Remember that passive mode reverses the setup direction of the FTP data channel.
Issuing the EPSV command is just like issuing the PASV command.
It's relatively boring, but invokes an interesting reply.
The EPSV command triggers a dynamic port allocation on the server,
opening a new TCP port to listen for a data connection
associated with a file transfer.
It operates like passive mode,
except the server's EPSV response has a slightly different format,
but serves an identical purpose as the PASV response.
The client is now aware that the server is listening on port 42579.
It issues the RETR command just like in IPv4,
specifying the file name of R1.cfg, which is the file to download.
This is sent in the FTP control channel.
The client needs to initiate a new data session using the dynamic port
learned via the EPSV reply from the previous slide,
which was 42579.
Once established,
the file is downloaded within the data channel
sourced from the EPSV dynamic port.
By now, you likely have these flows mastered.
To upload a file,
the client issues the STOR command with the file name to upload,
just like in IPv4.
Then the client initiates the FTP data session using port 42543,
which was allocated by the server and communicated by the EPSV response.
I omitted that step here for brevity.
Once established,
the client begins uploading the file's contents inside the data channel. Nothing new here.