This function runs netstat on a local or remote system and filters the results by process name, address, port, protocol or state if specified.

function Get-NetworkStatistics {
    <#
    .SYNOPSIS
        Display current TCP/IP connections for local or remote system.

    .FUNCTIONALITY
        Computers

    .DESCRIPTION
        Display current TCP/IP connections for local or remote system.  Includes
        the process ID (PID) and process name for each connection. If the port
        is not yet established, the port number is shown as an asterisk (*).

    .PARAMETER ProcessName
        Gets connections by the name of the process. The default value is '*'.

    .PARAMETER Port
        The port number of the local computer or remote computer. The default
        value is '*'.

    .PARAMETER Address
        Gets connections by the IP address of the connection, local or remote.
        Wildcard is supported. The default value is '*'.

    .PARAMETER Protocol
        The name of the protocol (TCP or UDP). The default value is '*' (all)

    .PARAMETER State
        Indicates the state of a TCP connection. The possible states are as follows:

        Closed       - The TCP connection is closed.
        Close_Wait   - The local endpoint of the TCP connection is waiting for a connection termination request from the local user.
        Closing      - The local endpoint of the TCP connection is waiting for an acknowledgement of the connection termination request sent previously.
        Delete_Tcb   - The transmission control buffer (TCB) for the TCP connection is being deleted.
        Established  - The TCP handshake is complete. The connection has been established and data can be sent.
        Fin_Wait_1   - The local endpoint of the TCP connection is waiting for a connection termination request from the remote endpoint or for an acknowledgement of the connection termination request sent previously.
        Fin_Wait_2   - The local endpoint of the TCP connection is waiting for a connection termination request from the remote endpoint.
        Last_Ack     - The local endpoint of the TCP connection is waiting for the final acknowledgement of the connection termination request sent previously.
        Listen       - The local endpoint of the TCP connection is listening for a connection request from any remote endpoint.
        Syn_Received - The local endpoint of the TCP connection has sent and received a connection request and is waiting for an acknowledgment.
        Syn_Sent     - The local endpoint of the TCP connection has sent the remote endpoint a segment header with the synchronize (SYN) control bit set and is waiting for a matching connection request.
        Time_Wait    - The local endpoint of the TCP connection is waiting for enough time to pass to ensure that the remote endpoint received the acknowledgement of its connection termination request.
        Unknown      - The TCP connection state is unknown.

        Values are based on the TcpState Enumeration:
        http://msdn.microsoft.com/en-us/library/system.net.networkinformation.tcpstate%28VS.85%29.aspx

        Cookie Monster - modified these to match netstat output per here:
        http://support.microsoft.com/kb/137984

    .PARAMETER ComputerName
        If defined, run this command on a remote system via WMI.
        \\computername\c$\netstat.txt is created on that system and the results
        returned here

    .PARAMETER ShowHostNames
        If specified, will attempt to resolve local and remote addresses.

    .PARAMETER tempFile
        Temporary file to store results on remote system.  Must be relative to
        remote system (not a file share).  Default is "C:\netstat.txt"

    .PARAMETER AddressFamily
        Filter by IP Address family: IPv4, IPv6, or the default, * (both).

        If specified, we display any result where both the localaddress and the
        remoteaddress is in the address family.

    .EXAMPLE
        Get-NetworkStatistics | Format-Table

    .EXAMPLE
        Get-NetworkStatistics iexplore -computername k-it-thin-02 -ShowHostNames | Format-Table

    .EXAMPLE
        Get-NetworkStatistics -ProcessName md* -Protocol tcp

    .EXAMPLE
        Get-NetworkStatistics -Address 192* -State LISTENING

    .EXAMPLE
        Get-NetworkStatistics -State LISTENING -Protocol tcp

    .EXAMPLE
        Get-NetworkStatistics -Computername Computer1, Computer2

    .EXAMPLE
        'Computer1', 'Computer2' | Get-NetworkStatistics

    .OUTPUTS
        System.Management.Automation.PSObject

    .NOTES
        Author: Shay Levy, code butchered by Cookie Monster
        Shay's Blog: http://PowerShay.com
        Cookie Monster's Blog: http://ramblingcookiemonster.github.io/

    .LINK
        http://gallery.technet.microsoft.com/scriptcenter/Get-NetworkStatistics-66057d71
    #>
    [OutputType('System.Management.Automation.PSObject')]
    [CmdletBinding()]
    param(

        [Parameter(Position=0)]
        [System.String]$ProcessName='*',

        [Parameter(Position=1)]
        [System.String]$Address='*',

        [Parameter(Position=2)]
        $Port='*',

        [Parameter(Position=3,
                   ValueFromPipeline = $True,
                   ValueFromPipelineByPropertyName = $True)]
        [System.String[]]$ComputerName=$env:COMPUTERNAME,

