Socket.pm - The Socket Module

Perl Tutorials - Herong's Tutorial Examples

Dr. Herong Yang, Version 5.10

Perl Tutorials - Herong's Tutorial Examples

∟Socket.pm - The Socket Module

This section provides a tutorial example on how to use the Socket.pm module to creating sockets and establish network communication connections.

In the previous examples, there are a lots hard coded values, like socket domain and socket type. The Socket Module is designed to help you to hide those values. It also offers a number of methods to pack and unpack IP addresses and socket addresses.

PF_INET - Returns the socket domain number of Internet domain.

SOCK_STREAM - Returns the socket type number for sequenced, reliable, two-way connection, byte streams

INADDR_ANY - Returns the packed wildcard IP address, similar to pack('C4', 0,0,0,0).

inet_aton("216.109.118.67") - Returns the packed form of the specified IP address, similar to pack('C4', 216,109,118,67). inet_aton("www.yahoo.com") works too.

inet_aton($pHost) - Returns the unpacked form of the specified packed IP address.

pack_sockaddr_in($port, $pHost) - Returns the packed socket address of the specified port number and packed IP address. Internet domain number will be automatically added. This function is similar to pack('S n a4 x8', $domain, $port, $pHost);

unpack_sockaddr_in($address) - Returns port name and packed IP address in an array of the specified packed socket address.

sockaddr_in($port, $pHost) - Same as pack_sockaddr_in($port, $pHost) in scalar context.

sockaddr_in($address) - Same as unpack_sockaddr_in($address) in list context.

I revised the Reverse Echoer server application with the help of Socket Module:

#- ReverseEchoer2.pl
#- Copyright (c) 1999 by Dr. Herong Yang, http://www.herongyang.com/
#
   use Socket;
   $proto = getprotobyname('tcp');
   socket(SOCK,PF_INET,SOCK_STREAM,$proto);
   $host = INADDR_ANY;
   $port = 8888;
   $address = pack_sockaddr_in($port, $host);
   bind(SOCK, $address);
   $queueSize = 5; # Queue up to 5 connections
   listen(SOCK, $queueSize);
   $hostName = inet_ntoa($host);
   print STDOUT "Server host: $hostName\n";
   print STDOUT "Server port: $port\n";
   $cAddress = accept(NEWSOCK,SOCK);
   ($cPort, $cHost) = unpack_sockaddr_in($cAddress);
   $cHostName = inet_ntoa($cHost);
   print STDOUT "Client host: $cHostName\n";
   print STDOUT "Client port: $cPort\n";
   select(NEWSOCK); $| = 1; select(STDOUT);
   print NEWSOCK "Welcome to Reverse Echo Server.\r\n";
   while ($m=<NEWSOCK>) {
      $m =~ s/\n|\r//g;
      last if ($m eq ".");
      $m = reverse($m);
      print NEWSOCK "$m\r\n";
   }
   close(NEWSOCK);
   exit;

Table of Contents

About This Book

Perl on Linux Systems

ActivePerl on Windows Systems

Data Types: Values and Variables

Expressions, Operations and Simple Statements

User Defined Subroutines

Perl Built-in Debugger

Name Spaces and Perl Module Files

Symbolic (or Soft) References

Hard References - Addresses of Memory Objects

Objects (or References) and Classes (or Packages)