Into the Future.....

"At every cross road on the path that leads to the future, tradition has placed 10,000 men to guard the past."

- Maurice Maeterlinck

Attitude......

“The longer I live, the more I realize the impact of attitude on life. Attitude, to me, is more important than facts. It is more important than the past, the education, the money, than circumstances, than failure, than successes, than what other people think or say or do. It is more important than appearance, giftedness or skill. It will make or break a company... a church... a home. The remarkable thing is we have a choice everyday regarding the attitude we will embrace for that day. We cannot change our past... we cannot change the fact that people will act in a certain way. We cannot change the inevitable. The only thing we can do is play on the one string we have, and that is our attitude. I am convinced that life is 10% what happens to me and 90% of how I react to it. And so it is with you... we are in charge of our Attitudes.”

~ Charles R. Swindoll

Starting ZoneMinder: Can't open config file '/usr/local/etc/zm.conf': No such file or directory at /usr/local/share/perl/5.10.0/ZoneMinder/Config.pm

This error had wasted half a day of mine............. But ultimately i came to know that its a silly installation issue, which is related to previous installations of zoneminder !

Just go to "/usr/local/share/perl/5.10.0/" and remove Zoneminder folder manually from there... Thatz it !

Now you can reinstall the debian package & hope it works !

Interesting Web Collections !

Royalty free geographical photographs:

http://windowsonourworld.com/

Dan Pollock's Site of the day:

http://someonewhocares.org/siteoftheday/

Reference Site of the day :

http://www.refdesk.com/

Online Icon Maker:

http://www.rw-designer.com/online_icon_maker.php

Free online GPL podcast receiver:

http://juicereceiver.sourceforge.net/

S/W to organizes your frequently used text phrases & paste them into any application:

http://www.phraseexpress.com/

Create you own website for free:

http://www.weebly.com/

Free online file converter:

http://www.zamzar.com/

Textorizer:

http://textorizer.whatfettle.com/

Online image resizer:

http://mypictr.com/

External website monitoring service:

http://www.mon.itor.us/

Check all your email-box from one central place:

http://www.jump2mail.com

Create a free unique photo collage:

http://bighugelabs.com/hockney.php

Free receive only email (For times when you have to receive an email but you really don't want to give one that you actually use. ):

http://www.dodgeit.com/

Free Auto Bibliography Generator:

http://www.ottobib.com/

Really simple ways to share files:

http://www.zapr.com/

561 newspaper front pages from 57 countries:

http://www.newseum.org/

Great place to discover some of the up coming websites:

http://movers20.esnips.com/

Web designers search engine:

http://sparkl.us/

Online Photo Editors:

http://www.phixr.com/

http://www.flauntr.com/

Daytipper: daily tips, tricks and techniques:

http://www.daytipper.com

Picupine : Share photos for a week :

http://www.picupine.com/

Online rich media presentation tool:

http://www.empressr.com/

Google SketchUp to create, modify and share 3D models:

http://sketchup.google.com/

Online foreign language-learning site:

http://www.mangolanguages.com/

File search to search files in various file sharing and uploading sites:

http://www.filestube.com/

One Good Tech Blog:

http://www.labnol.org/

A free, complete, up-to-date, and reliable worldwide travel guide

http://wikitravel.org/

Free email tracking system that lets you know when the email you sent has been read by recipient:

http://www.spypig.com/

How to do just about everything:

http://www.ehow.com/

Free ebooks:

http://www.gutenberg.org/wiki/Main_Page

To find copies of your content on the Web:

http://www.copyscape.com/

Free uncompress service online:

http://www.wobzip.org/

Write in your own language online:

http://www.quillpad.com/

Encyclopedia:

http://www.eol.org/

Solving the issue of browser not opening php file (Ubuntu)

Just try the following.....

sudo /etc/init.d/apache2 stop
sudo apt-get remove --purge apache2 php5
sudo apt-get remove --purge libapache2-mod-php5
sudo apt-get install php5 apache2 libapache2-mod-php5
sudo /etc/init.d/apache2 start

