HttpClientConnectionTest.ps1

param (
    $RequestUrl = "http://127.0.0.1"
)

function Main
{
    $ErrorActionPreference = "Stop"
    Add-Type -AssemblyName System.Net.Http

    #Reuse connection
    $client = New-Object Net.Http.HttpClient

    $hostName = (New-Object Uri($RequestUrl)).Host
    $ipAddresses = [Net.Dns]::GetHostAddresses($hostName).IPAddressToString

    #Show Connection Count
    Write-Host ("Before: {0} connections" -f (Get-NetTCPConnection | where RemotePort -eq 80 | where { $_.RemoteAddress -in $ipAddresses }).Count)

    #Case 1:Don't dispose HttpClient　
    #　Connect　⇒ Established(100 seconds) ⇒ TIME_WAIT(120seconds)　⇒ Closed
    Invoke-HttpGetWithoutDispose -RequestUrl $RequestUrl > $null
    Write-Host "-----------------Test1-----------------"
    Write-Output (Get-NetTCPConnection | where RemotePort -eq 80 | where { $_.RemoteAddress -in $ipAddresses })

    #Case 2:Dispose HttpClient
    #　Connect ⇒ TIME_WAIT(120seconds)　⇒ Closed
    Invoke-HttpGetWithDispose -RequestUrl $RequestUrl > $null
    Write-Host "-----------------Test2-----------------"
    Write-Output (Get-NetTCPConnection | where RemotePort -eq 80 | where { $_.RemoteAddress -in $ipAddresses })

    #Case 3:With Connection:Close header(Dont' call dispose)
    #　Connect ⇒ Closed
    Invoke-HttpGetWithConnectionClose -RequestUrl $RequestUrl > $null
    Write-Host "-----------------Test3-----------------"
    Write-Output (Get-NetTCPConnection | where RemotePort -eq 80 | where { $_.RemoteAddress -in $ipAddresses })

    #Report port status every 10 seconds(total 240 seconds)
    $sw = [Diagnostics.Stopwatch]::StartNew()
    #TODO: Use Timer callback to check status
    
    foreach ($i in 0..24)
    {
        Write-Host ("-----------------Port status after {0:f1} seconds-----------------" -f ($sw.Elapsed.TotalSeconds))
        Write-Output (Get-NetTCPConnection | where RemotePort -eq 80 | where { $_.RemoteAddress -in $ipAddresses })
        sleep 10 #not exact delay
    }
}

function Invoke-HttpGetWithoutDispose([string] $RequestUrl)
{
    $client = New-Object Net.Http.HttpClient
    $task = $client.GetAsync($RequestUrl)
    $task.Wait()
    return $task.Result
}

function Invoke-HttpGetWithDispose([string] $RequestUrl)
{
    $client = New-Object Net.Http.HttpClient
    $task = $client.GetAsync($RequestUrl)
    $task.Wait()
    $client.Dispose()
    return $task.Result
}

function Invoke-HttpGetWithConnectionClose([string] $RequestUrl)
{
    $client = New-Object Net.Http.HttpClient
    $client.DefaultRequestHeaders.ConnectionClose = $true
    $task = $client.GetAsync($RequestUrl)
    $task.Wait()
    #$client.Dispose()  #Not Dispose
    return $task.Result
}

Main