一、TCP的相关IP

1.1 SeverSocket

这是Socket类,对应到网卡,但是这个类只能给服务器使用.

1.2 Socket

对应到网卡,既可以给服务器使用,又可以给客户端使用.

TCP是面向字节流的,传输的基本单位是字节.

TCP是有连接的,和打电话一样,需要客户端拨号,服务器来听.

服务器的内核会配合客户端这边的工作,来完成连接的建立.

这个连接建立的过程,就相当于电话这边在拨号,另外一边就在响铃.

但是需要等待用户点击了接听,才能进行后续通信.

内核建立的连接不是决定性的,还需要用户程序,把这个程序进行 "接听"/ accept 操作,然后才能进行后续的通信.

accept也是一个可能会产生阻塞的操作,如果当前没有客户端连过来,此时accept就会阻塞.

有一个客户端连过来了,accept一次就能返回一次

有若干个客户端连过来了,accept就需要执行多次.

二、实现TCP回显服务器

2.1 服务器代码

private ServerSocket serverSocket = null;
    public TcpEchoServer(int port) throws IOException {
        serverSocket = new ServerSocket(port);
    }
    public void start() throws IOException {
        System.out.println("服务器启动");
        ExecutorService pool = Executors.newCachedThreadPool();
        while(true){
            Socket clientSocket = serverSocket.accept();
            //Thread t = new Thread(()->{
            //    processConnection(clientsocket);
            //});
            //t.start();
            pool.submit(new Runnable() {
                @Override
                public void run() {
                    try {
                        processConnection(clientSocket);
                    } catch (IOException e) {
                        throw new RuntimeException(e);
                    }
                }
            });
        }
    }
    private void processConnection(Socket clientSocket) throws IOException {
        System.out.printf("[%s:%d] 客户端上线!\n",clientSocket.getInetAddress(),clientSocket.getPort());
        try(InputStream inputStream = clientSocket.getInputStream();
            OutputStream outputStream = clientSocket.getOutputStream()){
            while(true){
                Scanner scanner = new Scanner(inputStream);
                if(!scanner.hasNext()){
                    System.out.printf("[%s:%d] 客户端下线",clientSocket.getInetAddress(),clientSocket.getPort());
                    break;
                }

                String resquest = scanner.next();
                String response = process(resquest);
                PrintWriter printWriter = new PrintWriter(outputStream);
                printWriter.println(response);
                printWriter.flush();

                System.out.printf("[%s;%d] req: %s,resp: %s\n",clientSocket.getInetAddress(),clientSocket.getPort(),
                        resquest,response);
            }
        } catch (IOException e) {
            throw new RuntimeException(e);
        }finally {
            clientSocket.close();
        }
    }

    public String process(String request){
        return request;
    }

    public static void main(String[] args) throws IOException {
        TcpEchoServer sever = new TcpEchoServer(9090);
        sever.start();
    }

2.2 客户端代码

private Socket socket = null;
    public TcpEchoClient(String severIp,int severPort) throws IOException {
        socket = new Socket(severIp,severPort);
    }

    public void start(){
        System.out.println("客户端启动");
        try(InputStream inputStream =socket.getInputStream();
            OutputStream outputStream = socket.getOutputStream()) {
            Scanner scannerConsole = new Scanner(System.in);
            Scanner scannerNetwoek = new Scanner(inputStream);
            PrintWriter writer = new PrintWriter(outputStream);
            while(true){
                //1.从控制台读取字符
                System.out.println("->");
                if(!scannerConsole.hasNext()){
                    break;
                }
                String request = scannerConsole.next();
                //2.把请求发给服务器
                 writer.println(request);
                 writer.flush();
                 //3.从服务器读取响应
                String response = scannerNetwoek.next();
                //4.把响应打印出来
                System.out.println(response);
            }
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }

    public static void main(String[] args) throws IOException {
        TcpEchoClient client = new TcpEchoClient("127.0.0.1",9090);
        client.start();
    }