Setting up of ACTi ACM 8511P camera in Zoneminder

ACTi Camera Setup 
************************
(You can setup the camera remotely through IP - Just connect as suggested in ACTi manual)
Streaming Method : RTP Over UDP
RTSP Authen Enable:  (BLANK)
RTP B2 Frame Enable: (BLANK)
Resolution : 640x480 (Used by my test setup - You can change it)
Frame Rate Mode : Constant
Frame Rate : 12 (Used by my test setup - You can change it)
Encoder Type : MPEG4
Video Bitrate Mode : Constant Bit Rate
Video Maximum Bitrate : Unlimited
Bitrate : 1.2M (Used by my test setup - You can change it)
RTSP Port : 7070
Video Control Port : 6001

Once you are done with the ACTi camera setup now you can open the zoneminder
for streaming the live video to your system.

Just install the zoneminder as detailed below on an Ubuntu PC:
Part - 1
*********
> ACTi work only on Zoneminder 1.24 So we need to use the source files provided
> in the zoneminder website rather then Ubuntu installation

Part - 2
*********
> Download DEB file from
> ftp://ftp.northern-ridge.com.au/zoneminder/1.24/debian/sid/zoneminder_1.24.2-1_i386.deb
> Install it on a Ubuntu PC

Part - 3
*********

ZoneMinder is now in the Debian repositories. There are downloadable .deb
files for Ubuntu for Edgy and Feisty. At this point it is in the
repository for Gutsy. After you install, you will need to do some
additional work, which is documented in the readme file included in the
package.
After installation do the following:
Link Apache
> sudo ln -s /etc/zm/apache.conf /etc/apache2/conf.d/zoneminder.conf
Restart Apache
> sudo /etc/init.d/apache2 restart

suid zmfix
> sudo chmod 4755 /usr/bin/zmfix

Run zmfix
> zmfix -a

Fix export problem
> sudo chown www-data.www-data /usr/share/zoneminder/temp

edit /etc/sysctl.conf and add the following lines (for 128meg shared mem)(**Maybe of use later**)
> kernel.shmall = 134217728
> kernel.shmmax = 134217728

Download cambozola.jar and put it in /usr/share/zoneminder (**Maybe of use later**)

> You should now be able to access the Zone Minder console through the web
> browser http://localhost/zm

For cambozola i think ***
> Enable in options->Images.
> Set path to ffmpeg in options -> Images /usr/bin/ffmpeg
> test with xawtv (-nodga may be needed)

Once the installation setup is done, open zoneminder in your browser and click on
"Add new monitor" and update the settings as shown below:


Zoneminder Setup
**********************
> General
Source Type: Remote
Function: Monitor
Maximim FPS: 12 (Used by my test setup - You can change it)
Alarm Maximum FPS: 30(Used by my test setup - You can change it)
Reference Image Blend : 7 (Used by my test setup - You can change it)

> Source
Remote Protocol: RTSP
Remote Method: RTP Unicast
Remote Hostname: 192.168.0.101 (Used by my test setup - You can change it)
Remote host port: 7070
Host path: live.sdp
Capture Width: 640  (Used by my test setup - You can change it)
Capture height: 480  (Used by my test setup - You can change it)
Orientation: Normal

Once you are done with the settings just save it and open your new monitor which you have added..... Thatz it.. You shall get the stream video on your remote PC.


For performing the PTZ setup on ACTi, i feel till now there is no direct method provided by the company.... but you can try the following method as a work around for the time being.

Goto "/usr/share/perl/5.10.0/ZoneMinder/Control" on your Ubuntu PC and do a back up of "AxisV2.pm" file.

Once its done just open the file using "sudo gedit AxisV2.pm" and replace the content with the following...

