Are you using ISA or some other firewall/proxy? That's generally what causes a 501
Best bet is to wireshark the process and attach the cap - very hard to figure it out otherwise. From: ozdotnet-boun...@ozdotnet.com [mailto:ozdotnet-boun...@ozdotnet.com] On Behalf Of Greg Keogh Sent: Thursday, 17 October 2013 9:28 AM To: ozDotNet Subject: [OT] FTP client problems Folks, I'm getting conflicting behaviour in FTP clients on our new server. We installed an app in this new server and it died attempting to GET a file from a remote FTP server. So I ran ftp.exe<ftp://ftp.exe> from the command prompt to do the same thing as the app does in code to see what happens (thinking that ftp.exe<ftp://ftp.exe> is a nice vanilla test). It takes my user and password okay, but an 'ls' command says "501 Server cannot accept argument". I tried PASV mode and it does the same thing. Next test from Windows Explorer asks for my credentials and then lists the FTP server's file okay. So that's weird ... the app and ftp.exe<ftp://ftp.exe> fail, but Windows Explorer works. Can anyone suggest why? Different authentication modes? This is a serious problem that has stopped the rollout of the app. Greg K P.S. I know that FTP is ancient, but it's being used for historical reasons. I've told the app's author to use HTTP instead and have supplied some sample code.