1,ip地址和主机名互换
package getip;
import java.net.InetAddress;
import java.net.UnknownHostException;
public class GetIP {
public static void main(String[] args) {
InetAddress addr= null;
if(args.length==0){
System.out.println("usage:java GetIP hostname");
System.exit(1);
}
try {
addr = InetAddress.getByName(args[0]);
} catch (UnknownHostException e) {
System.out.println("I can't find"+args[0]);
System.exit(2);
}
// byte[] add = addr.getAddress(); //返回字节数组
// for(byte i:add){
// System.out.println(i);
// }
// getHostName()返回主机名,getHostAddress()返回地址
System.out.println(addr.getHostName()+"="+addr.getHostAddress());
try {
InetAddress[] allAddrs = InetAddress.getAllByName(args[0]);//一台主机可能对应多个ip
for(InetAddress a:allAddrs){
System.out.println(a); //InetAddress.toString的隐含调用,自动输出 "主机名/ip地址"
}
} catch (UnknownHostException e) {
e.printStackTrace();
}
}
}
如果执行参数主机名为www.sina.com,结果如下
www.sina.com=121.194.0.206
www.sina.com/121.194.0.206
www.sina.com/121.194.0.207
www.sina.com/121.194.0.208
www.sina.com/121.194.0.209
www.sina.com/121.194.0.210
www.sina.com/121.194.0.203
www.sina.com/121.194.0.205
2,测试连接某个服务,如web服务器
package testConn;
import java.io.IOException;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;
//测试连接web服务器
public class WebPing {
public static void main(String[] args) {
try {
InetAddress addr= null;
Socket socket = new Socket(args[0],80);//80端口是web服务
addr=socket.getInetAddress();
System.out.println("connected to "+addr);
socket.close();
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
System.out.println("can't connect to "+args[0]);
}
}
}
参数为www.sina.com结果
connected to www.sina.com/121.194.0.206
如果端口被占用出现,如参数为localhost时
can't connect to localhost
3,扫描出计算机正在使用的端口号
package usedport;
import java.io.IOException;
import java.net.ServerSocket;
//扫描出计算机中正在使用的端口,使用ServerSocket构造函数是否有异常判断
public class LocalScan {
public static void main(String[] args) {
for (int i = 0; i < 1023; i++) {
testPort(i);
}
System.out.println("completed! ");
}
private static void testPort(int i) {
try {
ServerSocket server = new ServerSocket(i);
} catch (IOException e) {
System.out.println("Port " + i + " in use!");
}
}
}
结果:
Port 135 in use!
Port 445 in use!
。。。
。。。
completed!