WinSCP连接到端口62564上的数据套接字(我已经用XXX替换了FTP IP地址(

2021-01-06 10:25:35.575 227 Entering Passive Mode (192,168,4,122,244,100).
2021-01-06 10:25:35.575 Server sent passive reply with unroutable address 192.168.4.122, using host address instead.
2021-01-06 10:25:35.575 MLSD
2021-01-06 10:25:35.575 Connexion à 83.XXX.XXX.XXX:62564...
2021-01-06 10:25:35.604 150 Transferring directory

此外，我可以看到服务器为PASV命令发送的回复不包括要连接的端口。

public class TestApi {

public static void _parseExtendedPassiveModeReply(String reply)
{
reply = reply.substring(reply.indexOf('(') + 1,
reply.indexOf(')')).trim();

char delim1, delim2, delim3, delim4;
delim1 = reply.charAt(0);
delim2 = reply.charAt(1);
delim3 = reply.charAt(2);
delim4 = reply.charAt(reply.length()-1);

if (!(delim1 == delim2) || !(delim2 == delim3)
|| !(delim3 == delim4)) {
System.out.println("Could not parse extended passive host information.nServer Reply: " + reply);
}

int port;
try
{
port = Integer.parseInt(reply.substring(3, reply.length()-1));
}
catch (NumberFormatException e)
{
System.out.println("Could not parse extended passive host information.nServer Reply: " + reply);
}
}   

public static void main(String[] args) throws SocketException, IOException, GeneralSecurityException {
String hostname = args[0];
int port = Integer.parseInt(args[1]);
String login = args[2];
String pwd = args[3];
FTPSClient client = new FTPSClient("TLS",true);

File clientCertStore = new File("myJCEKS keystore");        
KeyManager keyManager = KeyManagerUtils.createClientKeyManager("JCEKS",clientCertStore,"","myalias","");        
client.setKeyManager(keyManager);

client.connect(hostname, port);
int reply = client.getReplyCode();
if (!FTPReply.isPositiveCompletion(reply)) {
client.disconnect();
System.err.println("FTP server refused connection.");
System.exit(1);
} else {
if (client.login(login, pwd)) {

client.addProtocolCommandListener(new PrintCommandListener(new PrintWriter(System.err), true));
client.sendCommand("OPTS","UTF8 ON");
client.sendCommand("PBSZ","0");
client.sendCommand("PROT","P");

int retour = client.pasv();
System.out.println(retour);
_parseExtendedPassiveModeReply(client.getReplyString());                

System.out.println(client.printWorkingDirectory());
reply = client.getReplyCode();
System.out.println(reply);

System.out.println(client.listHelp());

//it freezes here, after sending MLDS command 
//same thing using regular api for listing files (WinSCP use MLSD while regular api uses LIST)      
client.sendCommand("MLSD");
//and so on
System.out.println("LOGOUT");
client.logout();
} else {
System.out.println("echec login");
}
}
}
}

我想API不知道必须在哪个端口上发送数据请求，并使用默认值，这是不好的。我不知道WinSCP是如何成功计算62564端口号的。

OPTS UTF8 ON
200 Command OPTS succeed
PBSZ 0
200 PBSZ=0
PROT P
200 PRIVATE data channel protection level set
PASV
227 Entering Passive Mode (192,168,4,122,245,74).
227
PWD
Could not parse extended passive host information.
Server Reply: 192,168,4,122,245,74
Could not parse extended passive host information.
Server Reply: 192,168,4,122,245,74
257 "/" is current directory
/
257
HELP
214-The following commands are implemented
ABOR  ACCT  ALLO* APPE  CDUP  CWD   DELE  FEAT+ HELP
HOST+ LANG+ LIST  MDTM+ MLST+ MKD   MODE  NLST  NOOP
OPTS+ PASS  PASV  PORT  PWD   QUIT  REIN  REST  RETR
RMD   RNFR  RNTO  SITE  SIZE  SMNT  STAT  STOR  STOU
STRU* SYST  TYPE  USER  XCUP  XCRC  XCWD  XMD5  XMKD
XPWD  XRMD  XSIGN XSHA1 XSHA256 XSHA512 XQUOTA
214 Help complete
214-The following commands are implemented
ABOR  ACCT  ALLO* APPE  CDUP  CWD   DELE  FEAT+ HELP
HOST+ LANG+ LIST  MDTM+ MLST+ MKD   MODE  NLST  NOOP
OPTS+ PASS  PASV  PORT  PWD   QUIT  REIN  REST  RETR
RMD   RNFR  RNTO  SITE  SIZE  SMNT  STAT  STOR  STOU
STRU* SYST  TYPE  USER  XCUP  XCRC  XCWD  XMD5  XMKD
XPWD  XRMD  XSIGN XSHA1 XSHA256 XSHA512 XQUOTA
214 Help complete
MLSD

在API文档、源代码、FTP RFC中搜索了几个小时后，我不知道该怎么做了

Answer 1

您的假设是错误的。您没有设置端口。服务器告诉您要连接的端口。

对于WinSCP:

2021-01-06 10:25:35.575 227进入被动模式(192168,4122，244，100(

2021-01-06 10:25:35.575 Connexionà83.XXX.XXX.XXX:62564…

其中62564=(244<<8(+100

参见RFC 959第4.1.2节。传输参数命令，第28页。

---

PASV响应的解析失败，因为您使用了错误的代码。_parseExtendedPassiveModeReply用于EPSV。对于PASV，请使用_parsePassiveModeReply。在那里你还会看到上面公式的实现：

int oct1 = Integer.parseInt(m.group(2));
int oct2 = Integer.parseInt(m.group(3));
__passivePort = (oct1 << 8) | oct2;