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JSI Tip 2936. FTP client receives error 425?

When you connect to an FTP server using the Windows NT or Windows 2000 command-line FTP client and issue a quote <command>, the next command that you issue may generate a 425 Can't open data connection error.

When an active mode FTP client passes a command to a FTP server, the client passes a port on which it listens for a server response. If the client sends a command that does not require a data port, it doesn't send one.

FTP clients can pass the server commands that they do not interpret. These commands use the quote <command> syntax. The client sends these commands without a listen port for the data, so the server generates the 425 error if a port is required.

The ls command requires a listen port, and therefore sends one. The Quote command doesn't send a port, so Quote ls generates a 425 error.

The Windows FTP client does not support passive mode, so it always needs to send a port when issuing a command that returns data.

The following are the valid commands:

 ftp> help
Commands may be abbreviated.  Commands are:

!               delete          literal         prompt          send
?               debug           ls              put             status
append          dir             mdelete         pwd             trace
ascii           disconnect      mdir            quit            type
bell            get             mget            quote           user
binary          glob            mkdir           recv            verbose
bye             hash            mls             remotehelp
cd              help            mput            rename
close           lcd             open            rmdir

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