Java Client Server Demo using Socket

ClientSide.java

package com.hieunv.ltht;

import java.io.*;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.Date;
import java.util.Scanner;

import static java.net.InetAddress.getByName;

/**
 * Created by HieuNguyen on 02/25/2017.
 */
public class ClientSide {
    public static void main(String[] args) {

        // Địa chỉ máy chủ.
        String serverHost = "localhost";
        int port = 80;
        Socket socketOfClient = null;
        BufferedWriter os = null;
        BufferedReader is = null;

        Scanner sc = new Scanner(System.in);


        try {
                try {
                    System.out.println("Enter serverHost: ");
                    serverHost = sc.nextLine();
                    System.out.println("Enter port: ");
                    port = sc.nextInt();
                    socketOfClient = new Socket(serverHost, port);
                } catch (IOException e) {
                    System.out.println("Error when connect to serverHost, try again");
                }
            os = new BufferedWriter(new OutputStreamWriter(socketOfClient.getOutputStream()));

            is = new BufferedReader(new InputStreamReader(socketOfClient.getInputStream()));

        } catch (UnknownHostException e) {
            System.err.println("Don't know about host " + serverHost);
            return;
        } catch (IOException e) {
            System.err.println("Couldn't get I/O for the connection to " + serverHost);
            return;
        }
        System.out.println("Connect to "+serverHost+":"+port+" success!");
        try {
            while (true) {
                System.out.println("\nMENU");
                System.out.println("1.Giai PTB2");
                System.out.println("2.Giai PT bac nhat hai an");
                System.out.println("3.Exit");
                System.out.println("Your choice: ");
                int ch;
                do{
                    ch = sc.nextInt();
                    if(ch < 1 || ch > 3){
                        System.out.println("Try again: ");
                    }
                }while (ch < 1 || ch > 3);
                if(ch == 1){
                    System.out.println("Enter value a,b,c follow syntax \"a b c\" : ");
                    sc.nextLine();
                    String s =sc.nextLine();
                    os.write("1 "+s);
                    os.newLine();
                    os.flush();
                }else if(ch == 2){
                    System.out.println("Enter value a1,b1,c1,a2,b2,c2 follow syntax \"a1 b1 c1 a2 b2 c2\" : ");
                    sc.nextLine();
                    String s =sc.nextLine();
                    os.write("2 "+s);
                    os.newLine();
                    os.flush();
                }else{
                    os.write("EXIT");
                    os.flush();
                    System.out.println("Connect is lost!");
                   break;
                }
                System.out.println(is.readLine());
            }
            os.close();
            is.close();
            socketOfClient.close();
        } catch (UnknownHostException e) {
            System.err.println("Trying to connect to unknown host: " + e);
        } catch (IOException e) {
            System.err.println("IOException:  " + e);
        }
    }
}

ServerSide.java

package com.hieunv.ltht;

import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Scanner;

/**
 * Created by HieuNguyen on 02/25/2017.
 */
public class ServerSide {
    public static void main(String args[]) throws IOException {

        ServerSocket listener = null;

        int clientNumber = 0;

        try {
            listener = new ServerSocket(7777);
        } catch (IOException e) {
            System.out.println(e);
            System.exit(0);
        }

        System.out.println("Server is waiting to accept user...");
        try {
            while (true) {
                Socket socketOfServer = listener.accept();
                new ServiceThread(socketOfServer, clientNumber++).start();
            }
        } finally {
            listener.close();
        }

    }

    private static void log(String message) {
        System.out.println(message);
    }

    private static class ServiceThread extends Thread {

        private int clientNumber;
        private Socket socketOfServer;

        public ServiceThread(Socket socketOfServer, int clientNumber) {
            this.clientNumber = clientNumber;
            this.socketOfServer = socketOfServer;
            log("New connection with client# " + this.clientNumber + " at " + socketOfServer);
        }

        private String giaiPTB1(double a1,double b1,double c1,double a2,double b2, double c2){
            String rs = "";
            double D,Dx,Dy;
            D=a1*b2-a2*b1; Dx=c1*b2-c2*b1; Dy=a1*c2-a2*c1;
            if(D == 0){
                if(Dx == 0 && Dy == 0){
                    rs = "PT bac nhat co vo so nghiem!";
                }else{
                    rs = "PT bac nhat vo nghiem!";
                }
            }else{
                rs = "PT bac nhat co nghiem duy nhat (x,y) = (" + (Dx/D)+","+(Dy/D)+")";
            }
            return rs;
        }


        private String giaiPTB2(double a, double b, double c){
            String result = "";
            if(a == 0){
                if(b == 0){
                    if(c == 0){
                        result += "Phuong trinh bac nhat(a = 0) co vo so nghiem!";
                    }else{
                        result += "Phuong trinh bac nhat(a = 0) vo nghiem!";
                    }
                }else{
                    result += "Phuong trinh bac nhat(a = 0) co nghiem: x = " + (-c/b);
                }
            }else{
                double delta = b*b - a*c*4;
                if(delta < 0){
                    result += "Phuong trinh bac hai vo nhgiem!";
                }else if(delta == 0){
                    result += "Phuong trinh bac hai co ngiem kep x1 = x2 = " + (-b/(2*a));
                }else{
                    result += "Phuong trinh bac hai co 2 nghiem phan biet: x1 = " + (-b + Math.sqrt(delta))/(2*a) + ", x2 = " + (-b - Math.sqrt(delta))/(2*a);
                }
            }
            return  result;
        }

        @Override
        public void run() {

            try {

                BufferedReader is = new BufferedReader(new InputStreamReader(socketOfServer.getInputStream()));
                BufferedWriter os = new BufferedWriter(new OutputStreamWriter(socketOfServer.getOutputStream()));

                while (true) {
                    String line = is.readLine();
                    if(line == null) continue;
                    if(line.equals("EXIT")){
                        log("Lost connection of client# " + this.clientNumber + " at " + socketOfServer);
                        log("Server still listening client request...");
                    }else{
                        String s[] = line.trim().split(" ");
                        int ch = 0;
                        double a,b,c;
                        try{
                            ch = Integer.parseInt(s[0]);
                            a = Double.parseDouble(s[1]);
                            b = Double.parseDouble(s[2]);
                            c = Double.parseDouble(s[3]);
                            String result = "Server: ";
                            if(ch == 1){
                                result += giaiPTB2(a,b,c);
                            }else{
                                double a1 = Double.parseDouble(s[4]);
                                double b1 = Double.parseDouble(s[5]);
                                double c1 = Double.parseDouble(s[6]);
                                result += giaiPTB1(a,b,c,a1,b1,c1);
                            }

                            os.write(result);
                            os.newLine();
                            os.flush();
                        }catch (Exception e){
                            os.write("Server: Input is error!");
                            os.newLine();
                            os.flush();
                        }
                    }
                }

            } catch (IOException e) {
                System.out.println(e);
            }
        }
    }


}