How to validate the URL for a file

question

#1

Suppose I have a file with the following url I need to download it in Julia
ftp://hello.com/world.zip.

How to validate the URL before downloading it?

Motivations of my question:

  1. The silly servers in my workspace sometime cannot access remote ftp files, probably because of firewall. Just want to be informed when files are unavailable.
  2. I guess it is system specific because of different download commands. Is there any robust method for it?