Android example source code file (DaemonProxy.java)

This example Android source code file (DaemonProxy.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

android, daemonproxy, dbg, end_of_arguments, internet, interruptedexception, io, ioexception, localsocket, localsocketaddress, net, network, os, outputstream, runtimeexception, serializable, string, svc_state_cmd_prefix, vpn, waiting_time

The DaemonProxy.java Android example source code

/*
 * Copyright (C) 2009, The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.server.vpn;

import android.net.LocalSocket;
import android.net.LocalSocketAddress;
import android.net.vpn.VpnManager;
import android.os.SystemProperties;
import android.util.Log;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.Serializable;

/**
 * Proxy to start, stop and interact with a VPN daemon.
 * The daemon is expected to accept connection through Unix domain socket.
 * When the proxy successfully starts the daemon, it will establish a socket
 * connection with the daemon, to both send commands to the daemon and receive
 * response and connecting error code from the daemon.
 */
class DaemonProxy implements Serializable {
    private static final long serialVersionUID = 1L;
    private static final boolean DBG = true;

    private static final int WAITING_TIME = 15; // sec

    private static final String SVC_STATE_CMD_PREFIX = "init.svc.";
    private static final String SVC_START_CMD = "ctl.start";
    private static final String SVC_STOP_CMD = "ctl.stop";
    private static final String SVC_STATE_RUNNING = "running";
    private static final String SVC_STATE_STOPPED = "stopped";

    private static final int END_OF_ARGUMENTS = 255;

    private String mName;
    private String mTag;
    private transient LocalSocket mControlSocket;

    /**
     * Creates a proxy of the specified daemon.
     * @param daemonName name of the daemon
     */
    DaemonProxy(String daemonName) {
        mName = daemonName;
        mTag = "SProxy_" + daemonName;
    }

    String getName() {
        return mName;
    }

    void start() throws IOException {
        String svc = mName;

        Log.i(mTag, "Start VPN daemon: " + svc);
        SystemProperties.set(SVC_START_CMD, svc);

        if (!blockUntil(SVC_STATE_RUNNING, WAITING_TIME)) {
            throw new IOException("cannot start service: " + svc);
        } else {
            mControlSocket = createServiceSocket();
        }
    }

    void sendCommand(String ...args) throws IOException {
        OutputStream out = getControlSocketOutput();
        for (String arg : args) outputString(out, arg);
        out.write(END_OF_ARGUMENTS);
        out.flush();

        int result = getResultFromSocket(true);
        if (result != args.length) {
            throw new IOException("socket error, result from service: "
                    + result);
        }
    }

    // returns 0 if nothing is in the receive buffer
    int getResultFromSocket() throws IOException {
        return getResultFromSocket(false);
    }

    void closeControlSocket() {
        if (mControlSocket == null) return;
        try {
            mControlSocket.close();
        } catch (IOException e) {
            Log.w(mTag, "close control socket", e);
        } finally {
            mControlSocket = null;
        }
    }

    void stop() {
        String svc = mName;
        Log.i(mTag, "Stop VPN daemon: " + svc);
        SystemProperties.set(SVC_STOP_CMD, svc);
        boolean success = blockUntil(SVC_STATE_STOPPED, 5);
        if (DBG) Log.d(mTag, "stopping " + svc + ", success? " + success);
    }

    boolean isStopped() {
        String cmd = SVC_STATE_CMD_PREFIX + mName;
        return SVC_STATE_STOPPED.equals(SystemProperties.get(cmd));
    }

    private int getResultFromSocket(boolean blocking) throws IOException {
        LocalSocket s = mControlSocket;
        if (s == null) return 0;
        InputStream in = s.getInputStream();
        if (!blocking && in.available() == 0) return 0;

        int data = in.read();
        Log.i(mTag, "got data from control socket: " + data);

        return data;
    }

    private LocalSocket createServiceSocket() throws IOException {
        LocalSocket s = new LocalSocket();
        LocalSocketAddress a = new LocalSocketAddress(mName,
                LocalSocketAddress.Namespace.RESERVED);

        // try a few times in case the service has not listen()ed
        IOException excp = null;
        for (int i = 0; i < 10; i++) {
            try {
                s.connect(a);
                return s;
            } catch (IOException e) {
                if (DBG) Log.d(mTag, "service not yet listen()ing; try again");
                excp = e;
                sleep(500);
            }
        }
        throw excp;
    }

    private OutputStream getControlSocketOutput() throws IOException {
        if (mControlSocket != null) {
            return mControlSocket.getOutputStream();
        } else {
            throw new IOException("no control socket available");
        }
    }

    /**
     * Waits for the process to be in the expected state. The method returns
     * false if after the specified duration (in seconds), the process is still
     * not in the expected state.
     */
    private boolean blockUntil(String expectedState, int waitTime) {
        String cmd = SVC_STATE_CMD_PREFIX + mName;
        int sleepTime = 200; // ms
        int n = waitTime * 1000 / sleepTime;
        for (int i = 0; i < n; i++) {
            if (expectedState.equals(SystemProperties.get(cmd))) {
                if (DBG) {
                    Log.d(mTag, mName + " is " + expectedState + " after "
                            + (i * sleepTime) + " msec");
                }
                break;
            }
            sleep(sleepTime);
        }
        return expectedState.equals(SystemProperties.get(cmd));
    }

    private void outputString(OutputStream out, String s) throws IOException {
        byte[] bytes = s.getBytes();
        out.write(bytes.length);
        out.write(bytes);
        out.flush();
    }

    private void sleep(int msec) {
        try {
            Thread.currentThread().sleep(msec);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        }
    }
}