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From Ted Gittinger <tgitt...@gmail.com>
Subject [NET] FTPClientExample Hangs on Disconnect
Date Fri, 29 Jul 2011 20:58:22 GMT
I’ve been trying to use FTPClientExample.java to FTPS(FTP over SSL) to an
IBM mainframe.  (From the 3.0.1 source.) It seems to work except the
‘ftp.disconnect()’
hangs and the thread never terminates.  Here is the console output:



220-FTPSERV2 IBM FTP CS V1R11 at serverNameHere, 16:48:22 on 2011-07-27.

220-Welcome to the xyz FTP Server

220 Connection will close if idle for more than 5 minutes.

AUTH TLS

234 Security environment established - ready for negotiation

PBSZ 0

200 Protection buffer size accepted

PROT P

200 Data connection protection set to private

Connected serverAddressHere on serverPortHere

USER *******

331 Send password please.

PASS *******

230-******************************************************************

230-*  Welcome JohnDoh to the XYZ system.

230-*  It is Wed Jul 27 16:48:24 2011.

230-*  Unauthorized use is prohibited. Usage may be subject to

230-*  security testing and monitoring. Misuse is subject to criminal

230-*  prosecution. There is no expectation of privacy except as

230-*  provided by law.

230-******************************************************************

230 JOHNDOH is logged on.  Working directory is "JOHNDOH.".

SYST

215 MVS is the operating system of this server. FTP Server is running on
z/OS.

PASV

227 Entering Passive Mode (xxx,xxx,xxx,xxx,x,xxx)

STOR 'SOMEFILE.NEW.EXAMPLE.TXT'

125 Storing data set SOMEFILE.NEW.EXAMPLE.TXT

250 Transfer completed successfully.

NOOP

200 OK

QUIT

221 Quit command received. Goodbye.



Note that the last reply from the server indicates a successful QUIT
command. However, the program never terminates.


Here's the debug information from the SSL socket which shows the QUIT and
then the attempted 'close_notify'.  (For those that follow, I added
-Djavax.net.debug=all to the virtual machine arguments to get the debug
info.)


MAC:  update
Padded plaintext before ENCRYPTION:  len = 26
0000: 51 55 49 54 0d 0a 08 01  8d 8a c7 0a 02 d8 95 e9  QUIT............
0010: 6f ff c5 c2 ce ae 93 91  dd 5e                    o.........

main, WRITE: SSLv3 Application Data, length = 26
[Raw write]: length = 31
0000: 17 03 00 00 1a b3 6e 70  da b4 d0 b9 a2 49 58 2d  ......np.....IX.
0010: 5a dd b5 3f 9d ea d1 66  ce 46 53 33 f8 a2 2a     Z......f.FS3...

QUIT
[Raw read]: length = 5
0000: 17 03 00 00 39                                     ....9

[Raw read]: length = 57
0000: 43 aa e1 a9 9e 49 38 38  38 b0 fd 14 4c e0 eb d1  C....I888...L...
0010: 9c 5e 5b 83 9f c5 c8 30  ba 9e 91 54 14 ab da a8  .......0...T....
0020: f3 81 3d a2 46 22 a0 5c  a7 30 30 32 66 3a 2a ee  ....F....002f...
0030: 15 03 e2 30 35 89 78 ec  30                       ...05.x.0

main, READ: SSLv3 Application Data, length = 57
Padded plaintext after DECRYPTION:  len = 57
0000: 32 32 31 20 51 75 69 74  20 63 6f 6d 6d 61 6e 64  221.Quit.command
0010: 20 72 65 63 65 69 76 65  64 2e 20 47 6f 6f 64 62  .received..Goodb
0020: 79 65 2e 0d 0a 86 f4 3c  7d ca b9 de f4 e6 e3 20  ye..............
0030: 35 cf 2e 2a b3 c4 70 ae  71                       5.....p.q