# ==========================================================================
#
# ZoneMinder Axis version 2 API Control Protocol Module, $Date: 2008-07-25 10:48:16 +0100 (Fri, 25 Jul 2008) $, $Revision: 2612 $
# Copyright (C) 2001-2008 Philip Coombes
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 2
# of the License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
#
# ==========================================================================
#
# This module contains the implementation of the Axis V2 API camera control
# protocol
#
package ZoneMinder::Control::AxisV2;

use 5.006;
use strict;
use warnings;

require ZoneMinder::Base;
require ZoneMinder::Control;

our @ISA = qw(ZoneMinder::Control);

our $VERSION = $ZoneMinder::Base::VERSION;

# ==========================================================================
#
# ACTi Control Protocol
#
# ==========================================================================

use ZoneMinder::Debug qw(:all);
use ZoneMinder::Config qw(:all);

use Time::HiRes qw( usleep );

sub new
{
my $class = shift;
my $id = shift;
my $self = ZoneMinder::Control->new( $id );
bless( $self, $class );
srand( time() );
return $self;
}

our $AUTOLOAD;

sub AUTOLOAD
{
my $self = shift;
my $class = ref($self) || croak( "$self not object" );
my $name = $AUTOLOAD;
$name =~ s/.*://;
if ( exists($self->{$name}) )
{
return( $self->{$name} );
}
Fatal( "Can't access $name member of object of class $class" );
}

sub open
{
my $self = shift;

$self->loadMonitor();

use LWP::UserAgent;
$self->{ua} = LWP::UserAgent->new;
$self->{ua}->agent( "ZoneMinder Control Agent/".ZM_VERSION );

$self->{state} = 'open';
}

sub close
{
my $self = shift;
$self->{state} = 'closed';
}

sub printMsg
{
my $self = shift;
my $msg = shift;
my $msg_len = length($msg);

Debug( $msg."[".$msg_len."]" );
}

sub sendCmd
{
my $self = shift;
my $cmd = shift;

my $result = undef;

printMsg( $cmd, "Tx" );

#print( "http://$address/$cmd\n" );
my $req = HTTP::Request->new( GET=>"http://".$self->{Monitor}->{ControlAddress}."$cmd" );
my $res = $self->{ua}->request($req);

if ( $res->is_success )
{
$result = !undef;
}
else
{
Error( "Error check failed: '".$res->status_line()."'" );
}

return( $result );
}

sub cameraReset
{
my $self = shift;
Debug( "Camera Reset" );
my $cmd = "/axis-cgi/admin/restart.cgi";
$self->sendCmd( $cmd );
}

sub moveConUp
{
my $self = shift;
Debug( "Move Up" );
my $cmd = "/cgi-bin/encoder?USER=admin&PWD=123456&MOVE=UP,3";
$self->sendCmd( $cmd );
}

sub moveConDown
{
my $self = shift;
Debug( "Move Down" );
my $cmd = "cgi-bin/encoder?USER=admin&PWD=123456&MOVE=DOWN,3";
$self->sendCmd( $cmd );
}

sub moveConLeft
{
my $self = shift;
Debug( "Move Left" );
my $cmd = "/cgi-bin/encoder?USER=admin&PWD=123456&MOVE=LEFT,3";
$self->sendCmd( $cmd );
}

sub moveConRight
{
my $self = shift;
Debug( "Move Right" );
my $cmd = "/cgi-bin/encoder?USER=admin&PWD=123456&MOVE=RIGHT,3";
$self->sendCmd( $cmd );
}

sub moveConUpRight
{
my $self = shift;
Debug( "Move Up/Right" );
my $cmd = "cgi-bin/encoder?USER=admin&PWD=123456&MOVE=UPRIGHT,3, 3";
$self->sendCmd( $cmd );
}

sub moveConUpLeft
{
my $self = shift;
Debug( "Move Up/Left" );
my $cmd = "cgi-bin/encoder?USER=admin&PWD=123456&MOVE=UPLEFT,3,3";
$self->sendCmd( $cmd );
}

sub moveConDownRight
{
my $self = shift;
Debug( "Move Down/Right" );
my $cmd = "cgi-bin/encoder?USER=admin&PWD=123456&MOVE=DOWNRIGHT,3,3";
$self->sendCmd( $cmd );
}

sub moveConDownLeft
{
my $self = shift;
Debug( "Move Down/Left" );
my $cmd = "cgi-bin/encoder?USER=admin&PWD=123456&MOVE=DOWNLEFT,3";
$self->sendCmd( $cmd );
}

