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FTP client cannot send data to GuildFTPd FTP server

Technote (troubleshooting)


Problem(Abstract)

A put or get is done from the FTP client. A PORT command is sent to the server, and it appears the client is not waiting for the reply
200 PORT command successful
from the server before it sends the STOR command. This causes the session to fail.

Cause

The FTP client sends a SITE command to the server before it sends the PORT command. The GuildFTPd FTP server responds with a 214 'SITE' command not understood reply which ends with two sets of carriage-return line-feed hex characters: x'0D0A 0D0A'. Per RFC 959, there should only be one x'0D0A'.

When the client reads the 214 reply, it reads the first x'0D0A', and the second x'0D0A' stays in the buffer. When the client sends the PORT command to the server and checks for a response, it reads this remaining x'0D0A'. The client interprets this as a failure, and brings down its listen on the port for the data connection.

Any SYNs sent from the server during this time will be reset. The client then tries to recover from this and puts up a listen using the control connection port and sends the STOR command to the server. The remote server is not able to open the data connection, so it may reply 425 Can't build data connection.

The following is a sample joblog for this failure:


    EZA1736I PUT file
    EZA1701I >>> SITE VARrecfm LRECL=4092 RECFM=VB BLKSIZE=4096
    214 'SITE' command not understood.
    EZA1701I >>> PORT 123,456,123,123,120,144
    EZA1701I >>> STOR file
    200 PORT command successful.
    EZA1735I FTP Return Code = 27200, Error Code = 00002
    EZA1701I >>> QUIT
    150 Opening ascii mode data connection for file

You can confirm from the initial 220 connection reply that this is a GuildFTPd FTP server.

Resolving the problem

Issue the SENDSite subcommand in the session before issuing the put or get subcommand. This will tell the client not to send the SITE command to the server. By default, the SENDSite subcommand is turned on when you start an FTP session. Each time you use the SENDSite subcommand, it is toggled on and off.

For more information on the SENDSite subcommand, please review section 5.64 SENDSite subcommand--Toggle the sending of site information in the z/OS Communications Server: IP User's Guide and Commands.

Document information

More support for: z/OS Communications Server
All

Software version: 1.6, 1.7, 1.8, 1.9, 1.10, 1.11, 1.12, 1.13, 2.1, 2.2, 2.3

Operating system(s): z/OS

Reference #: 1213496

Modified date: 02 August 2005


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