Open Ports

Linux

netstat works on windows and linux, but all of the flags/switches are not the same.

netstat

See everything:

netstat -tunlp

Filter specific ports:

netstat -tunlp | egrep ":80|:443"
tcp        0      0 0.0.0.0:80      0.0.0.0:*       LISTEN      9730/apache2
tcp        0      0 0.0.0.0:443     0.0.0.0:*       LISTEN      9730/apache2

netstat port watch

while true; do clear; netstat -tuln | grep ':443 '; sleep 2; done

ss port watch

ss -l | grep http
tcp    LISTEN    0         128		0.0.0.0:http		0.0.0.0:*
tcp    LISTEN    0         128		0.0.0.0:https		0.0.0.0:*

while true; do clear; ss -tuln | grep ':443 '; sleep 2; done

netcat port check

nc -v somesite.com 22
Connection to somesite.com (162.243.23.116) 22 port [tcp/ssh] succeeded!
SSH-2.0-OpenSSH_7.6p1 Ubuntu-4ubuntu0.7

nmap

nmap -sV -p 22,80 192.168.1.201

telnet

telnet 192.168.1.201 22

Windows

Show Matching Binary

as admin if you want to see the binary that is opening the port:

netstat -anotb | findstr :80

or as non-admin if you only need to see the open ports:

netstat -anot | findstr :80

netstat Port Watch

for /L %i in (0,0,0) do @cls && netstat -ano|find ":443" && @ping -n 1 -w 2000 224.0.0.0 >NUL && @cls

Powershell Port Watch

while ($true) { cls; netstat -ano | Select-String ":443"; Start-Sleep -Milliseconds 2000 }

Powershell TNC

Basic check looks like this:

Test-NetConnection -Computername "192.168.1.201" -Port 22

Monitoring looks like this:

while(1) {sleep -sec 2; Test-NetConnection -Computername "192.168.1.201" -Port 22 -Information Quiet}

Powershell 3 way Handshake

$client = new-object System.Net.Sockets.TcpClient
$result = $client.ConnectAsync("192.168.1.201","22").Wait(1500)
write-host -NoNewline "$(Get-Date)`t$result"

Powershell Port Scanner

<#

-----------------
DESCRIPTION
-----------------
Given a host and a list of ports, tells you if they are open/closed

SIMPLER ONELINER:
(cannot specify timeout or multiple ports, but does TCP Connect)
	PS> while(1) {sleep -sec 2; Test-NetConnection -Computername 'yourhost.com' -Port 443 -Information Quiet}

THIS VERSION:
Allows 1 host and multiple ports, colorizes output, measures time taken
(based on Chapmans code with a few adjustments because the timewait was annoying)

-----------------
OUTPUT:
-----------------
PS C:\Users\James\Desktop> &".\checkports.ps1" 'yourhost.com',22,80,443,3389
MM/DD/YYY HH:MM:SS      STAT    PORT    HOST            TIME TAKEN
12/09/2020 13:09:32     OPEN    22      yourhost.com     0.0491842
12/09/2020 13:09:34     OPEN    80      yourhost.com     0.0401987
12/09/2020 13:09:36     OPEN    443     yourhost.com     0.0426557
12/09/2020 13:09:40     FAIL    3389    yourhost.com     1.5036415


MM/DD/YYY HH:MM:SS      STAT    PORT    HOST            TIME TAKEN
12/09/2020 13:09:42     OPEN    22      yourhost.com     0.0436378
12/09/2020 13:09:44     OPEN    80      yourhost.com     0.0413645
12/09/2020 13:09:46     OPEN    443     yourhost.com     0.0415196
12/09/2020 13:09:49     FAIL    3389    yourhost.com     1.5025818


-----------------
INSTRUCTIONS:   
-----------------
CHECK PERMISSION:
Get-ExecutionPolicy -List

SET PERMISSION:
Set-ExecutionPolicy Unrestricted

SAVE AND RUN:
Save as "checkports.ps1"

USAGE:
	PS> & ".\checkports.ps1" "yourhost.com",21,22,80,443,3389


#>
[CmdletBinding()]
param(
	[Parameter(Mandatory=$False)]
	[string[]]$in=@()
)
if ( $PSBoundParameters.Values.Count -eq 0 ){ 
    write-host "USAGE:" -ForegroundColor Red
    write-host "`tPS> & '.\checkports.ps1' 'yourhost.com',21,22,80,443,3389" -ForegroundColor Red
    return
}


$h,$ps = $in


while(1){
	write-host "MM/DD/YYYY HH:MM:SS`tSTAT`tPORT`tHOST`t`tTIME TAKEN" -ForegroundColor Yellow		
	foreach ($p in $ps) {
		# measure it
		Measure-Command {
			
			# try a connection
			try {
				$client = new-object System.Net.Sockets.TcpClient
				$opened = $client.ConnectAsync($h,$p).Wait(1500)
				
				# if actively closed or fails timeout
				if($opened){
					$client.Close()
					write-host -NoNewline "$(Get-Date)`tOPEN`t$p`t$h`t" -ForegroundColor Green
				} else {
					write-host -NoNewline "$(Get-Date)`tFAIL`t$p`t$h`t" -ForegroundColor Red
				}
			}

			# default if it fails connect
			catch {
				write-host -NoNewline "$(Get-Date)`t????`t$p`t$h`t" -ForegroundColor Red
			}
		} | % TotalSeconds
	
		# wait 2 seconds between each port to prevent blocking
		Start-Sleep -Seconds 2
	}

	write-host "`n"
}