Example Java Socket Server

import java.lang.*;
import java.io.*;
import java.net.*;
import java.util.HashMap;
import java.util.Map;

public class SocketServer {

    private static final Map<String, String> USER_PASSWORD_MAP = new HashMap<String, String>();
    private static final String USER_PROMPT = "enter username";
    private static final String PASSWORD_PROMPT = "enter password";
    private static final String WELCOME_MESSAGE = "Welcome to My Server";
    private static final int MAX_LOGIN_FAILS = 3;

    static {
        USER_PASSWORD_MAP.put("1", "2");
        USER_PASSWORD_MAP.put("user", "password");
    }

    private static boolean authenticateUser(BufferedReader in, PrintWriter out) throws IOException {
        for (int i = 0; i < MAX_LOGIN_FAILS; i++) {
            out.println(USER_PROMPT);
            String userName = in.readLine();
            out.println(PASSWORD_PROMPT);
            String password = in.readLine();
            if (USER_PASSWORD_MAP.containsKey(userName) == true) {
                String userPassword = USER_PASSWORD_MAP.get(userName);
                if (password.equals(userPassword) == true) {
                    return true;
                }
            }
        }
        return false;
    }

    private static void handshakeWithClient(BufferedReader in, PrintWriter out) throws IOException {
        System.out.println("Sending string: '" + WELCOME_MESSAGE);
        out.println(WELCOME_MESSAGE);
        String clientHostname = in.readLine();
        System.out.println("Received Client Hostname: " + clientHostname);
        String clientIPAddress = in.readLine();
        System.out.println("Received Client IPAddress: " + clientIPAddress);
    }

    public static void main(String args[]) throws IOException {

        String message;
        ServerSocket srvr = null;
        Socket skt = null;
        PrintWriter out = null;

        try {
            //Detecting the localhost's ip address
            InetAddress localaddr = InetAddress.getLocalHost();
            System.out.println("Local IP Address : " + localaddr);
            System.out.println("Local hostname : " + localaddr.getHostAddress());
            // Creating a server socket for connection
            srvr = new ServerSocket(1234);
            System.out.println("Waiting for connection on " + localaddr);
            // Accept incoming connection
            skt = srvr.accept();
            System.out.print("Server has connected!\n"); // get Input and Output streams
            out = new PrintWriter(skt.getOutputStream(), true);
            out.flush();
            BufferedReader in = new BufferedReader(new InputStreamReader(skt.getInputStream()));

            //sends welcome message
            handshakeWithClient(in, out);

            boolean authenticated = authenticateUser(in, out);

            if (authenticated == true) {
                do {
                    out.println("enter a message");
                    message = in.readLine();
                    System.out.println("client>" + message);


                } while (!message.equals("bye"));
            } else {
                System.out.println("Authentication Failed!");
            }

            out.println("server>Server closing");
            System.out.println("server>Server closing");


        } catch (BindException e) {
            e.printStackTrace();
            System.out.print("A server is already running on the same port.");
        } catch (SocketException e) {
            e.printStackTrace();
            System.out.print("Client has disconnected rudely.");
        } catch (Exception e) {
            e.printStackTrace();
            System.out.print(e);
        } finally {
            if (out != null) {
                out.close();
            }
            if (skt != null) {
                skt.close();
            }
            if (srvr != null) {
                srvr.close();
            }
        }
    }
}