How To: Perl TCP / UDP Socket Programming using IO::Socket::INET

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　　http://www.thegeekstuff.com/2010/07/perl-tcp-udp-socket-programming/
　　In this article, let us discuss how to write Perl socket programming using the inbuilt socket modules in Perl.
　　Perl socket modules provides an object interface that makes it easier to create and use TCP / UPD sockets.
　　This article covers the following topics:

• Perl example code for TCP client and server
  
• Perl example code for UDP client and server
  
• Read and write descriptor list using Select(IO::Select)
  

　　
　　CPAN module IO::Socket::INET is used to perform socket operations such as — creating, binding, connecting, listening and closing the socket.
　　IO::Select module is used for obtaining the descriptors that are ready for read/write operations.

Perl TCP Client and Server
　　TCP is a connection oriented networking protocol. In this example, let us review the Perl code-snippet that will explaining us the simple client and server communication.

Perl TCP Server Operation
　　The socket operation such as socket creation, binding and listening to the socket is performed by the IO::Socket::INET module.
　　The Perl code given below does the following:

• Create the Socket
  
• Bind the socket to an address and port
  
• Listen to the socket at the port address
  
• Accept the client connections
  
• Perform read/write operation on the socket.
  

#!c:\perl\bin\perl.exe
#tcpserver.pl
use IO::Socket::INET;
# flush after every write
$| = 1;
my ($socket,$client_socket);
my ($peeraddress,$peerport);
# creating object interface of IO::Socket::INET modules which internally does
# socket creation, binding and listening at the specified port address.
$socket = new IO::Socket::INET (
LocalHost => '61.52.222.111',
LocalPort => '8888',
Proto => 'tcp',
Listen => 5,
Reuse => 1
) or die"ERROR in Socket Creation : $!\n";
print "SERVER Waiting for client connection on port 8888";
while(1)
{
# waiting for new client connection.
$client_socket = $socket->accept();
# get the host and port number of newly connected client.
$peer_address = $client_socket->peerhost();
$peer_port = $client_socket->peerport();
print "Accepted New Client Connection From : $peeraddress:$peerport\n";
# write operation on the newly accepted client.
$data = "DATA from Server";
print $client_socket "$data\n";
# we can also send the data through IO::Socket::INET module,
# $client_socket->send($data);
# read operation on the newly accepted client
$data = <$client_socket>;
# we can also read from socket through recv()  in IO::Socket::INET
# $client_socket->recv($data,1024);
print "Received from Client : $data\n";
}
$socket->close();
　　

Perl TCP Client Operation
　　The Perl code given below does the following:

• Create the socket.
  
• Connect to the remote machine at a specific port.
  
• Perform read/write operation on the socket.
  

#!c:\perl\bin\perl.exe
#tcpclient.pl
use IO::Socket::INET;
# flush after every write
$| = 1;
my ($socket,$client_socket);
# creating object interface of IO::Socket::INET modules which internally creates
# socket, binds and connects to the TCP server running on the specific port.
$socket = new IO::Socket::INET (
PeerHost => '61.52.222.111',
PeerPort => '8888',
Proto => 'tcp',
) or die "ERROR in Socket Creation : $!\n”;
print "TCP Connection Success.\n”;
# read the socket data sent by server.
$data = <$socket>;
# we can also read from socket through recv()  in IO::Socket::INET
# $socket->recv($data,1024);
print "Received from Server : $data\n”;
# write on the socket to server.
$data = "DATA from Client”;
print $socket "$data\n”;
# we can also send the data through IO::Socket::INET module,
# $socket->send($data);
sleep (10);
$socket->close();
　　

Perl UDP Server
　　The Perl code given below does the following:

• Create the socket.
  
• Bind the socket to the specific port.
  

#!c:\perl\bin\perl.exe
#udpserver.pl
use IO::Socket::INET;
# flush after every write
$| = 1;
my ($socket,$received_data);
my ($peeraddress,$peerport);
#  we call IO::Socket::INET->new() to create the UDP Socket and bound
# to specific port number mentioned in LocalPort and there is no need to provide
# LocalAddr explicitly as in TCPServer.
$socket = new IO::Socket::INET (
LocalPort => '8888',
Proto => 'udp',
) or die "ERROR in Socket Creation : $!\n";
while(1)
{
# read operation on the socket
$socket->recv($recieved_data,1024);
#get the peerhost and peerport at which the recent data received.
$peer_address = $socket->peerhost();
$peer_port = $socket->peerport();
print "\n($peer_address , $peer_port) said : $recieved_data";
#send the data to the client at which the read/write operations done recently.
$data = "data from server\n";
print $socket "$data";
}
$socket->close();
Perl UDP Client
　　The Perl code given below does the following:

• Create the UDP client.
  
• Connect to the specific UDP server.
  
• Perform write and read operation on the socket.
  

#!c:\perl\bin\perl.exe
#udpclient.pl
use IO::Socket::INET;
# flush after every write
$| = 1;
my ($socket,$data);
#  We call IO::Socket::INET->new() to create the UDP Socket
# and bind with the PeerAddr.
$socket = new IO::Socket::INET (
PeerAddr   => '61.52.222.111:8888',
Proto        => 'udp'
) or die "ERROR in Socket Creation : $!\n";
#send operation
$data = "data from client";
$socket->send($data);
#read operation
$data = <$socket>;
print "Data received from socket : $data\n ";
sleep(10);
$socket->close();
　　
　　
　　http://www.tutorialspoint.com/perl/perl_socket_programming.htm
　　
　　To explain above mentioned socket concept we will take an example of Client - Server Programming using Perl.
　　To complete a client server architecture we would have to go through the following steps:

To create a server

• 　　Create a socket using socket call.
  
  
• 　　Bind the socket to a port address using bind call.
  
  
• 　　Listen to the socket at the port address using listen call.
  
  
• 　　Accept client connections using accept call.
  
  

To create a client

• 　　Create a socket with socket call.
  
  
• 　　Connect (the socket) to the server using connect call.
  
  

　　Following diagram shows complete sequence of the calls used by Client and Server to communicate with each other: