Internet not working: some troubleshooting tips

Connecting to internet sometime becomes so frustrating that you curse your laptop. Sometimes I have spend hours to connect to internet specially when I switch between multiple wifi networks.
Here are some common troubleshooting tips when connecting to wifi network.

Before starting, first check if every thing is on, you know, your wifi router in on, WLAN is activated, wifi adapter of your laptop is enabled. If everything is fine, try to Switch off modem and all internet devices for at least one minute and then switch on.  Then roll up your sleeves and try following options:

A. FIRST THING TO DO: Auto repair
first go automatic, simply right click on the network icon at right bottom of you screen (near the clock) and select "Diagnose and Repair" or you may have something similar like "Troubleshoot". This will take care of most of the problems.
You can also find this option from Control Panel > Network and Sharing Center.

After this open Network and Sharing Center and it still shows cross in your network map. click on that cross, it will also repair.

B. NOT CONNECTING TO WIFI NETWORK
1. check name of the network, if it is same as an old network you were connected to, there would be a conflict. E.g.: If you have your home network named DLink and the new network also has same name, it wont connect until you delete old network setting. Better keep different names for different networks. Make it personalised but dont make it too personal as it is being broadcast. ALWAYS PUT A PASSWORD (WPA key) on your wifi network.
 Go to Network > Network & Sharing Center > Manage Wireless Network
delete old network OR update WPA password for same name

C. wifi Network not in the list of available network
1. check your router, there is button which enable/disable WLAN
2. if you know how to configure router setting, check WLAN settings
3. enable/disable wife adapter of your laptop

D. connected to network but INTERNET NOT WORKING
This should be taken care by option A of "Diagnose and Repair".
After that try these
1. open command prompt ("cmd" in run menu) in admin mode (Run As Administrator)
try these ipconfig commands
type "ipconfig /help" to know what this command does.  To reset ip address try these. first command will show current ip settings
1. ipconfig
2. ipconfig /all
3. ipconfig /release
4. ipconfig /renew

DNS not working. Can't open even www.google.com even when internet connection seems fine. This is my recent discovery , when net is well connected but cant resolve DNS
try  this
1. ipconfig /flushdns
2. ipconfig /registerdns

you can try playing with services, restarting DHCP, DNS, Network connection services etc. This may help sometime.

(some good options here for DNS error etc
https://www.wiknix.com/how-to-fix-err_connection_refused-in-chrome/
use these commands
ipconfig /release
ipconfig /all
ipconfig /flushdns
ipconfig /renew

netsh int ip set dns
netsh winsock reset
then restart computer
)

E. Net is connected but browser giving SECURITY CERTIFICATE ERROR
1. check the date and time setting. this is most common problem in older system that are unable to sync the clock properly.
Click on clock (right bottom of your screen) , Set the correct date and time by changing date and time setting.
Go to Internet Time > Change settings > update time

F. Sharing internet from mobile phone
USB internet is as costly as mobile data. So better use your mobiles "hot-spot", "internet tethering" or "internet sharing" options and use it as a wifi router. just play around "settings" in your mobile and you will find some option to share you mobile's data connection. Dont forget to put a password for your network.

This should help. Still try google for the specific problem you have using other device which is still connected to internet. You will find some help. Its not rocket science after all. :)

Print calendar program in C

/* prog to print calendar of any month in a given year by pradeep */
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

void main()
{
int firstdayofyear(int);
int firstdayofmonth(int,int);
int leapckeck(int);

int i,j,yr=0,date=0,m=0;
int f=0,fdoy=0;

char *mon[]={"Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec"};
char day[]={'S','M','T','W','T','F','S'};
int dim[]={31,28,31,30,31,30,31,31,30,31,30,31};

/*
dim  is days in month
jan 31, feb 28/29, mar 31, apr 30, may 31, jun 30, jul 31, aug 31, sep 30, oct 31, nov 30, dec 31
*/

printf("enter month (1-12) and yr\n");
scanf("%d %d",&m,&yr);

printf("you enetered %d %d\n",m,yr);

if(leapcheck(yr))
dim[1]++;
/* printf("days in feb %d",dim[1]);  */

/* find first of month and year  */
fdoy=firstdayofyear(yr);
f=firstdayofmonth(fdoy,m);

if((m>2)&&(dim[1]==29))
f++;  /* adding on odd day for feb of leap yr for month later than feb*/

if((m>0)&&(m<13))
{
 printf("\t\t    \3%s %d\3 \n",mon[m-1],yr);
}
else
{
 printf("wrong month, printing for Jan");
 m=1;
}

/* print day header */
for(i=0;i<7;i++)
printf("%c \t",day[i]);
printf("\n");

/* starting from first day */
for(j=0;j<f;j++)
printf("\t");


for(date=1;date<=dim[m-1];date++)
{
 if((date+f-1)%7==0)
 printf("\n");
 printf("%d \t",date);
}

}/* end of main function */

/* function to check leap year */
int leapcheck(int yr)
{
 int leap=0;
 if(yr%100==0)
 {
  if(yr%400==0)
  {
/*  printf("%d is leap yr",yr); */
  leap =1;
  }
  else
  {
/*  printf("%d is not a leap yr",yr);   */
  }
 }
 else if(yr%4==0)
 {
/*  printf("%d is leap yr",yr);   */
  leap=1;
 }else
  {
/*  printf("%d is not a leap yr",yr);   */
 }
 return(leap);
}


