Invoke-MetasysGetStream.ps1
|
# https://www.reddit.com/r/PowerShell/comments/g8p8ya/powershell_and_rest_serversent_events_api_sse_not/ function Invoke-MetasysGetStream { <# .SYNOPSIS Connects to the /stream resource on a Metasys site to listen for events .DESCRIPTION Some of the operations on a Metasys site can send events to a client. For example, one can sign up for Change of Value updates for an attribute value. Then whenever that attribute changes value, the client is notified. To do this requires a few steps. - Open two powershell terminals - In each establish a connection using Connect-MetasysAccount - In the first terminal, run Invoke-MetasysGetStream. In a short time you'll receive a hello event. The data in that event will be your stream id that you use to sign up for events. - In the second terminal, invoke an operation that supports subscriptions. For example, read the present value of an analog object and include the METASYS-SUBSCRIBE header with the value of your stream id. In the first terminal you should receive an object.values.update event with the current value of the object. - In the UI or in the second terminal, change the value of the attribute you read in the previous step. Within a short period of time you should see another object.values.update event with the new value. #> param ( # By default the event stream is just a stream of text. Use this switch to stream a collection of objects instead [switch]$ReturnObjects ) $token = [MetasysEnvVars]::getTokenAsPlainText() if ($null -eq $token ) { Write-Error "No connection to a Metasys site exists. Please connect using Connect-MetasysAccount" exit } $metasysHost = [MetasysEnvVars]::getSiteHost() $version = [MetasysEnvVars]::getVersion() $Url = "https://$metasysHost/api/v$version/stream" $request = [System.Net.WebRequest]::CreateHttp($Url) $request.Headers.Add("Authorization", "Bearer $token") $request.AllowReadStreamBuffering = $false $response = $request.GetResponse() $stream = $response.GetResponseStream() $encoding = [System.Text.Encoding]::UTF8 if ($ReturnObjects) { $parser = New-EventParser } while ($true) { [byte[]]$buffer = New-Object byte[] 2048 $length = $Stream.Read($buffer, 0, 2048) $text = $encoding.GetString($buffer, 0, $length) # We want to remove any trailing new line since the outputing of # $test is going to cause another new line to be sent anyway and # we want to avoid duplicated newlines if ($text.EndsWith("`r`n")) { $text = $text.Substring(0, $text.Length - 2) } elseif ($text.EndsWith("`n")) { $text = $text.Substring(0, $text.Length - 1) } if ($ReturnObjects) { # Split the text into lines and feed each to our event # parser $text -split '\r?\n' | ForEach-Object { &$parser -line $_ } } else { $text } } } Set-Alias -Name ims -Value Invoke-MetasysGetStream Export-ModuleMember -Alias "ims" Export-ModuleMember -Function "Invoke-MetasysGetStream" |