I have several servers that I'm spidering with FTPClient, I initially thought there was something wrong with what Im doing, however, dropping the version back to 2.0, and what I'm seeing goes away.
the following 'System Names' exhibit this lockup behaviour:
|UNIX Type\: L8||several sites Im talking to respond with this|
|System Name\: null||I found that on connect its telling me "Windows_NT"|
Ubuntu 6.06 and 9.04 systems work fine.
Attached will be a test-case maven project, just edit the 'blank.properties' in resources, with valid ftp server values. With commons-net-2.1 it locks up, but backing off to 2.0, it works.