目錄

基本概念

發(fā)送端與接收端

請(qǐng)求與響應(yīng)

?編輯客戶端與服務(wù)器

Socket套接字?

分類

數(shù)據(jù)報(bào)套接字

流套接字傳輸模型??

UDP數(shù)據(jù)報(bào)套接字編程

DatagramSocket API

DatagramPacket API

InetSocketAddress API

示例一:

示例二:

TCP流數(shù)據(jù)報(bào)套接字編程

ServerSocket API

Socket API

示例一:

?

網(wǎng)絡(luò)編程指的是,網(wǎng)絡(luò)上的主機(jī)的不同進(jìn)程通過編程的方式實(shí)現(xiàn)網(wǎng)絡(luò)通信.同一主機(jī)下只要滿足不同進(jìn)程間的通信就可以成為"網(wǎng)絡(luò)通信"

基本概念

發(fā)送端與接收端

在網(wǎng)絡(luò)通信中:

作為發(fā)送數(shù)據(jù)的進(jìn)程稱為"發(fā)送端",發(fā)送端主機(jī)即網(wǎng)絡(luò)通信中的"源主機(jī)"?

作為接收數(shù)據(jù)的進(jìn)程稱為"接收端",接收端主機(jī)即網(wǎng)絡(luò)通信中的"目的主機(jī)"

注意:網(wǎng)絡(luò)通信中的發(fā)送端與接收端都是相對(duì)的.

請(qǐng)求與響應(yīng)

一般來說,一次網(wǎng)絡(luò)通信中設(shè)計(jì)到兩次數(shù)據(jù)傳輸:

• 第一次:A端向B端發(fā)送的請(qǐng)求
• 第二次:B端向A端發(fā)送的響應(yīng)

客戶端與服務(wù)器

服務(wù)器:在網(wǎng)絡(luò)通信下,提供服務(wù)的一端.(服務(wù)可以指:響應(yīng)一定的要求)

客戶端:獲取服務(wù)的一端

Socket套接字?

Socket套接字，是由系統(tǒng)提供用于網(wǎng)絡(luò)通信的技術(shù),是基于TCP/IP協(xié)議的網(wǎng)絡(luò)通信的基本操作單元.基于Socket套接字的網(wǎng)絡(luò)程序開發(fā)就是網(wǎng)絡(luò)編程.

分類

套接字根據(jù)傳輸層協(xié)議主要分成:

• 數(shù)據(jù)報(bào)套接字:使用傳輸層UDP協(xié)議(User Datagram Protocol)用戶數(shù)據(jù)報(bào)協(xié)議
• 流套接字:使用傳輸層TCP協(xié)議(Transmission Control Protocol)傳輸層控制協(xié)議
• 原始套接字:用于自定義傳輸層協(xié)議

數(shù)據(jù)報(bào)套接字

數(shù)據(jù)報(bào)固定每次傳輸?shù)淖止?jié),更像是寫信,有來有回的.

流套接字傳輸模型??

面對(duì)的是字節(jié)流.

打電話一般,接通后就可以無節(jié)制的傳輸.

UDP數(shù)據(jù)報(bào)套接字編程

DatagramSocket API

構(gòu)造方法

常用方法?

DatagramPacket API

構(gòu)造方法

常用方法?

InetSocketAddress API

InetSocketAddress是ScketAddress的一個(gè)子類,用來包裝IP與端口號(hào)

示例一:

客戶端像服務(wù)器發(fā)出請(qǐng)求,但服務(wù)器無響應(yīng)版本

服務(wù)器:

public class UdpServer {

    private DatagramSocket socket= null;

    public UdpServer(int port) throws SocketException {//構(gòu)造方法
        this.socket = new DatagramSocket(port);
    }

    public void start() throws IOException {//作為啟動(dòng)服務(wù)器的方法
        while(true){//因?yàn)椴恢朗裁磿r(shí)候客戶端會(huì)發(fā)送請(qǐng)求
            //作為服務(wù)器,需要不停的接收客戶端的請(qǐng)求
            //創(chuàng)建packet
            byte[] bytes = new byte[1024];
            DatagramPacket packet = new DatagramPacket(bytes,bytes.length);//用bytes作為接收,使用的長(zhǎng)度為bytes的長(zhǎng)度

