Socket Authentication Server?

Question

I am currently playing with java to create an authentication server for a desktop application, and so far I have managed to start both the client and the server as a chat server / client to run.

I understand that I have only a small part of the work, and there are many things that need to be found, and to find out, but right now at this stage I am wondering how authentication is done.

For example, this is server code:

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;

public class LoginServer
{
    public static void main(String[] args) throws Exception {
        int port = 7000;
        int id = 1;

        ServerSocket loginserver = null;
        try
        {
            loginserver = new ServerSocket(port);
            System.out.println("LoginServer started...");
        }
        catch (IOException e) {
            System.out.println("Could not listen on port: " + port);
            System.exit(-1);
        }

        while (true)
        {
            Socket clientSocket = loginserver.accept();
            ClientServiceThread cliThread = new ClientServiceThread(clientSocket, id++);
            cliThread.start();
        }
    }
}

class ClientServiceThread extends Thread
{
    Socket clientSocket;
    int clientID = -1;
    boolean running = true;

    ClientServiceThread(Socket s, int i)
    {
        clientSocket = s;
        clientID = i;
    }

    public void run()
    {
        System.out.println("Accepted Client : ID - " + clientID + " : Address - " + clientSocket.getInetAddress().getHostName());
        try
        {
            BufferedReader   in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
            PrintWriter   out = new PrintWriter(new OutputStreamWriter(clientSocket.getOutputStream()));
            while (running)
            {
                String clientCommand = in.readLine();
                System.out.println("Client Says :" + clientCommand);
                if (clientCommand.equalsIgnoreCase("quit"))
                {
                    running = false;
                    System.out.print("Stopping client thread for client : " + clientID);
                }
                else
                {
                    out.println(clientCommand);
                    out.flush();
                }
            }
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }
    }
}

As you can see, I read that the client sends and displays to the console, and also checks whether the client sent the quit or not command.

• I am wondering how I would do this so that the client can only connect to him if the user and password were sent?

• , , 3 ?

• ?

Answer 1

, .

, , , . , .

, . quit, , .

:

String line;
while ((line = in.readLine()) != null) {
    switch (state) {
        case login:
            processLogin(line);
            break;
        case command:
            processCommand(line);
            break;
    }
}

processLogin :

void processLogin(String line) {
    if (user == null) {
        user = line;
    }
    else if (password == null) {
        password = line;
    }
    else {
        if (validUser(user, password)) {
            state = command;
        }
        else {
            socket.close();
        }
    }
}

processCommand:

void processCommand(String line) {
    if (line.equals(...)) {
        // Process each command like this
    }
    else if (line.equals("quit")) {
        socket.close();
    }
    else {
        System.err.println("Unrecognized command: " + line);
    }
}

state, , . , . , .