This is the thirteenth set of slides from a Perl programming course that I held some years ago. I want to share it with everyone looking for intransitive Perl-knowledge. A table of content for all presentations can be found at i-can.eu. The source code for the examples and the presentations in ODP format are on https://github.com/kberov/PerlProgrammingCourse

1. Perl Programming
Course
Network programming
Krassimir Berov
I-can.eu

2. Contents
1. Sockets, servers and clients
2. TCP/IP, UDP sockets
3. Unix Domain Socket (UDS) sockets
4. IO::Socket
5. HTTP and SMTP
6. LWP and WWW::Mechanize

3. Sockets, servers and clients
• Socket
• an end-point of a bi-directional communication link
in the Berkeley sockets API
• Berkeley sockets API allows communications
between hosts or between processes on one
computer
• One of the fundamental technologies underlying the
Internet.
• A network socket is a communication end-point
unique to a machine communicating on an Internet
Protocol-based network, such as the Internet.
• Unix domain socket, an end-point
in local inter-process communication

4. Sockets, servers and clients
• Server
• An application or device that performs
services for connected clients as part of a
client-server architecture
• An application program that accepts
connections in order to service requests by
sending back responses
• Example:
web servers(Apache), e-mail servers(Postfix),
file servers

5. Sockets, servers and clients
• Client
• An application or system that accesses a
(remote) service on another computer
system known as a server
• Example:
Web browsers (Internet Explorer, Opera,
Firefox)
Mail Clients (Thunderbird, KMail, MS
Outlook)

6. TCP/IP, UDP sockets
• An Internet socket is composed of
• Protocol (TCP, UDP, raw IP)
• Local IP address
• Local port
• Remote IP address
• Remote port

7. Unix Domain Socket
• A Unix domain socket (UDS)
or IPC socket
• inter-process communication socket
• a virtual socket
• similar to an internet socket
• used in POSIX operating systems for inter-
process communication
• connections appear as byte streams, much like
network connections,
• all data remains within the local computer

8. IO::Socket
• IO::Socket - Object interface to socket
communications
• built upon the IO::Handle interface and inherits
all its methods
• only defines methods for operations common to
all types of socket
• Operations, specified to a socket in a particular
domain have methods defined in sub classes
• will export all functions (and constants) defined
by Socket

9. IO::Socket
• IO::Socket – Example (TCP/IP)
#io-socket-tcp-client.pl
use IO::Socket;
my $sock = IO::Socket::INET->new(
PeerAddr => $host,
PeerPort => "$port",
Proto => 'tcp',
Timeout => 60
) or die $@;
die "Could not connect to $host$/"
unless $sock->connected;
#...

10. IO::Socket
• IO::Socket – Example 2 (TCP/IP)
#io-socket-tcp-server.pl
use IO::Socket;
my ($host, $port, $path ) = ( 'localhost', 8088 );
my $server = new IO::Socket::INET (
LocalAddr => $host,
LocalPort => $port,
Proto => 'tcp',
Listen => 10,
Type => SOCK_STREAM,
ReuseAddr => 1
);
print "Server ($0) running on port $port...n";
while (my $connection = $server->accept) {
#...

11. IO::Socket
• IO::Socket – Example (UDS)
#io-socket-uds-server.pl
use IO::Socket;
my $file = "./udssock";
unlink $file;
my $server = IO::Socket::UNIX->new(
Local => $file,
Type => SOCK_STREAM,
Listen => 5
) or die $@;
print "Server running on file $file...n";
#...

12. IO::Socket
• IO::Socket – Example 2 (UDS)
#io-socket-uds-client.pl
use IO::Socket;
my $server = IO::Socket::UNIX->new(
Peer => "./udssock",
) or die $@;
# communicate with the server
print "Client connected.n";
print "Server says: ", $server->getline;
$server->print("Hello from the client!n");
$server->print("And goodbye!n");
$server->close;
#...

13. IO::Socket
• IO::Socket – Example (UDP)
#io-socket-udp-server.pl
use IO::Socket;
my $port = 4444;
my $server = new IO::Socket::INET(
LocalPort => $port,
Proto => 'udp',
);
die "Bind failed: $!n" unless $server;
print "Server running on port $port...n";
#...

14. IO::Socket
• IO::Socket – Example 2 (UDP)
#io-socket-udp-client.pl
use IO::Socket;
my $host = 'localhost';
my $port = 4444;
my $client = new IO::Socket::INET(
PeerAddr => $host,
PeerPort => $port,
Timeout => 2,
Proto => 'udp',
);
$client->send("Hello from client") or die "Send: $!n";
my $message;
$client->recv($message, 1024, 0);
print "Response was: $messagen";
#...

15. HTTP and SMTP
• HTTP
• SMTP

16. Sending Mail
• Net::SMTP
#smtp.pl
use Net::SMTP;
my $smtp = Net::SMTP->new(
Host => 'localhost',
Timeout => 30,
Hello =>'localhost',
);
my $from = 'me@example.com';
my @to = ('you@example.org',);
my $text = $ARGV[0]|| 'проба';
my $mess = "ERROR: Can't send mail using Net::SMTP. ";
$smtp->mail( $from ) || die $mess;
$smtp->to( @to, { SkipBad => 1 } ) || die $mess;
$smtp->data( $text ) || die $mess;
$smtp->dataend() || die $mess;
$smtp->quit();

17. LWP and WWW::Mechanize
• LWP - The World-Wide Web library for Perl
• provides a simple and consistent application
programming interface (API)
to the World-Wide Web
• classes and functions that allow you to write
WWW clients
• also contains modules that help you implement
simple HTTP servers
• supports access to http, https, gopher, ftp, news,
file, and mailto resources
• transparent redirect, parser for robots.txt files
etc...

18. LWP and WWW::Mechanize
• WWW::Mechanize - Handy web browsing in a
Perl object
• helps you automate interaction with a website
• well suited for use in testing web applications
• is a proper subclass of LWP::UserAgent
• you can also use any of the LWP::UserAgent's
methods.

19. LWP and WWW::Mechanize
• WWW::Mechanize - Example
• helps you automate interaction with a website
• well suited for use in testing web applications
• is a proper subclass of LWP::UserAgent
• you can also use any of the LWP::UserAgent's
methods.

20. LWP and WWW::Mechanize
• Example – getting product data from a site
#www_mech.pl
use strict; use warnings;
use MyMech;
use Data::Dumper;
#Config
$MyMech::Config->{DEBUG}=0;
my $Config = $MyMech::Config;
#print Dumper($Config);
my $mech = MyMech->new(
agent => $Config->{agent},
cookie_jar => $Config->{cookie_jar},
autocheck => $Config->{autocheck},
onwarn => $Config->{onwarn}
);
#...

21. Network programming
• Resources
• Beginning Perl
(Chapter 14 – The World of Perl/IPC and
Networking)
• Professional Perl Programming
(Chapter 23 – Networking with Perl)
• perldoc perlipc
• perldoc IO::Socket
• http://en.wikipedia.org/wiki/Berkeley_sockets
• Perl & LWP (http://lwp.interglacial.com/)

22. Network programming
Questions?