People have been using this ftp server for years and it doesn't crash.

Files can be directly stored on a ftp server.

After all, they didn't write the ftp server.

The repro case no longer crashes the ftp server.

FTP servers became the primary method in later years.

A direct transfer from one FTP server to another is also possible.

So normally you have to log into an FTP server.

It in a sense could even act as a proxy for other FTP servers.

Direct access from the outside can't be initiated with the internal FTP server.

Thus, the FTP server met the second requirement of being accessible to experts in the field.