            System.out.println("等待接收數(shù)據(jù)中...");
            socket.receive(packet);//還沒收到之前會(huì)進(jìn)行阻塞等待
            //此處的版本沒有作出響應(yīng)
            //我們可以打印出收到的packet中的數(shù)據(jù)看看有什么東西

            System.out.println("IP: " + packet.getAddress().getHostAddress());
            System.out.println("端口號(hào): " + packet.getPort());
            System.out.printf("文本數(shù)據(jù)為: " + new String(packet.getData()));
            System.out.println("原始數(shù)據(jù)為: " + Arrays.toString(packet.getData()));
        }
    }
    public static void main(String[] args) throws IOException {
        UdpServer udpServer = new UdpServer(1024);
        udpServer.start();
    }
}

客戶端:

方法一:
public class UdpClient {
    public static void main(String[] args) throws IOException {
        //創(chuàng)建Socket
        DatagramSocket socket = new DatagramSocket();//創(chuàng)建一個(gè)socket,端口號(hào)為系統(tǒng)隨機(jī)分配
        //構(gòu)建Packet
        byte[] bytes = "Hello World".getBytes();//字符串轉(zhuǎn)換成byte再塞進(jìn)數(shù)組
        SocketAddress address = new InetSocketAddress("localhost",1024);//目的IP為本地地址,端口號(hào)為1024
        DatagramPacket packet = new DatagramPacket(bytes,bytes.length,address);//構(gòu)建packet
        socket.send(packet);//發(fā)送
        System.out.println("發(fā)送完成");
    }
}
方法二:
public class UdpClient {
    private DatagramSocket socket = null;//socket
    private String serverIp;
    private int serverPort;

    public UdpClient(String serverIp,int serverPort) throws SocketException {
        this.socket = new DatagramSocket();
        this.serverIp = serverIp;
        this.serverPort = serverPort;
    }

    public void start() throws IOException {
        System.out.println("客戶端啟動(dòng)");
        Scanner scanner = new Scanner(System.in);
        while(true){
            System.out.println("輸入:");
            String text = scanner.next();
            if(text.equals("exit")){
                System.out.println("再見");
                break;
            }
            //需要用InetAddress將字符串鐘的IP轉(zhuǎn)換成地址形式
            //SocketAddress address = new InetSocketAddress("localhost",1024);//也可以創(chuàng)建一個(gè)實(shí)例進(jìn)行包裝IP與端口號(hào)
            //此處的長(zhǎng)度是字節(jié)的長(zhǎng)度噢,注意單位
            DatagramPacket packet = new DatagramPacket(text.getBytes(),text.getBytes().length,InetAddress.getByName(serverIp),serverPort);
            socket.send(packet);
            System.out.println("發(fā)送成功");
        }
    }
    public static void main(String[] args) throws IOException {
        UdpClient client = new UdpClient("127.0.0.1",1024);
        client.start();
    }

先啟動(dòng)服務(wù)器后啟動(dòng)客戶端發(fā)送.

記得打開IDEA可以同時(shí)運(yùn)行兩個(gè)進(jìn)程的選項(xiàng)噢!

服務(wù)器接收到的信息為:

示例二:

做一個(gè)服務(wù)器對(duì)客戶端有響應(yīng)的版本

簡(jiǎn)單的英漢翻譯

服務(wù)器:

public class UdpServerResponse{
    private DatagramSocket socket= null;

    public UdpServerResponse(int port) throws SocketException {//構(gòu)造方法
        this.socket = new DatagramSocket(port);
    }

    public void start() throws IOException {//啟動(dòng)服務(wù)器
        while(true){
            byte[] bytes = new byte[1024];
            DatagramPacket receivePacket = new DatagramPacket(bytes,bytes.length);//創(chuàng)建包來接收