MAC:  update
221 Quit command received. Goodbye.
3.0.1, b4 closing socket 6f0f6f0f[SSL_RSA_WITH_RC4_128_SHA:
Socket[addr=hostnamehere/ipaddresshere port=xxxx,localport=xxxx]]
main, called close()
main, called closeInternal(true)
main, SEND SSLv3 ALERT:  warning, description = close_notify
MAC:  update
Padded plaintext before ENCRYPTION:  len = 22
0000: 01 00 1d 3a 7f 09 44 9c  b7 9f 5c 2b 6c 71 d6 a1  ......D.....lq..
0010: 86 fc a3 f8 6a 51                                  ....jQ

main, WRITE: SSLv3 Alert, length = 22
[Raw write]: length = 27
0000: 15 03 00 00 16 e6 ad b4  00 9a c4 fc cd 30 b4 4d  .............0.M
0010: a9 7a 82 2b a8 8a 4c 70  c4 f7 41                 .z....Lp..A

main, waiting for close_notify or alert: state 5  <<<<<<<<<<<
THE SSL SOCKET
IS WAITING FOR A REPLY FROM THE SERVER...



Notice that the SSL socket in my program is waiting for a 'close_notify'
response from the FTP server.  It waits forever.  I think this is because
the QUIT command closes the connection on the server.


So I commented out the 'logout(QUIT)' and ran the program again:


NO LOGOUT/QUIT HERE, IT'S COMMENTED OUT


3.0.1, b4 closing socket 71037103[SSL_RSA_WITH_RC4_128_SHA:
Socket[addr=addressGoesHere,port=portHere,localport=portHere]]
main, called close()
main, called closeInternal(true)
main, SEND SSLv3 ALERT:  warning, description = close_notify
MAC:  update
Padded plaintext before ENCRYPTION:  len = 22
0000: 01 00 5b 7e 2e ac b5 87  21 0a 2b a6 6d cd 6b f1  ............m.k.
0010: b4 61 ad 5c 51 85                                  .a..Q.

main, WRITE: SSLv3 Alert, length = 22
[Raw write]: length = 27
0000: 15 03 00 00 16 76 e3 2b  a6 dd a9 b2 30 b2 c6 ea  .....v......0...
0010: a9 cb e8 75 6c 22 ed 46  e4 0e 13                 ...ul..F...

main, waiting for close_notify or alert: state 5  <<<<<<<<<<<<<<
HERE'S
WHERE THE HANG OCCURRED IN THE PREVIOUS RUN
[Raw read]: length = 5
0000: 15 03 00 00 16                                     .....

[Raw read]: length = 22
0000: e1 22 37 3a 99 bd 2f 2f  53 b1 a5 be a3 c5 7e bc  ..7.....S.......
0010: 73 69 4b a9 a4 4b                                  siK..K

main, READ: SSLv3 Alert, length = 22
Padded plaintext after DECRYPTION:  len = 22
0000: 01 00 18 ca 28 9c fc c1  83 ba 20 3b a6 f8 30 36  ..............06
0010: fa 45 7e bc 4e d6                                  .E..N.

MAC:  update
main, RECV SSLv3 ALERT:  warning, close_notify  <<<<<<<<<<<<<<<<<<
HERE'S
WHERE THE FTP SERVER SENT A close_notify RESPONSE
main, called closeInternal(false)
main, close invoked again; state = 5
3.0.1, after closing socket
3.0.1, b4 closing closeable java.net.SocketInputStream@60636063
3.0.1, after closing closeable
3.0.1, b4 closing closeable java.net.SocketOutputStream@608f608f
3.0.1, after closing closeable
******** 3.0.1 exiting, error = 'false'

As you can see, commenting out the 'logout/QUIT' statement allowed the
program to terminate normally.


So should I simply disconnect from the server or should I QUIT and then
disconnect?


http://www.faqs.org/rfcs/rfc959.html

LOGOUT (QUIT)



            This command terminates a USER and if file transfer is not

            in progress, the server closes the control connection.  If

            file transfer is in progress, the connection will remain

            open for result response and the server will then close it.

            If the user-process is transferring files for several USERs

            but does not wish to close and then reopen connections for

            each, then the REIN command should be used instead of QUIT.


>>> Does this mean that QUIT closes the connection on the server? (It looks
like it should.)



            An unexpected close on the control connection will cause the

            server to take the effective action of an abort (ABOR) and a

            logout (QUIT).

>>> Does this mean that disconnecting without QUIT will force the FTP
session to logout automatically?


Thanks for the help!

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