Possible bug: FileZilla should open a data connection when storing empty files

[benallfree]

I'm hitting a timeout error with https://github.com/QuorumDMS/ftp-srv where it is waiting for a data connection before responding to STOR with a 150.

FileZilla apparently doesn't open a data connection for 0-byte files, or perhaps it waits until after the 150 response. In any case, FileZilla behaves differently for 0 byte files.

Cross-posted to https://github.com/QuorumDMS/ftp-srv/issues/366

[botg]

The server must not assume a particular ordering. Following the PASV/PORT/EPRT/EPSV commands, it must independently handle the data connection establishment and the control connection commands. The network packets of the two different connections can be interleaved in any order.