把十六進位轉十進位

最近在找PERL有關於進位的轉換，好像比較少

為什麼呢？
因為在PERL的世界裡，不用宣告這個變數是什麼特別格式

一時是整數，有時是字串…
但你要知道如果變數內的2B值如何變成十進位

也就是如果在螢幕上看到的是 A--->ASC II是65(這是十進位表示)---->或是十六進位表示是0x41

這次我是要把AAA當成十六進位的0x00414141轉為十進位的4276545

或許有人會問為什麼要這樣作，因為我目前遇到的問題是封包問題，因封包Packet分析的器Wireshark上某一欄位看到的是1B，我想轉成十進位來看裡面的東西

好比是IP位置，PORT號，轉成十進位比較好看

目的是把ASC II旳值轉成十進位看

#!/usr/bin/perl

use strict;
my $tt;
my $go1=chr(65); #大寫A的十進位為65
my $go2=chr(0x41); #大寫A的十六進位為41
my $go3=chr(0x41);

my $text="$go1$go2$go3"; #合起來當作是十六進位0AAA轉十進位來看

print "$text\n";
my $tot=0;
my $ligh=length($text);
for(my $i=0;$i < $ligh;$i++){
my $SC=substr($text,$i,1);

if(ord($SC)!=0 ){
$tt=int(ord($SC)/16)*(16**(($ligh*2)-($i*2)-1))+int(ord($SC)%16)*(16**(($ligh*2)-($i*2)-2));

#print " $i\t".ord($SC)."\t$SC\t";

print $tt,'+';

}
$tot=$tot+$tt;

}
print ' 轉成10進位後',"\t$tot\n";

最近買了一本好書

Network Programming with Perl

這一本不錯，有在台北天瓏找到中文版的

網路上也找到原文的電子書

下載
在於支持作者，我還是跑去買了一本

原文書要一千多，在天瓏的中文版，$680，就買了，厚度還是很厚

老闆說這本已經第九刷了

裡面除了解說IO::Socket以外，還說了物件的關係，<>角符號的使用、open()、sysopen()、read()、sysread()、以二進位方式開始檔案的binmode()……

還有很多網路protocol的使用方法
smtp,pop,ftp,imap,nntp,web,telnet……UDP程式設計、Broadcasting、Multicasting

還有用perl寫多執行緒應用程式……

很多很多，這本是一本很好的進階書

原文介紹：

Network Programming with Perl is a comprehensive, example-rich guide to creating network-based applications using the Perl programming language. Among its many capabilities, modern Perl provides a straightforward and powerful interface to TCP/IP, and this book shows you how to leverage these capabilities to create robust, maintainable, and efficient custom client/server applications.

The book quickly moves beyond the basics to focus on high-level, application programming concepts, tools, and techniques. Readers will find a review of basic networking concepts and Perl fundamentals, including Perl's I/O functions, process model, and object-oriented extensions. In addition, the book examines a collection of the best third-party modules in the Comprehensive Perl Archive Network, including existing network protocols for e-mail, news, and the Web.

The core of the book focuses on methods and alternatives for designing TCP-based client/server systems, and more advanced techniques for specialized applications. Some of the specific topics covered are: The Berkeley Sockets API; The TCP protocol and the IO::Socket API; FTP file-sharing service; The Net::Telnet module for adapting clients to interactive network services; SMTP, including how to create and send e-mails with multimedia attachments; HTTP and the LWP module for communicating with Web servers; Bulletproofing servers; Broadcasting and multicasting; and Interprocess communication with UNIX domain sockets.

Useful, working programs demonstrate ideas and techniques in action, including a real-time chat and messaging system, a program for processing e-mail containing MIME attachments, a program for mirroring an FTP site, and a Web robot.

Network Programming with Perl focuses on TCP/IP rather than just the common Web protocols. Modeled after the critically acclaimed TCP/IP Illustrated by W. Richard Stevens, this book achieves a level of detail far superior to most. It is an essential resource for network administrators and Perl programmers who are creating network applications.