Emacs AngeFTP fails on macOS 10.14 with GNU inetutils FTP

[Alex Bochannek]

Hello!

I sent in bug 48494: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=48494
to Emacs, but I am starting to think this might be an inetutils issue.

I observed that AngeFTP cannot parse the output of the GNU inetutils FTP
client on macOS 10.14. It errors out with "FTP Error: OPEN request
failed:" and the process buffer shows the following:

ftp> open ftp.tcl.tk
open ftp.tcl.tk
cd /
cd /
cd /
cd /
cd /
cd /
cd /
cd /
cd /
cd /
cd /
cd /
Connected to ftp.tcl.tk.
421 Service not available, remote server has closed connection
ftp> Not connected.
ftp> Not connected.
ftp> Not connected.
ftp> Not connected.
ftp> Not connected.
ftp> Not connected.
ftp> 

This appears to be caused by readline being enabled for ftp and is
resolved when disabling it. The tnftp documentation suggests that this
might be necessary for AngeFTP.

Netkit-ftp on Linux does not exhibit this problem even with readline
enabled; I could not test GNU inetutils on Linux. I tested tnftp on
macOS and it also did not exhibit this problem even with readline
enabled.

Tested versions:
ftp (GNU inetutils) 2.0 macOS 10.14.6
tnftp-20200705 macOS 10.14.6
netkit-ftp 0.17-34.1 Ubuntu 20.04.2 LTS

Is this a known problem? Does this maybe work as intended?

Thanks!

-- 
Alex.