How is it work the event handlers!? Post: 302980805

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Top Forums Programming How is it work the event handlers!? Post 302980805 by flaviofachin on Friday 2nd of September 2016 08:11:07 AM

09-02-2016

Registered User

How is it work the event handlers!?

I just have started studying perl and I can not figure out what is the exact strategy used in the following script to handle events.

Precisely, what I do not understand is if the loop that is in charge to control the state of the socket, is managed at the system level (where the process will be locked inside the scheduler and so the following code must be read sequentially) or if this happens anywhere else, or maybe just in these "while loop" that apparently are based on the success of the setting of a variable.

Especially the "while" block at the server-side leaves me some concern.

Script to Create a Server

Code:

#!/usr/bin/perl -w
# Filename : server.pl

use strict;
use Socket;

# use port 7890 as default
my $port = shift || 7890;
my $proto = getprotobyname('tcp');
my $server = "localhost";  # Host IP running the server

# create a socket, make it reusable
socket(SOCKET, PF_INET, SOCK_STREAM, $proto)
   or die "Can't open socket $!\n";
setsockopt(SOCKET, SOL_SOCKET, SO_REUSEADDR, 1)
   or die "Can't set socket option to SO_REUSEADDR $!\n";

# bind to a port, then listen
bind( SOCKET, pack_sockaddr_in($port, inet_aton($server)))
   or die "Can't bind to port $port! \n";

listen(SOCKET, 5) or die "listen: $!";
print "SERVER started on port $port\n";

# accepting a connection
my $client_addr;
while ($client_addr = accept(NEW_SOCKET, SOCKET)) {
   # send them a message, close connection
   my $name = gethostbyaddr($client_addr, AF_INET );
   print NEW_SOCKET "Smile from the server";
   print "Connection recieved from $name\n";
   close NEW_SOCKET;
}
To run the server in background mode issue the following command on Unix prompt −

$perl sever.pl&
Script to Create a Client

Code:

#!/usr/bin/perl -w
# Filename : client.pl

use strict;
use Socket;

# initialize host and port
my $host = shift || 'localhost';
my $port = shift || 7890;
my $server = "localhost";  # Host IP running the server

# create the socket, connect to the port
socket(SOCKET,PF_INET,SOCK_STREAM,(getprotobyname('tcp'))[2])
   or die "Can't create a socket $!\n";
connect( SOCKET, pack_sockaddr_in($port, inet_aton($server)))
   or die "Can't connect to port $port! \n";

my $line;
while ($line = <SOCKET>) {
        print "$line\n";
}
close SOCKET or die "close: $!";

Thanks for any answare!

flaviofachin

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LEARN ABOUT DEBIAN

net-server

NET-SERVER(1p)						User Contributed Perl Documentation					    NET-SERVER(1p)

NAME

       net-server - Base Net::Server starting module

SYNOPSIS

	   net-server [base type] [net server arguments]

	   net-server PreFork ipv '*'

	   net-server HTTP

	   net-server HTTP app foo.cgi

	   net-server HTTP app foo.cgi app /=bar.cgi

	   net-server HTTP port 8080 port 8443/ssl ipv '*' server_type PreFork --SSL_key_file=my.key --SSL_cert_file=my.crt access_log_file STDERR

DESCRIPTION

       The net-server program gives a simple way to test out code and try port connection parameters.  Though the running server can be robust
       enough for full tim use, it is anticipated that this binary will just be used for basic testing of net-server ports, acting as a simple
       echo server, or for running development scripts as CGI.

OPTIONS

       "base type"
	   The very first argument may be a Net::Server flavor.  This is given as shorthand for writing out server_type "ServerFlavor".
	   Additionally, this allows types such as HTTP and PSGI, which are not true Net::Server base types, to subclass other server types via an
	   additional server_type argument.

	       net-server PreFork

	       net-server HTTP	# becomes a HTTP server in the Fork flavor

	       net-server HTTP server_type PreFork  # preforking HTTP server

       "port"
	   Port to bind upon.  Default is 80 if running a HTTP server as root, 8080 if running a HTTP server as non-root, or 20203 otherwise.

	   Multiple value can be given for binding to multiple ports.  All of the methods for specifying port attributes enumerated in Net::Server
	   and Net::Server::Proto are available here.

	       net-server port 20201

	       net-server port 20202

	       net-server port 20203/IPv6

       "host"
	   Host to bind to.  Default is *.  Will bind to an IPv4 socket if an IPv4 address is given.  Will bind to an IPv6 socket if an IPv6
	   address is given (requires installation of IO::Socket::INET6).

	   If a hostname is given and "ipv" is still set to 4, an IPv4 socket will be created.	If a hostname is given and "ipv" is set to 6, an
	   IPv6 socket will be created.  If a hostname is given and "ipv" is set to * (default), a lookup will be performed and any available IPv4
	   or IPv6 addresses will be bound.  The "ipv" parameter can be set directly, or passed along in the port, or additionally can be passed
	   as part of the hostname.

	       net-server host localhost

	       net-server host localhost/IPv4

       There are many more options available.  Please see the Net::Server documentation.

AUTHOR

	   Paul Seamons <paul at seamons.com>

LICENSE

       This package may be distributed under the terms of either the

	 GNU General Public License
	   or the
	 Perl Artistic License

perl v5.14.2							    2012-06-12							    NET-SERVER(1p)