Here is a working example in Perl. Read RFC 821 for the protocol. Unless you are familiar with socket.h and socket.c I would suggest using IO::Socket::INET as it is much more intuitive to use. Note Net::SMTP is a much better option than code like this simple example which is just to show how it works.
#!/usr/bin/perl -w
use strict;
use IO::Socket::INET;
# see RFC 821 http://www.ietf.org/rfc/rfc0821.txt
my $forged_from = 'hotmail.com';
my $from = 'nobody@hotmail.com';
my $to = 'smtp_test@hotmail.com';
my $msg = "Subject: Subject\n\nHello me!\n\nNew Line\nMore Lin
+es\n";
my $server = 'xxxx.xxxx.net.au'; # SMTP SERVER
my $port = 25;
my $timeout = 10;
my $sock = IO::Socket::INET->new( PeerAddr => $server,
PeerPort => $port,
Proto => 'tcp',
Timeout => $timeout,
);
unless ( $sock ) {
die"ERR - Could not connect socket to $server on port $port";
}
if ( my $server = <$sock>) {
print "Got Handshake: $server";
dialog( $sock, "HELO $forged_from\015\012" );
dialog( $sock, "MAIL FROM: $from\015\012" );
dialog( $sock, "RCPT TO: $to\015\012" );
dialog( $sock, "DATA\015\012" );
dialog( $sock, "$msg\015\012.\015\012" );
dialog( $sock, "QUIT\015\012" );
}
else {
die "No handshake sent from SMTP server\n"
}
sub dialog {
my ( $sock, $send ) = @_;
print $sock $send;
print "Sent: $send";
my $receive = <$sock>;
die "Got no response to $send" unless $receive;
print "Recv: $receive";
}
__DATA__
Got Handshake: 220 xxxx.xxxx.net.au ESMTP Sendmail 8.11.6/8.11.6; Sat,
+ 20 Dec 2003 21:39:21 +1100 (EST)
Sent: HELO hotmail.com
Recv: 250 xxxx.xxxx.net.au Hello blah.blah.blah.blah.com.au [203.220.x
+xx.xxx], pleased to meet you
Sent: MAIL FROM: nobody@hotmail.com
Recv: 250 2.1.0 nobody@hotmail.com... Sender ok
Sent: RCPT TO: smtp_test@hotmail.com
Recv: 250 2.1.5 smtp_test@hotmail.com... Recipient ok
Sent: DATA
Recv: 354 Please start mail input.
Sent: Subject: Subject
Hello me!
New Line
More Lines
.
Recv: 250 Mail queued for delivery.
Sent: QUIT
Recv: 221 Closing connection. Good bye.
