android - No files detected on FTP server -

i'm running ftp server, contains file in root directory: "/". program able connect , login server , able change root directory. when try list name of files , print out single file located, gives me error saying: "attempt read null array". here code:

    ftpclient = new ftpclient();     log.d("loginactivity", "ftp");     ftpclient.connect("xxx.xxx.x.xx", xx);     boolean connected = ftpclient.isconnected();     if(connected){         log.d("loginactivity", "connected: true");     }     boolean loggedin = ftpclient.login("name", "password");     if(loggedin){     log.d("loginactivity", "loggedin: true");     }     boolean founddirectory = ftpclient.changeworkingdirectory("/");     if(founddirectory){         log.d("loginactivity", "directory found: true");     }     string[] files = ftpclient.listnames("/");     log.d("loginactivity", files[0]); 

how come no files found, when know there 1 located in rootdirectory?