Java实现Internet地址获取

Java实现Internet地址获取

代码内容

• 输入域名输出IPV4地址
• 输入IP地址输出域名
• 支持命令行输入
• 支持交互式输入

代码实现

/* nslookup.java */
import java.net.*;
import java.util.regex.Pattern;
import java.io.*;

public class nslookup {
    public static void main(String[] args) {
        if (args.length > 0) {
            for (int i = 0; i < args.length; i++) {
                System.out.println("\n> " + args[i]);
                lookup(args[i]);
            }
        } else {
            BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
            System.out.println("Enter the domain names or IP addresses. Enter \"exit\" to quit.");
            try {
                boolean isEmptyLine = false;
                while (true) {
                    if (isEmptyLine){
                        isEmptyLine = false;
                        System.out.print("> ");
                    } else
                        System.out.print("\n> ");
                    String host = in.readLine();
                    if (host.equalsIgnoreCase("exit")) {
                        break;
                    } else if (host.isEmpty()){
                        isEmptyLine = true;
                        continue;
                    }
                    lookup(host);
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    private static void lookup(String host) {
        if(isDomain(host)) {
            nat(host, true);
        } else {
            nat(host, false);
        }
    }

    private static boolean isDomain(String host) {
        String[] part = host.split("\\.");
        if (part.length == 4) {
            for (String pa : part) {
                if (!isNumeric(pa)) {
                    return true;
                }
            }
            return false;
        } else {
            return true;
        }
    }

    public static boolean isNumeric(String str) {
        Pattern pattern = Pattern.compile("[0-9]*");
        //Pattern pattern = Pattern.compile("^[0-9]+(.[0-9]*)?$");
        return pattern.matcher(str).matches();
    }

    private static void nat(String host, boolean isDomain) {
        try {
            if (host.equals("127.0.0.1")){
                System.out.println("Name: localhost");
                return;
            }
            InetAddress[] address = InetAddress.getAllByName(host);
            if (isDomain) {
                for (int i = 0; i < address.length; i++){
                    System.out.println("Address: " + address[i].getHostAddress());
                }
            }
            else if (host.equals(address[0].getHostName())){
                for (int i = 0; i < address.length; i++){
                    System.out.println("Address: " + address[i].getHostAddress());
                }
            }
            else {
                for (int i = 0; i < address.length; i++){
                    System.out.println("Name: " + address[i].getHostName());
                }
            }
        } catch (UnknownHostException e) {
            e.printStackTrace();
        }
    }
}

运行截图

• 输入域名的结果
  

• 输入IP地址的结果
  

• 输入本机上IP地址的结果
  

增强版内容

• 在源程序的基础之上在输入域名时输出全部地址
• 如果查询的域名或者IP在本主机上还要输出对应的端口号
• 如果不在本主机上也需要给相应的提示信息

增强版代码实现

/* nslookupAdvanced.java */
import java.net.*;
import java.util.regex.Pattern;
import java.io.*;

public class nslookupAdvanced {
    public static void main(String[] args) {
        if (args.length > 0) {
            for (int i = 0; i < args.length; i++) {
                System.out.println("\n> " + args[i]);
                lookup(args[i]);
            }
        } else {
            BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
            System.out.println("Enter the domain names or IP addresses. Enter \"exit\" to quit.");
            try {
                boolean isEmptyLine = false;
                while (true) {
                    if (isEmptyLine){
                        isEmptyLine = false;
                        System.out.print("> ");
                    } else
                        System.out.print("\n> ");
                    String host = in.readLine();
                    if (host.equalsIgnoreCase("exit")) {
                        break;
                    } else if (host.isEmpty()){
                        isEmptyLine = true;
                        continue;
                    }
                    lookup(host);
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    private static void lookup(String host) {
        if(isDomain(host)) {
            nat(host, true);
            decideNI(host);
        } else {
            nat(host, false);
            decideNI(host);
        }
    }

    private static boolean isDomain(String host) {
        String[] part = host.split("\\.");
        if (part.length == 4) {
            for (String pa : part) {
                if (!isNumeric(pa)) {
                    return true;
                }
            }
            return false;
        } else {
            return true;
        }
    }

    public static boolean isNumeric(String str) {
        Pattern pattern = Pattern.compile("[0-9]*");
        //Pattern pattern = Pattern.compile("^[0-9]+(.[0-9]*)?$");
        return pattern.matcher(str).matches();
    }

    private static void nat(String host, boolean isDomain) {
        try {
            if (host.equals("127.0.0.1")){
                System.out.println("Name: localhost");
                return;
            }
            InetAddress[] address = InetAddress.getAllByName(host);
            if (isDomain || host.equals(address[0].getHostName())) {
                for (int i = 0; i < address.length; i++) {
                    System.out.println("Address: " + address[i].getHostAddress());
                }
            } else {
                System.out.println("Name: " + address[0].getHostName());
            }
        } catch (UnknownHostException e) {
            e.printStackTrace();
        }
    }

    private static void decideNI(String host) {
        try {
            InetAddress address = InetAddress.getByName(host);
            NetworkInterface ni = NetworkInterface.getByInetAddress(address);
            if (ni != null) {
                String niName = ni.getName();
                String[] niDisplayName = ni.getDisplayName().split(" ");
                System.out.println("This is local address " + niName + 
                    niDisplayName[niDisplayName.length - 1] + ".");
            } else {
                System.out.println("This is not local address.");
            }
        } catch (SocketException e) {
            e.printStackTrace();
        } catch (UnknownHostException e) {
            e.printStackTrace();
        }
    }
}

增强版运行结果

• 输入一个绑定到多个IP地址上的域名的结果
  

• 输入IP地址的结果