jlookup.java

本代码是用java编写的,用来查找目的主机开放端口信息的源码.

import java.net.*;
import java.io.*;
public class JLookup{
	public static void main(String args[])
	{ if(args.length>0)
	  { for(int i=0;i<=args.length;i++)
	     {lookup(args[0]);
	      System.out.println("");
	      }
	   }
	   else{System.out.println("Enter a hostname or IP.(\"Q\" to Quit)");
	        BufferedReader input=new BufferedReader(new InputStreamReader(System.in));
	        while(true)
	           {try{
				   String prompt="JLookUp>";
				   System.out.println(prompt);
				   String line=input.readLine().trim();
				   if(line.equalsIgnoreCase("Q"))
				      {input.close(); break;}
			        lookup(line);
			      }
			      catch(IOException ioe){ioe.printStackTrace();}
			    }
		    }
    }
  private static void lookup(String host)
  { InetAddress hostInetAddr[];
    try{hostInetAddr=InetAddress.getAllByName(host);
	   }
	   catch(UnknownHostException e)
	   {System.out.println("Unknown Host:"+host);
	    return;}
	if(isHostname(host))
	  {for(int i=0;i<hostInetAddr.length;i++)
	    {System.out.println(hostInetAddr[i].getHostAddress());}
      }
      else
      { for(int i=0;i<hostInetAddr.length;i++)
        {System.out.println(hostInetAddr[i].getHostName());}
	  }
    }
 private static boolean isHostname(String host)
  { char[] chHost=host.trim().toCharArray();
    for(int i=0;i<chHost.length;i++)
    {if(chHost[i]!='.'&&(chHost[i]<'0'||chHost[i]>'9'))
       { return true;
		}
    }
    return false;
  }
}