            System.out.println("等待接收數(shù)據(jù)中...");
            socket.receive(receivePacket);//接收包
            String request = new String(receivePacket.getData(),0,receivePacket.getLength());//根據(jù)接收到的包轉(zhuǎn)換成字符串
            String response = process(request);//對(duì)請(qǐng)求進(jìn)行分析
            //記得是getSocketAddress噢里面通常包含了IP與端口號(hào)
            DatagramPacket sendPacket = new DatagramPacket(response.getBytes(),response.getBytes().length,receivePacket.getSocketAddress());
            socket.send(sendPacket);//對(duì)客戶端作出響應(yīng)
            System.out.println("客戶端IP: " + receivePacket.getAddress());
            System.out.println("客戶端端口號(hào): " + receivePacket.getPort());
            System.out.println("收到的文本: " + request);
            System.out.println("返回的文本: " + response);
        }
    }

    public String process(String request){//解析請(qǐng)求,看看要做什么
        //這里就做一個(gè)英漢翻譯吧
        HashMap<String,String> map = new HashMap<>();
        map.put("人","human");
        map.put("貓","cat");
        map.put("狗","dog");
        return map.getOrDefault(request,"查閱失敗");
    }

    public static void main(String[] args) throws IOException {
        UdpServerResponse udpServerResponse = new UdpServerResponse(1024);
        udpServerResponse.start();
    }
}

客戶端:

public class UdpClientResponse {
    private DatagramSocket socket = null;
    private String serverIp;
    private int serverPort;

    public UdpClientResponse(String serverIp,int serverPort) throws SocketException {
        this.serverIp = serverIp;
        this.serverPort = serverPort;
        socket = new DatagramSocket();
    }

    public void start() throws IOException {
        System.out.println("客戶端啟動(dòng)");
        Scanner scanner = new Scanner(System.in);
        while (true) {
            System.out.print("輸入: ");
            String request = scanner.next();
            if(request.equals("exit")){
                System.out.println("再見!");
                break;
            }
            //根據(jù)請(qǐng)求創(chuàng)建包
            DatagramPacket sendPacket = new DatagramPacket(request.getBytes(),request.getBytes().length, InetAddress.getByName("127.0.0.1"),1024);
            socket.send(sendPacket);
            System.out.println("發(fā)送成功");
            DatagramPacket receivePacket = new DatagramPacket(new byte[1024],1024);//創(chuàng)建接收包
            socket.receive(receivePacket);
            String receive = new String(receivePacket.getData(),0,receivePacket.getLength());
            System.out.println(receive);
        }
    }

    public static void main(String[] args) throws IOException {
        UdpClientResponse udpClientResponse = new UdpClientResponse("127.0.0.1",1024);
        udpClientResponse.start();
    }
}

服務(wù)器的打印

客戶端的打印

TCP流數(shù)據(jù)報(bào)套接字編程

ServerSocket API

創(chuàng)建TCP服務(wù)端的API

構(gòu)造方法

方法

Socket API

用來建立鏈接后保存對(duì)方的信息

構(gòu)造方法:

常用方法?

在TCP協(xié)議中的連接還分為長(zhǎng)連接與短鏈接.

• 短連接：每次接收到數(shù)據(jù)并返回響應(yīng)后，都關(guān)閉連接，即是短連接。也就是說，短連接只能一次收發(fā)數(shù)據(jù)
• 長(zhǎng)連接：不關(guān)閉連接，一直保持連接狀態(tài)，雙方不停的收發(fā)數(shù)據(jù)，即是長(zhǎng)連接。也就是說，長(zhǎng)連接可以多次收發(fā)數(shù)據(jù)

示例一:

一請(qǐng)求一響應(yīng)

此處為長(zhǎng)連接(把代碼里的while(true)去掉就是短連接啦!只進(jìn)行一次請(qǐng)求響應(yīng))

服務(wù)器:

對(duì)于服務(wù)器來說,每次與客戶端連接后會(huì)創(chuàng)建一個(gè)socket來暫時(shí)存儲(chǔ)客戶端的信息數(shù)據(jù)

斷開連接后,記得要將這個(gè)存儲(chǔ)客戶端數(shù)據(jù)的socket進(jìn)行close釋放掉

在服務(wù)器進(jìn)程中,一個(gè)客戶端socket會(huì)占用文件描述符的一個(gè)位置,一個(gè)服務(wù)器可能會(huì)要與成千上萬個(gè)客戶端進(jìn)行通信,不釋放就會(huì)將文件描述符的位置沾滿造成泄露.

