public class ServerDemo {

    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = new ServerSocket(8888);
        System.out.println("Server started with port number 8888...");
        while (true) {
            Socket socket = serverSocket.accept();
            System.out.println("有新客户端接入。。。");
            Boolean isOff = false;
            new Thread(new Runnable() {
                Socket s;
                Boolean isOff;

                Runnable setSocket(Socket s,Boolean isOff) {
                    this.s = s;
                    this.isOff = isOff;
                    return this;
                }

                @Override
                public void run() {
                    InputStream inputStream;
                    try {
                        inputStream = s.getInputStream();
                        try(BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream))){
                            String line;
                            while (!isOff && (line = reader.readLine()) != null) {
                                System.out.println("client:"+ line);
                            }
                        }
                    } catch (Exception e) {
                        System.out.println("server 已退出通信！");
                    } finally {
                        if(s != null){
                            try {
                                s.close();
                            } catch (IOException e) {
                                e.printStackTrace();
                            }
                        }
                    }
                }
            }.setSocket(socket,isOff)).start();


            new Thread(new Runnable() {
                Socket s;
                Boolean isOff;

                Runnable setSocket(Socket s,Boolean isOff) {
                    this.s = s;
                    this.isOff = isOff;
                    return this;
                }

                @Override
                public void run() {
                    Scanner scanner = new Scanner(System.in);
                    String line;
                    OutputStream outputStream = null;
                    try {
                        outputStream = s.getOutputStream();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                    try (BufferedOutputStream writer = new BufferedOutputStream(outputStream)) {
                        while (!isOff &&  !(line = scanner.nextLine()).equals("exit") ) {
                            line += "\n";
                            writer.write(line.getBytes(StandardCharsets.UTF_8));
                            writer.flush();
                        }
                        writer.write("\nGoodbye! client!".getBytes(StandardCharsets.UTF_8));
                        writer.flush();
                        isOff = true;
                    } catch (IOException e) {
                        System.out.println("server 已退出通信！");
                    } finally {
                        if(s != null){
                            try {
                                s.close();
                            } catch (IOException e) {
                                e.printStackTrace();
                            }
                        }
                    }

                }
            }.setSocket(socket,isOff)).start();
        }


    }


}

• 客户端代码：

public class ClientDemo {

    public static void main(String[] args) throws IOException {
        Socket socket = new Socket("127.0.0.1",8888);
        Boolean isOff = false;
        System.out.println("Server connected successfully...");

        new Thread(new Runnable() {
            Socket s;
            Boolean isOff;

            Runnable setSocket(Socket s,Boolean isOff) {
                this.s = s;
                this.isOff = isOff;
                return this;
            }

            @Override
            public void run() {
                Scanner scanner = new Scanner(System.in);
                String line;
                OutputStream outputStream;
                try {
                    outputStream = s.getOutputStream();
                    try (BufferedOutputStream writer = new BufferedOutputStream(outputStream)) {
                        while (!(line = scanner.nextLine()).equals("exit")) {
                            line += "\n";
                            writer.write(line.getBytes(StandardCharsets.UTF_8));
                            writer.flush();
                        }
                        writer.write("\nGoodbye! server!".getBytes(StandardCharsets.UTF_8));
                        writer.flush();
                        isOff = true;
                    } catch (Exception e) {
                        System.out.println("client 已退出通信！");
                    }finally {
                        if(s != null){
                            try {
                                s.close();
                            } catch (IOException e) {
                                e.printStackTrace();
                            }
                        }
                    }
                }catch (Exception e) {
                        System.out.println("client 已退出通信！");
                }
            }
        }.setSocket(socket,isOff)).start();

        new Thread(new Runnable() {
            Socket s;
            Boolean isOff;

            Runnable setSocket(Socket s,Boolean isOff) {
                this.s = s;
                this.isOff = isOff;
                return this;
            }

            @Override
            public void run() {
                InputStream inputStream;
                try {
                    inputStream = socket.getInputStream();
                    try (BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream))) {
                        String line;
                        while ((line = bufferedReader.readLine()) != null && !isOff){
                            System.out.println("server:"+line);
                        }
                    }
                } catch (IOException e) {
                    System.out.println("通信已经关闭了！");
                }
            }
        }.setSocket(socket,isOff)).start();
    }
}