java學習小筆記（三.socket通信）

三，socket通信
1.http://blog.csdn.net/kongxx/article/details/7288896這個人寫的關於socket通信不錯，循序漸進式的講解，用代碼示例說明，運用流和socket進行遠程通訊

2.最簡單的socket是一個服務端對應一個客戶端
 server的寫法

ServerSocket server = new ServerSocket(10000);
        Socket socket = server.accept();
        BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
        PrintWriter out = new PrintWriter(socket.getOutputStream());

        while (true) {
            String msg = in.readLine();
            System.out.println(msg);
            out.println("Server received " + msg);
            out.flush();
            if (msg.equals("bye")) {
                break;
            }
        }
        socket.close();

 
client的寫法

Socket socket = new Socket("localhost", 10000);
        BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
        PrintWriter out = new PrintWriter(socket.getOutputStream());
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));

        while (true) {
            String msg = reader.readLine();
            out.println(msg);
            out.flush();
            if (msg.equals("bye")) {
                break;
            }
            System.out.println(in.readLine());
        }
        socket.close();

3.複雜一點的就是多個客戶端同時訪問服務器。在客戶端使用循環啓動多個客戶端訪問同一服務端，在服務端只要server.accept()一接收到就新建線程，然後把把上面的讀寫操作放進線程內處理。

4.如果要利用socke傳遞對象，就要讓對象實現Serializable 序列化接口，使用ObjectInputStream和ObjectOutputStream進行序列化和反序列化
server的寫法

 ObjectInputStream is = null;
                ObjectOutputStream os = null;
                try {
                    is = new ObjectInputStream(new BufferedInputStream(socket.getInputStream()));
                    os = new ObjectOutputStream(socket.getOutputStream());

                    Object obj = is.readObject();
                    User user = (User)obj;
                    System.out.println("user: " + user.getName() + "/" + user.getPassword());

                    user.setName(user.getName() + "_new");
                    user.setPassword(user.getPassword() + "_new");

                    os.writeObject(user);
                    os.flush();
                } catch (IOException ex) {

client的寫法

ObjectOutputStream os = null;
            ObjectInputStream is = null;

            try {
                socket = new Socket("localhost", 10000);

                os = new ObjectOutputStream(socket.getOutputStream());
                User user = new User("user_" + i, "password_" + i);
                os.writeObject(user);
                os.flush();

                is = new ObjectInputStream(new BufferedInputStream(socket.getInputStream()));
                Object obj = is.readObject();
                if (obj != null) {
                    user = (User)obj;
                    System.out.println("user: " + user.getName() + "/" + user.getPassword());
                }
            } catch(IOException ex) {

5.如果還需要傳送時壓縮流再傳送，就要用到GZIPInputStream和GZIPOutputStream進行壓縮和反壓縮
server的寫法

GZIPInputStream gzipis = null;
                ObjectInputStream ois = null;
                GZIPOutputStream gzipos = null;
                ObjectOutputStream oos = null;

                try {
                    gzipis = new GZIPInputStream(socket.getInputStream());
                    ois = new ObjectInputStream(gzipis);
                    gzipos = new GZIPOutputStream(socket.getOutputStream());
                    oos = new ObjectOutputStream(gzipos);

                    Object obj = ois.readObject();
                    User user = (User)obj;
                    System.out.println("user: " + user.getName() + "/" + user.getPassword());

                    user.setName(user.getName() + "_new");
                    user.setPassword(user.getPassword() + "_new");

                    oos.writeObject(user);
                    oos.flush();
                    gzipos.finish();
                } catch (IOException ex) {

client的寫法

Socket socket = null;
            GZIPOutputStream gzipos = null;
            ObjectOutputStream oos = null;
            GZIPInputStream gzipis = null;
            ObjectInputStream ois = null;

            try {
                socket = new Socket();
                SocketAddress socketAddress = new InetSocketAddress("localhost", 10000);
                socket.connect(socketAddress, 10 * 1000);
                socket.setSoTimeout(10 * 1000);

                gzipos = new GZIPOutputStream(socket.getOutputStream());
                oos = new ObjectOutputStream(gzipos);
                User user = new User("user_" + i, "password_" + i);
                oos.writeObject(user);
                oos.flush();
                gzipos.finish();

                gzipis = new GZIPInputStream(socket.getInputStream());
                ois = new ObjectInputStream(gzipis);
                Object obj = ois.readObject();
                if (obj != null) {
                    user = (User)obj;
                    System.out.println("user: " + user.getName() + "/" + user.getPassword());
                }
            } catch(IOException ex) {

6.如果要加密傳送，就要使用加密後的socket，而不是使用加密的流

server的寫法，只需要對socket進行處理，流的處理不變

ServerSocketFactory factory = SSLServerSocketFactory.getDefault();
            ServerSocket server = factory.createServerSocket(10000);

client的寫法

SocketFactory factory = SSLSocketFactory.getDefault();
                socket = factory.createSocket("localhost", 10000);