/* function to find first day of the year */
int firstdayofyear(int year)
{

/*  printf("in year %d \n",year);   */

int oddyears=0,cents=0,leapys=0,odds=0,years=0;
years--;  /* cal odd days till last yr  */
oddyears=year%400;  /* calendar reset after 400 yrs, rest yrs odd days */
cents=oddyears/100;
odds=odds + cents*5;  /* 5 odd days in each century */
years=oddyears%100;
leapys=years/4;      /* leap yeras to add extra odd days */
odds = odds + leapys + years;
/*
printf("cents %d leapys %d, odds %d\n",cents,leapys,odds);
*/
return(odds%7);

}

/* function to find first day of the month */
int firstdayofmonth(int fdoy,int mon)
{
int i=0,odds=0;
/*
printf("fdoy is %d month is %d\n",fdoy,mon);
dim  is days in month
jan 31, feb 28/29, mar 31, apr 30, may 31, jun 30, jul 31, aug 31, sep 30, oct 31, nov 30, dec 31
*/

/* odd days in each month ,for feb we will adjust while printing there*/
int oddm[]={3,0,3,2,3,2,3,3,2,3,2,3};
for(i=1;i<mon;i++)
{
odds=odds+oddm[i-1];
}

odds=odds+fdoy;
/* printf("odds are %d \n",odds);  */
return(odds%7);
}

NPTEL : Online enginnering courses by IITs

The IITs have taken up an initiative of starting online teaching and thus have started offering course materials online for every engineering stream.

Many professors from all the IITs have provided course materials for each chapter and each subject..
Every Chapter has been described with diagrams and charts. Please spread this message to everyone, as many can benefit from this program taken up by the government and IIT.
1] Type the following address on internet explorer http://www.nptel.iitm.ac.in
2] Click on Courses http://www.nptel.iitm.ac.in/courses.php
The video courses are available on you tube http://youtube.com/iit
Please spread the word, so that this initiative benefits as many students as possible.
Its good to see such initiatives coming in India. MIT has a very good online course material website
http://www.nptel.iitm.ac.in/index.php
"Write to be understood, speak to be heard, read to grow."

for a misc blog....things we dont know.. and some keyboard shortcuts

Here are few interesting facts that are very usual to know but we are unaware!

Things we didn’t know (source: http://en.wikipedia.org/wiki/Backronym )

• SOS, the international distress signal is chosen solely for its easy recognizability in Morse code(...---...). The International Wireless Telegraph Convention makes no mention that it stands for "save our ship", "save our souls", or "send out succour".
In Morse code is S = … (3 dots), O = --- (3 dashes)

• ISO The International Organization for Standardization chose the three letters "ISO" as a short form of its name, based partly on the Greek word Isos which means equal. This has often been assumed to be an acronym for "International Standards Organization", even though the correct title of the organization is "International Organization for Standardization".

I will keep adding more things to this blog.

And here are few shortcuts for computer users:

. use F7 to activate cursor on web page
. use F11 for full screen
. use CTRL+ page up/down to move across sheets in MS Office excel
( this was really tough to find )

. To change tabs in Mozilla, double click on the top of the tab, and use arrow key
. use "windiff" in run command in windows to see file/directory differences.
. CTRL+G for jumping to page number ( in word or pdf)
. F6 to go to address bar in mozilla
. Window key + L to lock your PC.

More links to understand wireless

http://www.mobile-review.com/

For good understanding of all kinds of Protocols:
http://www.protocols.com

http://www.umtsworld.com/technology/overview.htm- This has a good overview tutorial on 3G UMTS

http://www.3g-generation.com/http://www.three-g.net/http://www.three-g.net/-
More useful links for 3G UMTS

http://www.privateline.com/Cellbasics/Cellbasics.html- For some cellular wireless basics

http://www.gsmworld.com/- Some general information on GSM

http://www.3gpp.org/- This has all the GSM/GPRS/EDGE/UMTS specifications

http://www.mobile-review.com/print.php?filename=/articles/2003/gsm-phones-en.shtml has very good illustration of basic concepts related to wireless and wireline communication system

http://www.privateline.com/PCS/PCS2.htm

http://www.privateline.com/wireless.html

http://www.cnp-wireless.com/cellular.html

www.gsmworld.com

GSM GPRS mobile communication

Hi! I have some useful links for understanding 3G mobile communication. To have a basic idea of GSM network, this IEEE paper will help you lot.
Overview of GSM Architecture and Protocol Stack

If You are interested in GPRS , you must visit this link..it has given very good images for a clear understanding of GSM-GPRS Network and Protocols Stack.
GSM Phase 2+ General Packet Radio Service GPRS: Architecture, Protocols, and Air Interface

And If you want to go in deep , then the best and most reliable are 3gPP standards. So go to www.3gpp.org and you'll find every thing here: 3G Specifications
Please do mail me for any query related to Mobile Communication. That will help me to go in deep and discover new areas..and if i know it...i will try to reply promptly.