sub moveMap
{
my $self = shift;
my $params = shift;
my $xcoord = $self->getParam( $params, 'xcoord' );
my $ycoord = $self->getParam( $params, 'ycoord' );
Debug( "Move Map to $xcoord,$ycoord" );
my $cmd = "/axis-cgi/com/ptz.cgi?center=$xcoord,$ycoord&imagewidth=".$self->{Monitor}->{Width}."&imageheight=".$self->{Monitor}->{Height};
$self->sendCmd( $cmd );
}

sub moveRelUp
{
my $self = shift;
my $params = shift;
my $step = $self->getParam( $params, 'tiltstep' );
Debug( "Step Up $step" );
my $cmd = "/cgi-bin/encoder?USER=admin&PWD=123456&MOVE=UP,$step";
$self->sendCmd( $cmd );
}

sub moveRelDown
{
my $self = shift;
my $params = shift;
my $step = $self->getParam( $params, 'tiltstep' );
Debug( "Step Down $step" );
my $cmd = "/cgi-bin/encoder?USER=admin&PWD=123456&MOVE=DOWN,$step";
$self->sendCmd( $cmd );
}

sub moveRelLeft
{
my $self = shift;
my $params = shift;
my $step = $self->getParam( $params, 'panstep' );
Debug( "Step Left $step" );
my $cmd = "/cgi-bin/encoder?USER=admin&PWD=123456&MOVE=left,$step";
$self->sendCmd( $cmd );
}

sub moveRelRight
{
my $self = shift;
my $params = shift;
my $step = $self->getParam( $params, 'panstep' );
Debug( "Step Right $step" );
my $cmd = "/cgi-bin/encoder?USER=admin&PWD=123456&MOVE=RIGHT,$step";
$self->sendCmd( $cmd );
}

sub moveRelUpRight
{
my $self = shift;
my $params = shift;
my $panstep = $self->getParam( $params, 'panstep' );
my $tiltstep = $self->getParam( $params, 'tiltstep' );
Debug( "Step Up/Right $tiltstep/$panstep" );
my $cmd = "/cgi-bin/encoder?USER=admin&PWD=123456&MOVE=UPRIGHT,$panstep, $tiltstep";
$self->sendCmd( $cmd );
}

sub moveRelUpLeft
{
my $self = shift;
my $params = shift;
my $panstep = $self->getParam( $params, 'panstep' );
my $tiltstep = $self->getParam( $params, 'tiltstep' );
Debug( "Step Up/Left $tiltstep/$panstep" );
my $cmd = "/cgi-bin/encoder?USER=admin&PWD=123456&MOVE=UPLEFT,$panstep,$tiltstep";
$self->sendCmd( $cmd );
}

sub moveRelDownRight
{
my $self = shift;
my $params = shift;
my $panstep = $self->getParam( $params, 'panstep' );
my $tiltstep = $self->getParam( $params, 'tiltstep' );
Debug( "Step Down/Right $tiltstep/$panstep" );
my $cmd = "/cgi-bin/encoder?USER=admin&PWD=123456&MOVE=downright,$panstep,$tiltstep";
$self->sendCmd( $cmd );
}

sub moveRelDownLeft
{
my $self = shift;
my $params = shift;
my $panstep = $self->getParam( $params, 'panstep' );
my $tiltstep = $self->getParam( $params, 'tiltstep' );
Debug( "Step Down/Left $tiltstep/$panstep" );
my $cmd = "/cgi-bin/encoder?USER=admin&PWD=123456&MOVE=UP,$panstep,$tiltstep";
$self->sendCmd( $cmd );
}

sub zoomRelTele
{
my $self = shift;
my $params = shift;
my $step = $self->getParam( $params, 'step' );
Debug( "Zoom Tele" );
my $cmd = "/axis-cgi/com/ptz.cgi?rzoom=$step";
$self->sendCmd( $cmd );
}

sub zoomRelWide
{
my $self = shift;
my $params = shift;
my $step = $self->getParam( $params, 'step' );
Debug( "Zoom Wide" );
my $cmd = "/axis-cgi/com/ptz.cgi?rzoom=-$step";
$self->sendCmd( $cmd );
}

