環境：
ftp服務器上存在/A/B目錄，目錄下有個文件夾ABC，向獲取ftp服務器上文件夾ABC下的文件列表

代碼：在irb上測試

require 'net/ftp'
ftp = Net::FTP.open("200.200.0.3","test","test")
ftp.voidcmd("CWD /A/B")
ftp.nlst("ABC")-------这里报错：

報錯內容

irb(main):234:0* ftp.nlst("ABC")
SocketError: getnameinfo: ����������������������
        from D:/Sangfor-ATT/Ruby200/lib/ruby/2.0.0/net/ftp.rb:1083:in `addr'
        from D:/Sangfor-ATT/Ruby200/lib/ruby/2.0.0/net/ftp.rb:1083:in `block (2levels) in <class:BufferedSocket>'
        from D:/Sangfor-ATT/Ruby200/lib/ruby/2.0.0/net/ftp.rb:383:in `makeport'
        from D:/Sangfor-ATT/Ruby200/lib/ruby/2.0.0/net/ftp.rb:421:in `transfercmd'
        from D:/Sangfor-ATT/Ruby200/lib/ruby/2.0.0/net/ftp.rb:514:in `block (2 levels) in retrlines'
        from D:/Sangfor-ATT/Ruby200/lib/ruby/2.0.0/net/ftp.rb:199:in `with_binary'
        from D:/Sangfor-ATT/Ruby200/lib/ruby/2.0.0/net/ftp.rb:512:in `block in retrlines'
        from D:/Sangfor-ATT/Ruby200/lib/ruby/2.0.0/monitor.rb:211:in `mon_synchronize'
        from D:/Sangfor-ATT/Ruby200/lib/ruby/2.0.0/net/ftp.rb:511:in `retrlines'
        from D:/Sangfor-ATT/Ruby200/lib/ruby/2.0.0/net/ftp.rb:744:in `nlst'
        from (irb):234
        from D:/Sangfor-ATT/Ruby200/bin/irb:12:in `<main>'

不知道哪裏出了錯誤，向各位大牛求教