proxy - Controlling a connection to two remote systems

The proxy command controls a connection to two remote systems for transferring files between these two remote systems. A requirement here is that the second remote system supports the PASV or EPSV command.

proxy

<ftp-command>

<ftp-command>

Specifies an FTP client command:

• In order to establish the control connection to the second system, the first <ftp-command> must be the open command.

• When you enter proxy help the other FTP commands are shown which can be executed on the secondary connection.

The following commands behave differently if they are prefixed with proxy:

• get and mget transfer files from the first server to the second server.

• put, mput and append transfer files from the second server to the first server.

The figure below sketches the basic procedure for transferring a file <file> between two remote servers A and B. C is the client.

Server A	Server B
C      A: connect (open)	C     B: connect (proxy open)
Processing the specified proxy get <file>:
	C     B: PASV B    C:  227 Entering Passive Mode (a1, a2, a3, a4, p1, p2)
C     A:  PORT a1, a2, a3, a4, p1, p2 A    C: 200 PORT command successful C     A:  RETR <file>
	C     B: STOR <file>
A    B: Connect to Server B (a1,a2,a3,a4), Port(p1,p2)

Figure 3: Transferring a file <file> between two remote servers

Example

All files of the ID userid1 on the remote system1 are to be transferred to the ID userid2 on the remote system2.

ftp> open system1        Open control connection to 1st server
userid1                  .
.                        .
.                        .
.                        .
ftp> proxy open system2 Open control connection to 2nd server
userid2                  .
.                        .
.                        .
.                        .
ftp> proxy?              Which proxy commands are supported?
ftp> proxy mget *        Transfer filessystem1 -> system2
ftp> proxy ls            Check result
ftp> proxy close         Close secondary control connection

The status command returns the following output in this case:

ftp> status
Connected to PGAB0021, port21.
Connected for proxy commands to system2.
Passive Mode: off
...