        [ValidateSet('*','tcp','udp')]
        [System.String]$Protocol='*',

        [ValidateSet('*','Closed','Close_Wait','Closing','Delete_Tcb','DeleteTcb','Established','Fin_Wait_1','Fin_Wait_2','Last_Ack','Listening','Syn_Received','Syn_Sent','Time_Wait','Unknown')]
        [System.String]$State='*',

        [switch]$ShowHostnames,

        [switch]$ShowProcessNames = $true,

        [System.String]$TempFile = "C:\netstat.txt",

        [validateset('*','IPv4','IPv6')]
        [string]$AddressFamily = '*'
    )

    begin{
        #Define properties
            $properties = 'ComputerName','Protocol','LocalAddress','LocalPort','RemoteAddress','RemotePort','State','ProcessName','PID'

        #store hostnames in array for quick lookup
            $dnsCache = @{}

    }

    process{

        foreach($Computer in $ComputerName) {

            #Collect processes
            if($ShowProcessNames){
                Try {
                    $processes = Get-Process -ComputerName $Computer -ErrorAction stop | select name, id
                }
                Catch {
                    Write-warning "Could not run Get-Process -computername $Computer.  Verify permissions and connectivity.  Defaulting to no ShowProcessNames"
                    $ShowProcessNames = $false
                }
            }

            #Handle remote systems
                if($Computer -ne $env:COMPUTERNAME){

                    #define command
                        [string]$cmd = "cmd /c c:\windows\system32\netstat.exe -ano >> $tempFile"

                    #define remote file path - computername, drive, folder path
                        $remoteTempFile = "\\{0}\{1}`${2}" -f "$Computer", (split-path $tempFile -qualifier).TrimEnd(":"), (Split-Path $tempFile -noqualifier)

                    #delete previous results
                        Try{
                            $null = Invoke-WmiMethod -class Win32_process -name Create -ArgumentList "cmd /c del $tempFile" -ComputerName $Computer -ErrorAction stop
                        }
                        Catch{
                            Write-Warning "Could not invoke create win32_process on $Computer to delete $tempfile"
                        }

                    #run command
                        Try{
                            $processID = (Invoke-WmiMethod -class Win32_process -name Create -ArgumentList $cmd -ComputerName $Computer -ErrorAction stop).processid
                        }
                        Catch{
                            #If we didn't run netstat, break everything off
                            Throw $_
                            Break
                        }

                    #wait for process to complete
                        while (
                            #This while should return true until the process completes
                                $(
                                    try{
                                        get-process -id $processid -computername $Computer -ErrorAction Stop
                                    }
                                    catch{
                                        $FALSE
                                    }
                                )
                        ) {
                            start-sleep -seconds 2
                        }

                    #gather results
                        if(test-path $remoteTempFile){

                            Try {
                                $results = Get-Content $remoteTempFile | Select-String -Pattern '\s+(TCP|UDP)'
                            }
                            Catch {
                                Throw "Could not get content from $remoteTempFile for results"
                                Break
                            }

                            Remove-Item $remoteTempFile -force

                        }
                        else{
                            Throw "'$tempFile' on $Computer converted to '$remoteTempFile'.  This path is not accessible from your system."
                            Break
                        }
                }
                else{
                    #gather results on local PC
                        $results = netstat -ano | Select-String -Pattern '\s+(TCP|UDP)'
                }

            #initialize counter for progress
                $totalCount = $results.count
                $count = 0

            #Loop through each line of results
                foreach($result in $results) {

                    $item = $result.line.split(' ',[System.StringSplitOptions]::RemoveEmptyEntries)

                    if($item[1] -notmatch '^\[::'){

                        #parse the netstat line for local address and port
                            if (($la = $item[1] -as [ipaddress]).AddressFamily -eq 'InterNetworkV6'){
                                $localAddress = $la.IPAddressToString
                                $localPort = $item[1].split('\]:')[-1]
                            }
                            else {
                                $localAddress = $item[1].split(':')[0]
                                $localPort = $item[1].split(':')[-1]
                            }

                        #parse the netstat line for remote address and port
                            if (($ra = $item[2] -as [ipaddress]).AddressFamily -eq 'InterNetworkV6'){
                                $remoteAddress = $ra.IPAddressToString
                                $remotePort = $item[2].split('\]:')[-1]
                            }
                            else {
                                $remoteAddress = $item[2].split(':')[0]
                                $remotePort = $item[2].split(':')[-1]
                            }

