FTP Clients not Displaying Files or Folders - KB Article #1102Related Articles --
When Serv-U is configured correctly but the network is not configured correctly it is common to find that users inside your network can see files and folders without problems, while users outside your network are unable to view files or folders. The most common error is a "timeout error", indicating that communications from the outside are not reaching Serv-U due to network configuration problems.
The most common cause of timeout errors and the inability to list files or folders is an improperly configured network. For FTP users to view files and folders, both port 21 and the server's PASV port range must be forwarded to the server. This runs contrary to the concept that port 21 is the only port used for FTP, because in fact FTP uses two ports - one for sending commands and another for sending data.
The directions at KB Article #1044 provides excellent steps on configuring your router and firewall to forward both port 21 and your user-defined PASV port range to allow users to view files and folders.
If the directory listing still does not complete or the FTP Clients in use cannot switch between connection types then have the clients download FTP Voyager. Then have them try to connect to Serv-U. If the connection still fails attach a copy of the log FTP Voyager creates to a support request and our technicians will help troubleshoot the problem.