hi everybody :)
recently i am learning about perl socket programming. i found a tutorial and sample about using perl to send email (through socket). i try to run that script but not successful. then i try to debug it but there are something that i dont understand. so i decide to ask you all :)

here is part of the sample code that i dont understand:

use Socket;
use strict;


my($mailTo)     = 'me@here';


my($mailServer) = 'host.there';


my($mailFrom)   = 'me@here';
my($realName)   = "Ralph Martin";
my($subject)    = 'Test';
my($body)       = "Test Line One.\nTest Line Two.\n";


$main::SIG{'INT'} = 'closeSocket';


my($proto)      = getprotobyname("tcp")        || 6;
my($port)       = getservbyname("SMTP", "tcp") || 25;
my($serverAddr) = (gethostbyname($mailServer))[4];


if (! defined($length)) {


    die('gethostbyname failed.');
}


socket(SMTP, AF_INET(), SOCK_STREAM(), $proto)
    or die("socket: $!");


$packFormat = 'S n a4 x8';   # Windows 95, SunOs 4.1+
#$packFormat = 'S n c4 x8';   # SunOs 5.4+ (Solaris 2)


connect(SMTP, pack($packFormat, AF_INET(), $port, $serverAddr))
    or die("connect: $!");
[download]

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i dont understand about $mailserver, $proto, $port, $serverAddr and $packFormat.

the explaination that i get from the web are as below, but i'm still abit confused.

-Initialize $mailServer which holds the symbolic name of your mail server.
-Get the protocol number for the tcp protocol and the port number for the smtp service. Recall: Windows 95 and NT do not implement the getprotobyname()or getservbyname() functions so default values are supplied.
-Initialize $serverAddr with the mail server's Internet address.
-Initialize $packedFormat with format specifiers.


my questions are:
1. is $mailserver means my computer name? or the hostname of the gateway of my LAN? or something like "smtp.streamyx.com"?
2. why do i need the tcp protocol? i want to send email, so i only need smtp, right?
3. is $serverAddr means the ip address of my pc? or the ip address of the gateway? or else?
4. what is $packedFormat means? it is for what?


that's all my questions. if u need more information about the scripts for sending email using socket, u can go to http://www.cs.cf.ac.uk/Dave/PERL/node180.html


ok, thank you very much :)


regards,
hweefarn

20031220 Edit by Corion: Changed formatted code to CODE tags

20031221 Edit by jeffa: Aliased email addresses