使用加密技術，需要用到keystore文件

keytool -genkey -alias mysocket -keyalg RSA -keystore mysocket.jks 

7.使用nio實現socket通信

java.nio包是Java在1.4之後增加的，用來提高I/O操作的效率。在nio包中主要包括以下幾個類或接口:

* Buffer：緩衝區，用來臨時存放輸入或輸出數據。

* Charset：用來把Unicode字符編碼和其它字符編碼互轉。

* Channel：數據傳輸通道，用來把Buffer中的數據寫入到數據源，或者把數據源中的數據讀入到Buffer。

* Selector：用來支持異步I/O操作，也叫非阻塞I/O操作。

把對象轉爲字節數組

public static byte[] toBytes(Object object) {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        ObjectOutputStream oos = null;
        try {
            oos = new ObjectOutputStream(baos);
            oos.writeObject(object);
            byte[] bytes = baos.toByteArray();
            return bytes;

吧字節數組轉爲對象

 ByteArrayInputStream bais = new ByteArrayInputStream(bytes);
        ObjectInputStream ois = null;
        try {
            ois = new ObjectInputStream(bais);
            Object object = ois.readObject();
            return object;

server端的寫法

Selector selector = null;
        ServerSocketChannel serverSocketChannel = null;
        try {
            selector = Selector.open();
            serverSocketChannel = ServerSocketChannel.open();
            serverSocketChannel.configureBlocking(false);
            serverSocketChannel.socket().setReuseAddress(true);
            serverSocketChannel.socket().bind(new InetSocketAddress(10000));
            serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
            while (selector.select() > 0) {
                Iterator<SelectionKey> it = selector.selectedKeys().iterator();
                while (it.hasNext()) {
                    SelectionKey readyKey = it.next();
                    it.remove();
                    execute((ServerSocketChannel) readyKey.channel());
 


private static void execute(ServerSocketChannel serverSocketChannel) throws IOException {
        SocketChannel socketChannel = null;
        try {
            socketChannel = serverSocketChannel.accept();
            MyRequestObject myRequestObject = receiveData(socketChannel);
            logger.log(Level.INFO, myRequestObject.toString());

            MyResponseObject myResponseObject = new MyResponseObject(
                    "response for " + myRequestObject.getName(),
                    "response for " + myRequestObject.getValue());
            sendData(socketChannel, myResponseObject);

 MyRequestObject myRequestObject = null;
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        ByteBuffer buffer = ByteBuffer.allocate(1024);

        try {
            byte[] bytes;
            int size = 0;
            while ((size = socketChannel.read(buffer)) >= 0) {
                buffer.flip();
                bytes = new byte[size];
                buffer.get(bytes);
                baos.write(bytes);
                buffer.clear();
            }
            bytes = baos.toByteArray();
            Object obj = SerializableUtil.toObject(bytes);
            myRequestObject = (MyRequestObject)obj;

 sendData(SocketChannel socketChannel, MyResponseObject myResponseObject) throws IOException {
        byte[] bytes = SerializableUtil.toBytes(myResponseObject);
        ByteBuffer buffer = ByteBuffer.wrap(bytes);
        socketChannel.write(buffer);

client的寫法

socketChannel = SocketChannel.open();
                SocketAddress socketAddress = new InetSocketAddress("localhost", 10000);
                socketChannel.connect(socketAddress);

                MyRequestObject myRequestObject = new MyRequestObject("request_" + idx, "request_" + idx);
                logger.log(Level.INFO, myRequestObject.toString());
                sendData(socketChannel, myRequestObject);

                MyResponseObject myResponseObject = receiveData(socketChannel);
                logger.log(Level.INFO, myResponseObject.toString());

 private void sendData(SocketChannel socketChannel, MyRequestObject myRequestObject) throws IOException {
            byte[] bytes = SerializableUtil.toBytes(myRequestObject);
            ByteBuffer buffer = ByteBuffer.wrap(bytes);
            socketChannel.write(buffer);
            socketChannel.socket().shutdownOutput();


private MyResponseObject receiveData(SocketChannel socketChannel) throws IOException {
            MyResponseObject myResponseObject = null;
            ByteArrayOutputStream baos = new ByteArrayOutputStream();

            try {
                ByteBuffer buffer = ByteBuffer.allocateDirect(1024);
                byte[] bytes;
                int count = 0;
                while ((count = socketChannel.read(buffer)) >= 0) {
                    buffer.flip();
                    bytes = new byte[count];
                    buffer.get(bytes);
                    baos.write(bytes);
                    buffer.clear();
                }
                bytes = baos.toByteArray();
                Object obj = SerializableUtil.toObject(bytes);
                myResponseObject = (MyResponseObject) obj;
                socketChannel.socket().shutdownInput();
return myResponseObject;

上面的例子都需要先運行server再運行client。