While investigating options for deploying Sitecore to Azure, I found a TeamCity deploy plugin that supported FTP (among other things). Unfortunately, after trying to get it up and running I ran into the following 501 error while using FTPES (explicit FTPS):
“Failed to upload artifacts via FTP. Reply was: 501 server cannot accept argument”
Investigating on the server, I found the following in the IIS server logs:
“Client IP on the control channel didn’t match the client IP on the data channel”
A little bit of Google digging later, I found some chatter on the issue on the plugin’s GitHub issues list. That thread pointed to a patch build with options to specify Active versus Passive in the FTP mode. It turns out I needed Passive, but the original plugin download didn’t support it.
If you also need this functionality, this is the link to the plugin developer’s build which supports an option to specify Passive versus Active on the FTP mode:
St-Cyr Thoughts 