java achieve socket chat

java.io.IOException Import; 
Import a java.io.InputStream; 
Import a java.io.OutputStream; 
Import the java.net.Socket; 
Import java.util.Scanner; 


public class Client { 
    the Socket Socket; 
    Private Final static int message_size = 1024; // maximum length allowed per data receiving 

    public static void main (String [] args) { 
        new new Client (); 
    } 

    public Client () { 
        the try { 
            Socket new new = the Socket ( "127.0.0.1", 45678); 
            IF ( socket.isConnected () == to true) { 
                System.out.println ( "connection successful"); 
                new new the thread () {// open a thread to accept data 
                    @Override 
                    public void RUN () { 
                        super.run ();
                        InputStream in;
                        try {
                            in = socket.getInputStream();
                            byte[] b;
                            while (true) {
                                b = new byte[MESSAGE_SIZE];
                                in.read(b);
                                System.out.println("接收到服务端消息：" + new String(b));
                            }
                        } catch (IOException e) {
                            e.printStackTrace();
                        }

                    }
                }.start();
            }
            OutputStream out = null;
            while (true) {
                Scanner scanner = new Scanner(System.in);
                String str = scanner.nextLine();
                out = socket.getOutputStream();
                out.write(str.getBytes());
                out.flush();
                if (str.equals("end")) {
                    System.exit(0);//关闭客户端
                }
            }

        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

java.io.IOException Import; 
Import a java.io.InputStream; 
Import the java.net.ServerSocket; 
Import the java.net.Socket; 
Import of java.util.ArrayList; 
Import java.util.List; 



public class Server { 

    List <ReceiveThread> receiveList = new ArrayList <> () ; // store connected client class 
    private final static int mESSAGE_SIZE = 1024; // maximum length of each accepted data allows 
    int num = 0; // client ID 

    public static void main ( String [] args) { 
        new new Server (); 
    } 

    // end service processing logic 
    Server () { 
        the serverSocket serverSocket = null; 
        the try { 
            serverSocket the serverSocket new new = (45678); // for listening socket port number designated 
            while (true) {
                Socket socket = serverSocket.accept (); // listen for client connections, blocked thread 
                System.out.println ( "client connection:" + NUM); 
// receiving a message from a client process in the other thread 
                ReceiveThread receiveThread = new receiveThread (socket, NUM); 
                receiveThread.start (); 
                receiveList.add (receiveThread); 

                // there is a new on-line client, the server notifies other clients 
                String notice = "new client on the line, now online clients are: client: "; 
                for (ReceiveThread Thread: receiveList) { 
                    Notice Notice = +" "+ thread.num; 
                } 
                for (ReceiveThread Thread: receiveList) { 
                    new new SendThread (thread.socket, Notice) .start ();
                }
                ++ NUM; 
            } 
        } the catch (IOException E) { 
            e.printStackTrace (); 
        } 
    } 


    // accept message thread (also corresponding to the recording action of the client socket) 
    class ReceiveThread the extends the Thread { 
        int NUM; 
        the Socket socket; // client corresponding socket 
        boolean continueReceive = true; // identifying whether further need to maintain the connection receiving 

        public ReceiveThread (the socket socket, int NUM) { 
            this.socket = socket; 
            this.num NUM =; 
            the try { 
                // the client is connected to the sends, client ID assignment notification 
                . socket.getOutputStream () write (( "your client ID is" NUM +) .getBytes ()); 
            } the catch (IOException E) {
                e.printStackTrace (); 
            } 
        } 

        @Override 
        public void RUN () { 
            super.run (); 
            // receiving the client message sent by 
            the InputStream inputStream = null; 
            the try { 
                inputStream Socket.getInputStream = (); 
                byte [] B; 
                the while (continueReceive) { 
                    B = new new byte [message_size]; 
                    InputStream.read (B); 
                    B = splitByte (B); // remove unnecessary portions array 
                    // transmitting end client disconnects 
                    if (new String (b) .equals ( "End")) { 
                        continueReceive = to false;
                        receiveList.remove (the this); 
                        // notify other clients 
                        + NUM + "Disconnect \ n" String message = "client" + 
                                "are now online, the client:"; 
                        for (ReceiveThread receiveThread: receiveList) { 
                            + = Message Message "" + receiveThread.num; 
                        } 
                        System.out.println (Message); 
                        for (receiveThread receiveThread: receiveList) { 
                            new new SendThread (receiveThread.socket, Message) .start (); 
                        } 
                    } {the else 
                        the try {
                            String [] data = new String ( b) .split ( "", 2); // with the first space, the character string divided into two parts 
                            int clientNum = Integer.parseInt (data [0 ]); // convert digital, i.e. the client ID number 
                            // sends a message to the specified client 
                            for (ReceiveThread receiveThread: receiveList) { 
                                IF (receiveThread.num == clientNum) { 
                                    new new SendThread (receiveThread.socket, "client" + num + " message: "Data + [. 1]) Start ();. 
                                    System.out.println (" client "+ num +" sends a message to the client "+ receiveThread.num +": "+ data [1]);
                                }
                            }
                        } catch (Exception e) {
                            new SendThread (socket, "input error, please re-enter") .start (); 
                            System.out.println ( "Client input error"); 
                        } 

                    } 
                } 
            } the catch (IOException E) { 
                e.printStackTrace (); 
            } {the finally 
                the try {// Close the resource 
                    IF (inputStream = null!) { 
                        inputStream.close (); 
                    } 
                    IF (Socket = null!) { 
                        the Socket.close (); 
                    } 
                } the catch (IOException E) { 
                    e.printStackTrace () ;
                } 
            } 
        } 
    } 

    // Send message thread 
    class the extends the Thread {SendThread 
        the Socket Socket; 
        String STR; 

        public SendThread (the Socket Socket, String STR) { 
            this.socket = Socket; 
            this.str STR =; 
        } 

        @Override 
        public void RUN ( ) { 
            super.run (); 
            the try { 
                Socket.getOutputStream () Write (str.getBytes (.)); 
            } the catch (IOException E) { 
                e.printStackTrace (); 
            } 

        } 
    } 

    // remove excess portions of the byte array
    private byte[] splitByte(byte b[]) {
        int i = 0;
        for (; i < b.length; i++) {
            if (b[i] == 0) {
                break;
            }
        }
        byte[] b2 = new byte[i];
        for (int j = 0; j < i; j++) {
            b2[j] = b[j];
        }
        return b2;
    }

}