java.net.SocketException：套接字失敗：EACCES（權限被拒絕）不能通過uses-permission解決

Question

我剛開始學習Android，並且嘗試從UDP客戶端成功發送字符串

我正在使用PacketSender作為服務器，但到目前為止我還沒有，因為我的許可被拒絕了。

這是代碼：

public class UDPStringSender extends AppCompatActivity {


Intent intent;
String ipAddress, port;
int portNumber;

boolean shouldLog;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_udp_string_sender);

    intent = getIntent();
    ipAddress = intent.getStringExtra("ip");
    port = intent.getStringExtra("port");
    portNumber = Integer.parseInt(port);

    Log.d("IP number is", ipAddress);
    Log.d("Port number is", port);

    shouldLog = true;
}


public void sendString(View view) {
    EditText stringField = (EditText)findViewById(R.id.sendableString);
    String sendableString = stringField.getText().toString();

    DatagramSocket _datagramSocket = null;
    try {
        _datagramSocket = new DatagramSocket();

        InetAddress serverIP = InetAddress.getByName(ipAddress);
        if(shouldLog)
            Log.d("InetAddress is", serverIP.toString());
        DatagramPacket _datagramPacket = new DatagramPacket(sendableString.getBytes(), sendableString.length(), serverIP, portNumber);
        if(shouldLog)
            Log.d("Packet to be send", _datagramPacket.toString());
        _datagramSocket.send(_datagramPacket);

    } catch (UnknownHostException e) {
        e.printStackTrace();
    } catch (SocketException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        if(_datagramSocket != null) {
            _datagramSocket.close();
            if(shouldLog)
                Log.d("is datagramSockedClosed", String.valueOf(_datagramSocket.isClosed()));
        }
    }
}

}

我的Android清單：

<?xml version="1.0" encoding="utf-8"?>

<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
    <activity android:name=".Interface">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
    <activity android:name=".UDPStringSender">
    </activity>
</application>

以及我的logcat：

11-23 15:58:50.652 31936-31936/co.barakastudio.layouttest W/System.err:  java.net.SocketException: socket failed: EACCES (Permission denied)
11-23 15:58:50.652 31936-31936/co.barakastudio.layouttest W/System.err:     at libcore.io.IoBridge.socket(IoBridge.java:619)
11-23 15:58:50.652 31936-31936/co.barakastudio.layouttest W/System.err:     at java.net.PlainDatagramSocketImpl.create(PlainDatagramSocketImpl.java:93)
11-23 15:58:50.652 31936-31936/co.barakastudio.layouttest W/System.err:     at java.net.DatagramSocket.createSocket(DatagramSocket.java:157)
11-23 15:58:50.652 31936-31936/co.barakastudio.layouttest W/System.err:     at java.net.DatagramSocket.<init>(DatagramSocket.java:80)
11-23 15:58:50.652 31936-31936/co.barakastudio.layouttest W/System.err:     at java.net.DatagramSocket.<init>(DatagramSocket.java:65)
11-23 15:58:50.652 31936-31936/co.barakastudio.layouttest W/System.err:     at co.barakastudio.layouttest.UDPStringSender.sendString(UDPStringSender.java:48)
11-23 15:58:50.652 31936-31936/co.barakastudio.layouttest W/System.err:     at java.lang.reflect.Method.invoke(Native Method)
11-23 15:58:50.652 31936-31936/co.barakastudio.layouttest W/System.err:     at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)
11-23 15:58:50.652 31936-31936/co.barakastudio.layouttest W/System.err:     at android.view.View.performClick(View.java:5697)
11-23 15:58:50.652 31936-31936/co.barakastudio.layouttest W/System.err:     at android.widget.TextView.performClick(TextView.java:10826)
11-23 15:58:50.652 31936-31936/co.barakastudio.layouttest W/System.err:     at android.view.View$PerformClick.run(View.java:22526)
11-23 15:58:50.652 31936-31936/co.barakastudio.layouttest W/System.err:     at android.os.Handler.handleCallback(Handler.java:739)
11-23 15:58:50.652 31936-31936/co.barakastudio.layouttest W/System.err:     at android.os.Handler.dispatchMessage(Handler.java:95)
11-23 15:58:50.652 31936-31936/co.barakastudio.layouttest W/System.err:     at android.os.Looper.loop(Looper.java:158)
11-23 15:58:50.652 31936-31936/co.barakastudio.layouttest W/System.err:     at android.app.ActivityThread.main(ActivityThread.java:7225)
11-23 15:58:50.652 31936-31936/co.barakastudio.layouttest W/System.err:     at java.lang.reflect.Method.invoke(Native Method)
11-23 15:58:50.652 31936-31936/co.barakastudio.layouttest W/System.err:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
11-23 15:58:50.652 31936-31936/co.barakastudio.layouttest W/System.err:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)
11-23 15:58:50.652 31936-31936/co.barakastudio.layouttest W/System.err: Caused by: android.system.ErrnoException: socket failed: EACCES (Permission denied)
11-23 15:58:50.652 31936-31936/co.barakastudio.layouttest W/System.err:     at libcore.io.Posix.socket(Native Method)
11-23 15:58:50.652 31936-31936/co.barakastudio.layouttest W/System.err:     at libcore.io.BlockGuardOs.socket(BlockGuardOs.java:282)
11-23 15:58:50.652 31936-31936/co.barakastudio.layouttest W/System.err:     at libcore.io.IoBridge.socket(IoBridge.java:604)
11-23 15:58:50.652 31936-31936/co.barakastudio.layouttest W/System.err:     ... 17 more

非常感謝您的寶貴時間，因為它可以節省大量的時間：)干杯，

Answer 1

自我報價：

<uses-permission>元素應位於<manifest>元素內部，但應位於<application>元素外部。 換句話說，這很好：

<?xml version="1.0" encoding="utf-8"?>
<manifest
  package="com.commonsware.android.something.something"
  xmlns:android="http://schemas.android.com/apk/res/android">

  <uses-permission android:name="INTERNET"/>
  <uses-permission android:name="ACCESS_NETWORK_STATE"/>

  <application
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme">

    <!-- cool stuff goes here -->

  </application>

</manifest>

但這不是：

<?xml version="1.0" encoding="utf-8"?>
<manifest
  package="com.commonsware.android.something.something"
  xmlns:android="http://schemas.android.com/apk/res/android">

  <application
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme">

    <uses-permission android:name="INTERNET"/>
    <uses-permission android:name="ACCESS_NETWORK_STATE"/>

    <!-- cool stuff goes here -->

  </application>

</manifest>

如果您手動分析清單（從主菜單中分析>檢查代碼...），Android Studio會報告此錯誤，但僅將元素放在錯誤的位置，它不會自動顯示警告。

Answer 2

據我所知，您不能在主線程中使用套接字... Android只是不允許這樣做。

我從沒嘗試過DatagramSocket，只是嘗試了普通的Socket，但我認為這沒有什么不同。

您應該創建一個新線程並將字符串發送到那里。

快速示例（不是最佳實踐，但很簡短；）：

Thread thread = new Thread(new Runnable() {
     public void run() {
          // send the String here
     }
});  
thread.start();

這將在后台發送String，並且一旦方法run()終止，線程將被銷毀。