如何使用像InetAddress这样的套接字

Question

我是韩国的android开发者。目前，我已经制作了一个关于socket的项目。 但是，我有一些问题，所以我进入了这个网站。 看！

 class PingCheckThread implements Runnable{

            @Override
            public void run() {
                // TODO Auto-generated method stub
                while(!Thread.currentThread().isInterrupted()){
                    try {
                        if(device != null){
                            for(int i = 0; i < device.size(); i++){
                                String info = (String) device.get(i);
                                int first = info.indexOf(":");
                                int last = info.lastIndexOf(":");
                                String ip = info.substring(first, last);
                                InetAddress targetIp = 
Inet4Address.getByAddress(ip.getBytes()); ///< error!!

                                if(targetIp.isReachable(60000)){
                                    Log.v(TAG, "Connection Ok");
                                }else{
                                    Log.v(TAG, "Connection Fail");
                                }

                            }
                        }
                        Thread.sleep(60000);
                    } catch (Exception e) {
                        // TODO Auto-generated catch block
                        Log.v(TAG, e.getMessage());
                    }
                }
            }
        }

日志与GT;

08-26 11:27:34.124: W/dalvikvm(3612): threadid=13: thread exiting with uncaught exception (group=0x2c43b930)
08-26 11:27:35.464: E/AndroidRuntime(3612): FATAL EXCEPTION: Thread-216
08-26 11:27:35.464: E/AndroidRuntime(3612): java.lang.NullPointerException
08-26 11:27:35.464: E/AndroidRuntime(3612):  at com.skb.sportscompanion.tv.SportsCompanionTV$PingCheckThread.run(SportsCompanionTV.java:206)
08-26 11:27:35.464: E/AndroidRuntime(3612):  at java.lang.Thread.run(Thread.java:856)

为什么inetAddress具有nullpointerexception？它似乎是InetAddress.getByName，InetAddress.geyByAddress。我想知道这个错误。 我已经写过uses-permission。 机器人：名字= “android.permission.INTERNET对” 机器人：名称= “android.permission.ACCESS_NETWORK_STATE”