而服務(wù)器的serverSocket的生命周期與整個(gè)進(jìn)程相當(dāng),且只有一個(gè).所以可以不進(jìn)行釋放

使用線程池,用多線程的方式來運(yùn)行服務(wù)器達(dá)到同時(shí)與多個(gè)客戶端進(jìn)行通信的功能.

public class TcpServer {
    private ServerSocket socket = null;
     public TcpServer(int port) throws IOException {
         socket = new ServerSocket(port);
     }

     public void start() throws IOException {
         //嘗試鏈接
         ExecutorService threadPool = Executors.newCachedThreadPool();//創(chuàng)建一個(gè)線程池,一個(gè)線程對(duì)應(yīng)一個(gè)客戶端進(jìn)行通信
         while (true) {
             Socket clientSocket = socket.accept();//會(huì)阻塞等待接受
             threadPool.submit(() -> {//向線程提供任務(wù)
                 try {
                     processConnect(clientSocket);
                 } catch (IOException e) {
                     e.printStackTrace();
                 }
             });
         }
     }
     public void processConnect(Socket clientSocket) throws IOException {
         System.out.println("已與客戶端進(jìn)行鏈接-" + clientSocket.getInetAddress() + clientSocket.getPort());
         try(InputStream inputStream = clientSocket.getInputStream();
             OutputStream outputStream = clientSocket.getOutputStream()){
             while(true){
                 Scanner scanner = new Scanner(inputStream);//讀
                 PrintWriter printWriter = new PrintWriter(outputStream);//寫
                 if(!scanner.hasNext()){//客戶端不再傳輸數(shù)據(jù)就斷開鏈接
                     System.out.println("結(jié)束");
                     break;
                 }
                 String request = scanner.next();//接收請(qǐng)求
                 String response = process(request);//處理請(qǐng)求
                 printWriter.println(response);//向客戶端寫回響應(yīng)
                 printWriter.flush();//記得寫回后進(jìn)行刷新緩沖區(qū)
                 System.out.println("響應(yīng):" + clientSocket.getInetAddress() + clientSocket.getPort() + "文本: "+ response);
             }
         } catch (IOException e) {
             e.printStackTrace();
         }finally {
             clientSocket.close();//記得要關(guān)閉
         }
     }

     public String process(String request){
         HashMap<String,String> map = new HashMap<>();
         map.put("人","human");
         map.put("貓","cat");
         map.put("狗","dog");
         return map.getOrDefault(request,"查閱失敗");
     }

    public static void main(String[] args) throws IOException {
        TcpServer tcpServer = new TcpServer(1024);
        tcpServer.start();
    }
}

客戶端:

public class TcpClient {
    private Socket socket = null;
    private String serverIp;
    private int serverPort;

    public TcpClient(String serverIp,int serverPort) throws IOException {
        socket = new Socket(serverIp,serverPort);//客戶端隨機(jī)分配端口號(hào)
        this.serverIp = serverIp;
        this.serverPort = serverPort;
    }

    public void start(){
        try(InputStream inputStream = socket.getInputStream();
            OutputStream outputStream = socket.getOutputStream()) {
            //創(chuàng)建流對(duì)象進(jìn)行寫與讀
            while(true){
                Scanner scanner = new Scanner(System.in);//用來寫入
                PrintWriter printWriter = new PrintWriter(outputStream);//包裝output流對(duì)象
                String request = scanner.next();//寫請(qǐng)求
                if(request.equals("exit")){
                    System.out.println("結(jié)束與服務(wù)器連接");
                    break;
                }
                //把請(qǐng)求放到流對(duì)象中寫出去
                printWriter.println(request);
                printWriter.flush();//刷新緩沖區(qū)
                Scanner responseScanner = new Scanner(inputStream);
                String response = responseScanner.next();//讀服務(wù)器的響應(yīng)
                System.out.println(response);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) throws IOException {
        TcpClient tcpClient = new TcpClient("127.0.0.1",1024);
        tcpClient.start();
    }
}

服務(wù)器打印:

?

客戶端打印:

?

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