sub focusRelNear
{
my $self = shift;
my $params = shift;
my $step = $self->getParam( $params, 'step' );
Debug( "Focus Near" );
my $cmd = "/axis-cgi/com/ptz.cgi?rfocus=-$step";
$self->sendCmd( $cmd );
}

sub focusRelFar
{
my $self = shift;
my $params = shift;
my $step = $self->getParam( $params, 'step' );
Debug( "Focus Far" );
my $cmd = "/axis-cgi/com/ptz.cgi?rfocus=$step";
$self->sendCmd( $cmd );
}

sub focusAuto
{
my $self = shift;
Debug( "Focus Auto" );
my $cmd = "/axis-cgi/com/ptz.cgi?autofocus=on";
$self->sendCmd( $cmd );
}

sub focusMan
{
my $self = shift;
Debug( "Focus Manual" );
my $cmd = "/axis-cgi/com/ptz.cgi?autofocus=off";
$self->sendCmd( $cmd );
}

sub irisRelOpen
{
my $self = shift;
my $params = shift;
my $step = $self->getParam( $params, 'step' );
Debug( "Iris Open" );
my $cmd = "/axis-cgi/com/ptz.cgi?riris=$step";
$self->sendCmd( $cmd );
}

sub irisRelClose
{
my $self = shift;
my $params = shift;
my $step = $self->getParam( $params, 'step' );
Debug( "Iris Close" );
my $cmd = "/axis-cgi/com/ptz.cgi?riris=-$step";
$self->sendCmd( $cmd );
}

sub irisAuto
{
my $self = shift;
Debug( "Iris Auto" );
my $cmd = "/axis-cgi/com/ptz.cgi?autoiris=on";
$self->sendCmd( $cmd );
}

sub irisMan
{
my $self = shift;
Debug( "Iris Manual" );
my $cmd = "/axis-cgi/com/ptz.cgi?autoiris=off";
$self->sendCmd( $cmd );
}

sub presetClear
{
my $self = shift;
my $params = shift;
my $preset = $self->getParam( $params, 'preset' );
Debug( "Clear Preset $preset" );
my $cmd = "/axis-cgi/com/ptz.cgi?removeserverpresetno=$preset";
$self->sendCmd( $cmd );
}

sub presetSet
{
my $self = shift;
my $params = shift;
my $preset = $self->getParam( $params, 'preset' );
Debug( "Set Preset $preset" );
my $cmd = "/axis-cgi/com/ptz.cgi?setserverpresetno=$preset";
$self->sendCmd( $cmd );
}

sub presetGoto
{
my $self = shift;
my $params = shift;
my $preset = $self->getParam( $params, 'preset' );
Debug( "Goto Preset $preset" );
my $cmd = "/axis-cgi/com/ptz.cgi?gotoserverpresetno=$preset";
$self->sendCmd( $cmd );
}

sub presetHome
{
my $self = shift;
Debug( "Home Preset" );
my $cmd = "/axis-cgi/com/ptz.cgi?move=home";
$self->sendCmd( $cmd );
}

1;
__END__
# Below is stub documentation for your module. You'd better edit it!

=head1 NAME

ZoneMinder::Database - Perl extension for blah blah blah

=head1 SYNOPSIS

use ZoneMinder::Database;
blah blah blah

=head1 DESCRIPTION

Stub documentation for ZoneMinder, created by h2xs. It looks like the
author of the extension was negligent enough to leave the stub
unedited.

Blah blah blah.

=head2 EXPORT

None by default.



=head1 SEE ALSO

Mention other useful documentation such as the documentation of
related modules or operating system documentation (such as man pages
in UNIX), or any relevant external documentation such as RFCs or
standards.

If you have a mailing list set up for your module, mention it here.

If you have a web site set up for your module, mention it here.

=head1 AUTHOR

Philip Coombes, Ephilip.coombes@zoneminder.comE

=head1 COPYRIGHT AND LICENSE

Copyright (C) 2001-2008 Philip Coombes

This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself, either Perl version 5.8.3 or,
at your option, any later version of Perl 5 you may have available.


