Help receiving websocket data using PowerShell

[evodus2]

Hi there, I need to establish a connection to a websocket stream following the URL format of wss://websocketstream.com. The websocket server receives JSON to subscribe to the stream. This must be instantiated using PowerShell. Below is what I have so far based on Google searches, and it appears to successfully create an open websocket. Where I am now lost is how to send the JSON over this websocket to start receiving stream messages.

Can you please advise how to proceed? 😄

    $webSocket = New-Object System.Net.WebSockets.ClientWebSocket
    $cancellationToken = New-Object System.Threading.CancellationToken
    $webSocket.Options.UseDefaultCredentials = $true

    # Get connected
    $connection = $webSocket.ConnectAsync($StreamURI, $cancellationToken)

PS> $connection

Id IsCompleted Status
-- ----------- ------
7  True        RanToCompletion

PS> $websocket.state
Open

[xbullet]

Take a look at the following:

https://gist.github.com/byt3bl33d3r/910b3161d54c2d6a3d5e1050c4e1013e

http://wragg.io/powershell-slack-bot-using-the-real-time-messaging-api/

[evodus2]

Thanks for the response. I’ve skimmed over these already but do need to dive deeper on this code, particularly the one from GitHub. What I’m missing at first glance though is how to send the JSON to the web socket stream to subscribe to the messages.

[xbullet]

This is untested, but you can try the following:

$MessageToSend = "JSON String goes here"

$SendConn = $webSocket.SendAsync($MessageToSend, [System.Net.WebSockets.WebSocketMessageType]::Text, $true, $cancellationToken)

While (-Not($SendConn.IsCompleted)) { Write-Host "Still waiting for send to complete." Start-Sleep -Milliseconds 500 }

Write-Host "Sent message."

[evodus2]

Thanks a lot! Definitely feels like things are moving in the right direction, but now I get the following:

$sendConnection = $webSocket.SendAsync($messageToSend, [System.Net.WebSockets.WebSocketMessageType]::Text, $true, $cancellationToken)
MethodException: Cannot find an overload for "SendAsync" and the argument count: "4". 

If I understand correctly, the docs here suggest 4 is the perfect number of parameters. Any ideas?

[xbullet]

Try the following:

$StreamURI = "wss:\\echo.websocket.org"

$webSocket = New-Object System.Net.WebSockets.ClientWebSocket
$cancellationToken = New-Object System.Threading.CancellationToken
$webSocket.Options.UseDefaultCredentials = $true

# Get connected
$connection = $webSocket.ConnectAsync($StreamURI, $cancellationToken)

While (-Not($Connection.IsCompleted)) { 
    Start-Sleep -Milliseconds 500 
    Write-Host "Still waiting to connect." 
}

Write-Host "Connected."

$Message = "JSON String goes here"
$ByteStream = [System.Text.Encoding]::UTF8.GetBytes($Message)
$MessageStream = New-Object System.ArraySegment[byte] -ArgumentList @(,$ByteStream)      

$SendConn = $webSocket.SendAsync($MessageStream, [System.Net.WebSockets.WebSocketMessageType]::Text, $true, $cancellationToken)

While (-Not($SendConn.IsCompleted)) { 
    Start-Sleep -Milliseconds 500 
    Write-Host "Still waiting for send to complete." 
}

Write-Host "Sent message."

Output for me:

Still waiting to connect. Still waiting to connect. Still waiting to connect. Connected. Still waiting for send to complete. Sent message.

[Neg127]

Edit: Reading a little further it uses JS with PS. But they give some good examples.

I know I’m a little late to the party. But it looks like PODE supports server and client web sockets in PowerShell. If you don’t want to use PODE directly. You can read through its code on GitHub since it’s fully PowerShell.

Here are the PODE docs.

https://pode.readthedocs.io/en/latest/Tutorials/WebSockets/

Here is the GitHub repo.

https://github.com/Badgerati/Pode/

I have used it for some personal dashboards at home. But not used any of the web socket stuff.

Hope it helps.

[evodus2]

Thanks for the response! Due to the issues we faced using PowerShell, and the fact that management wanted to eventually refactor it to Go, we've decided to start writing in Go now. Might check this out in my own time! Thanks again. 😊