                        #Filter IPv4/IPv6 if specified
                            if($AddressFamily -ne "*")
                            {
                                if($AddressFamily -eq 'IPv4' -and $localAddress -match ':' -and $remoteAddress -match ':|\*' )
                                {
                                    #Both are IPv6, or ipv6 and listening, skip
                                    Write-Verbose "Filtered by AddressFamily:`n$result"
                                    continue
                                }
                                elseif($AddressFamily -eq 'IPv6' -and $localAddress -notmatch ':' -and ( $remoteAddress -notmatch ':' -or $remoteAddress -match '*' ) )
                                {
                                    #Both are IPv4, or ipv4 and listening, skip
                                    Write-Verbose "Filtered by AddressFamily:`n$result"
                                    continue
                                }
                            }

                        #parse the netstat line for other properties
                            $procId = $item[-1]
                            $proto = $item[0]
                            $status = if($item[0] -eq 'tcp') {$item[3]} else {$null}

                        #Filter the object
                            if($remotePort -notlike $Port -and $localPort -notlike $Port){
                                write-verbose "remote $Remoteport local $localport port $port"
                                Write-Verbose "Filtered by Port:`n$result"
                                continue
                            }

                            if($remoteAddress -notlike $Address -and $localAddress -notlike $Address){
                                Write-Verbose "Filtered by Address:`n$result"
                                continue
                            }

                            if($status -notlike $State){
                                Write-Verbose "Filtered by State:`n$result"
                                continue
                            }

                            if($proto -notlike $Protocol){
                                Write-Verbose "Filtered by Protocol:`n$result"
                                continue
                            }

                        #Display progress bar prior to getting process name or host name
                            Write-Progress  -Activity "Resolving host and process names"`
                                -Status "Resolving process ID $procId with remote address $remoteAddress and local address $localAddress"`
                                -PercentComplete (( $count / $totalCount ) * 100)

                        #If we are running showprocessnames, get the matching name
                            if($ShowProcessNames -or $PSBoundParameters.ContainsKey -eq 'ProcessName'){

                                #handle case where process spun up in the time between running get-process and running netstat
                                if($procName = $processes | Where {$_.id -eq $procId} | select -ExpandProperty name ){ }
                                else {$procName = "Unknown"}

                            }
                            else{$procName = "NA"}

                            if($procName -notlike $ProcessName){
                                Write-Verbose "Filtered by ProcessName:`n$result"
                                continue
                            }

                        #if the showhostnames switch is specified, try to map IP to hostname
                            if($showHostnames){
                                $tmpAddress = $null
                                try{
                                    if($remoteAddress -eq "127.0.0.1" -or $remoteAddress -eq "0.0.0.0"){
                                        $remoteAddress = $Computer
                                    }
                                    elseif($remoteAddress -match "\w"){

                                        #check with dns cache first
                                            if ($dnsCache.containskey( $remoteAddress)) {
                                                $remoteAddress = $dnsCache[$remoteAddress]
                                                write-verbose "using cached REMOTE '$remoteAddress'"
                                            }
                                            else{
                                                #if address isn't in the cache, resolve it and add it
                                                    $tmpAddress = $remoteAddress
                                                    $remoteAddress = [System.Net.DNS]::GetHostByAddress("$remoteAddress").hostname
                                                    $dnsCache.add($tmpAddress, $remoteAddress)
                                                    write-verbose "using non cached REMOTE '$remoteAddress`t$tmpAddress"
                                            }
                                    }
                                }
                                catch{ }

                                try{

                                    if($localAddress -eq "127.0.0.1" -or $localAddress -eq "0.0.0.0"){
                                        $localAddress = $Computer
                                    }
                                    elseif($localAddress -match "\w"){
                                        #check with dns cache first
                                            if($dnsCache.containskey($localAddress)){
                                                $localAddress = $dnsCache[$localAddress]
                                                write-verbose "using cached LOCAL '$localAddress'"
                                            }
                                            else{
                                                #if address isn't in the cache, resolve it and add it
                                                    $tmpAddress = $localAddress
                                                    $localAddress = [System.Net.DNS]::GetHostByAddress("$localAddress").hostname
                                                    $dnsCache.add($localAddress, $tmpAddress)
                                                    write-verbose "using non cached LOCAL '$localAddress'`t'$tmpAddress'"
                                            }
                                    }
                                }
                                catch{ }
                            }

                        #Write the object
                            New-Object -TypeName PSObject -Property @{
                                ComputerName = $Computer
                                PID = $procId
                                ProcessName = $procName
                                Protocol = $proto
                                LocalAddress = $localAddress
                                LocalPort = $localPort
                                RemoteAddress =$remoteAddress
                                RemotePort = $remotePort
                                State = $status
                            } | Select-Object -Property $properties

                        #Increment the progress counter
                            $count++
                    }
                }
        }
    }
}