=cut

Once copied save it and open your Options in Zoneminder - Mark and Save the
> OPT_CONTROL Support controllable (e.g. PTZ) cameras

The open your monitor settings again and there you will find a new "Control option" added up.

Just modify the settings as follows:
Controllable > *Mark this field*
Control Type: AXIS API V2
Control Device : * Just keep this blank*
Control Address: 192.168.0.101 (IP of your cam)
Auto Stop Timeout: 10
Track Motion: (feel this doesnt have any significance now)
Track Delay: (5) (feel this doesnt have any significance now)
Return Location: None (feel this doesnt have any significance now)
Return delay: 3 (feel this doesnt have any significance now)

Also just go to the AXIS page by clicking the 'edit' near control type and
> on the pan page just modify the "Max Pan Step" to 5.
> on the tilt page just modify the "Max Tilt Step" to 5.

Thatz it.... Just save and go to your monitor page. On top you'll find a Control option. Click there... You shall find some conrol arrow below with which you can move your PTZ camera !!!!!

********************************************************************************
Just note that this is a quick work around and due to that it doesnt contain any support other than the pan and tilt functionality. Meanwhile i'll try to come up with a script soon so that the camera shall work with its full functionality in a Linux (Zoneminder) environment.
*********************************************************************************

A self explanatory program to understand server socket program in C

/* A simple server in the internet domain using TCP
The port number is passed as an argument */

//header file contains declarations used in most input and output
#include <stdio.h>

//This header file contains definitions of a number of data types
//used in system calls.These types are used in the next two include files.
#include <sys/types.h>

//The header file socket.h includes a number of definitions of structures needed for sockets.
#include <sys/socket.h>


//The header file in.h contains constants and structures needed for internet domain addresses.
#include <netinet/in.h>

//Exit(1) etc are defined in this header file
#include <stdlib.h>

//bzero etc are defined under this header file
#include <string.h>

// This function is called when a system call fails. It displays a message
//about the error on stderr and then aborts the program.
void error(char *msg)
{
perror(msg);
exit(1);
}

int main(int argc, char *argv[])
{
//sockfd and newsockfd are file descriptors, i.e. array subscripts into the file descriptor table .
//These two variables store the values returned by the socket system call and the accept system call.
//portno stores the port number on which the server accepts connections.
//clilen stores the size of the address of the client. This is needed for the accept system call.
int sockfd, newsockfd, portno, clilen;

//The server reads characters from the socket connection into this buffer.
char buffer[256];

//A sockaddr_in is a structure containing an internet address. This structure is defined in netinet/in.h.
//Here is the definition:
// struct sockaddr_in
// {
// short sin_family; /* must be AF_INET */
// u_short sin_port;
// struct in_addr sin_addr;
// char sin_zero[8]; /* Not used, must be zero */
// };
//An in_addr structure, defined in the same header file, contains only one field, a unsigned long called s_addr.
//The variable serv_addr will contain the address of the server, and
//cli_addr will contain the address of the client which connects to the server.
struct sockaddr_in serv_addr, cli_addr;

//n is the return value for the read() and write() calls; i.e. it contains the number of characters read or written
int n;

// This is used for modifying socket options - Details is given later
int on, ret;

//The user needs to pass in the port number on which the server will accept connections as an argument.
//This code displays an error message if the user fails to do this.
if (argc < 2) {
fprintf(stderr,"ERROR, no port provided\n");
exit(1);
}
//The socket() system call creates a new socket. It takes three arguments.
//The first is the address domain of the socket.
//Recall that there are two possible address domains, the unix domain for
//two processes which share a common file system, and the Internet domain
//for any two hosts on the Internet. The symbol constant AF_UNIX is used for the former,
//and AF_INET for the latter (there are actually many other options
//which can be used here for specialized purposes).
//The second argument is the type of socket. Recall that there are two choices here,
//a stream socket in which characters are read in a continuous stream as if from a file or pipe,
//and a datagram socket, in which messages are read in chunks.
//The two symbolic constants are SOCK_STREAM and SOCK_DGRAM.
//The third argument is the protocol. If this argument is zero
//(and it always should be except for unusual circumstances),
//the operating system will choose the most appropriate protocol.
//It will choose TCP for stream sockets and UDP for datagram sockets.
//The socket system call returns an entry into the file descriptor table (i.e. a small integer).
//This value is used for all subsequent references to this socket.
// If the socket call fails, it returns -1.
//In this case the program displays and error message and exits.
//However, this system call is unlikely to fail.
//This is a simplified description of the socket call;
//there are numerous other choices for domains and types,
//but these are the most common.
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0)
error("ERROR opening socket");

