PowerShell cmdlet of the Day : Test-Connection

Ping! I can bet, that you use this command almost daily. We use Ping.exe to test networking by pinging IP Addresses or hostnames. If the reply comes then we know networking is working fine and if we get RTO's , then we know, networking is not working.

In PowerShell we have a cmdlet Test-Connection which does the same.

The usage is simple, type the Cmdlet Test-Connection and in -Count parameter provide the numbers of Pings you want to send.

Test-Connection 8.8.8.8 -Count 3


Cool!

Actually the most cool thing is , this cmdlet's -Quiet switch parameter.

When we provide the -Quiet parameter, the output comes in True or False ( Awesome!!!). If your  IP/Host is reachable , then the output result will be True, otherwise it will be False.  This comes quite handy when you need to do some network availability checks in to your script.

:)

With Regards.

Aman Dhally

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Powershell Scripting Techniques : Using While in the Scripts to wait for Network Connection to be Establish.

Hi,
In any scripting language, the one of the  important things are techniques.
You can call it scripting techniques.
Sometime when you are writing scripts, there are some  certain problems come , and to solve them we need to add a special logics and special techniques to handle them.
Same thing was happen to me, i was writing a script and that script has to run every time users logon, and that script require a server to be available before running the script.
Flow Chart.
The logic is something like below flowchart.

How i solve it.
I solved it using WHILE  script code.
I have added Comments to the below script code, which make it self explanatory.

# Setting bit as False First
$bit = $false
# running while.
while ( $bit -eq $false ) 
        
        {
        # just a notification
        Write-Host 'Checking Internet Connection.' -ForegroundColor 'Yellow'
        
        # Testing Network Connection and storing it in to a vraible
        # when we use -QUIET Parameter with Test-Connection, it stored the value in 
        # true or false
        $testInternetConnectivity = Test-Connection -Count 3 "www.google.com" -Quiet    
        
        # Test-Connection CMDLET return output in TRUE and False
        # we are assigning the output of $testInternetConnectivity to the $bit Variable
        $bit =     $testInternetConnectivity
        
        #if the $bit is false then 
        if ( $testInternetConnectivity -ne $true) 
            {
            # show notifications
            Write-Host 'Please check your connection, I am not able to Ping www.google.com.'
            # just adding a new blank line
            "`n" 

#sleeping for 10 Seconds

Start-Sleep 10

} #end of IF


} # end of while
# if the $bit is $true , then we are good to go.
if ( $bit -eq $true )
{
# notifications
"`n"
Write-Host 'Internet is Pingable, we are good to go.' -ForegroundColor 'Green'

} #end of IF

# end of the script

You can also download the script code from this link :

Download Link : http://gallery.technet.microsoft.com/scriptcenter/Keep-Testing-Internet-f5c29243

Screenshots

I run the script and it found the “google.com” and give us an notification that Internet is Pingable.



I have disconnected my laptop from internet and run the script, you can check it is continuously running.



The internet is still disconnected and i run the script and it is showing that Internet connection is not there and in the middle I plugged in the LAN and you can see it found that google.com is working and  script is stopped.





What i want to accomplished?

My “Main” script run when users login to the laptop. This script copy a .xls file everyday to a server before user start working on a laptop.

The problem was, sometime user not plugged in the LAN cable and sometime they are not connected to WIFI. so most of the time script fails.

So , i want to write a code , by which this script always run until it found a backup server.

To accomplish it i wrote above script code.

Description

I am setting $bit variable to False first.

$bit = $false

Now I am running the lope that, util $bit is equal to false, keep try to ping google.com

while ( $bit -eq $false ) {

              Write-Host 'Checking Internet Connection.' -ForegroundColor 'Yellow'Now I am testing the connection with www.google.com and storing the result in to variable

$testInternetConnectivity = Test-Connection -Count 3 "www.google.com" –Quiet

Now , I am updating the $bit varable with the value in $testInternetConnectivity

$bit =        $testInternetConnectivity        

if ( $testInternetConnectivity -ne $true)

{

Write-Host 'Please check your connection, I am not able to Ping www.google.com.'

                     }

}

When $bit variable became to true the below script code will run.

if ( $bit -eq $true ) {

"`n”          

Write-Host 'Internet is Pingable, we are good to go.'  -ForegroundColor 'Green }

---------------------------------------

The only confusing bit in the script code is , how are storing the Test-Connection to “google.com” and true or false.

and the trick is when we use –Quiet parameter with Test-Connection cmdlet it give the output in true and false.

Please see the below screenshots are everything will be clear.

In below screenshot, i am storing the output of Test-Connection in to variable , without –Quiet parameter and it is give me full details of Source,Destination, IP address rather then giving me result in True or false.



Now, i added the –Quiet Parameter and you can see the result is shown is True now.



Same here.





Download Link : http://gallery.technet.microsoft.com/scriptcenter/Keep-Testing-Internet-f5c29243

I hope that this trick will help you.

Thanks

Aman Dhally