//The function bzero() sets all values in a buffer to zero. It takes two arguments,
//the first is a pointer to the buffer and the second is the size of the buffer.
//Thus, this line initializes serv_addr to zeros.
bzero((char *) &serv_addr, sizeof(serv_addr));

//The port number on which the server will listen for connections is passed in as an argument,
//and this statement uses the atoi() function to convert this from a string of digits to an integer.
portno = atoi(argv[1]);

//The variable serv_addr is a structure of type struct sockaddr_in. This structure has four fields.
//The first field is short sin_family, which contains a code for the address family.
//It should always be set to the symbolic constant AF_INET.
serv_addr.sin_family = AF_INET;

//The third field of sockaddr_in is a structure of type struct in_addr which contains only a
//single field unsigned long s_addr. This field contains the IP address of the host.
//For server code, this will always be the IP address of the machine on which the server is running,
//and there is a symbolic constant INADDR_ANY which gets this address.
serv_addr.sin_addr.s_addr = INADDR_ANY;

//The second field of serv_addr is unsigned short sin_port, which contain the port number.
//However, instead of simply copying the port number to this field,
//it is necessary to convert this to network byte order using the function htons() which
//converts a port number in host byte order to a port number in network byte order.
serv_addr.sin_port = htons(portno);

//The bind() system call binds a socket to an address, in this case the address of the
//current host and port number on which the server will run. It takes three arguments,
//the socket file descriptor, the address to which is bound, and the size of the address
//to which it is bound. The second argument is a pointer to a structure of type sockaddr,
//but what is passed in is a structure of type sockaddr_in, and so this must be cast to the correct type.
//This can fail for a number of reasons, the most obvious being that
//this socket is already in use on this machine.
if (bind(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0)
error("ERROR on binding");

//The listen system call allows the process to listen on the socket for connections.
//The first argument is the socket file descriptor, and the second is the size of the backlog queue,
//i.e., the number of connections that can be waiting while the process is handling a particular connection.
//This should be set to 5, the maximum size permitted by most systems. If the first argument is a valid socket,
//this call cannot fail, and so the code doesn't check for errors.
listen(sockfd,5);

//The accept() system call causes the process to block until a client connects to the server.
//Thus, it wakes up the process when a connection from a client has been successfully established.
//It returns a new file descriptor, and all communication on this connection should be done using the
//new file descriptor. The second argument is a reference pointer to the address of the client on the
//other end of the connection, and the third argument is the size of this structure.
clilen = sizeof(cli_addr);
newsockfd = accept(sockfd,(struct sockaddr *) &cli_addr, &clilen);
if (newsockfd < 0)
error("ERROR on accept");

//Note that we would only get to this point after a client has successfully connected to our server.
//This code initializes the buffer using the bzero() function, and then reads from the socket.
//Note that the read call uses the new file descriptor, the one returned by accept(), not the original
//file descriptor returned by socket(). Note also that the read() will block until there is something
//for it to read in the socket, i.e. after the client has executed a write().
//It will read either the total number of characters in the socket or 255,
//whichever is less, and return the number of characters read.
(buffer,256);
n = read(newsockfd,buffer,255);
if (n < 0)
error("ERROR reading from socket");
printf("Here is the message: %s\n",buffer);

//Once a connection has been established, both ends can both read and write to the connection.
//Naturally, everything written by the client will be read by the server, and everything written
//by the server will be read by the client. This code simply writes a short message to the client.
//The last argument of write is the size of the message.
n = write(newsockfd,"I got your message",18);
if (n < 0) error("ERROR writing to socket");

//This terminates main and thus the program. Since main was declared to be of type int as specified
//by the ascii standard, some compilers complain if it does not return anything.
return 0;
}