Trying to use WakeOnLan and keep getting errors

PowerShell Help
1

CoPilot was not helpful in trying to get WakeOnLan to function. Nothing seems to work. Does WakeOnLan command ever work. Using PowerShell 7.

I get these types of errors:
PS C:\Users\gharouff_dadmin.METROHEALTH> import-module wakeonlan

PS C:\Users\gharouff_dadmin.METROHEALTH> Invoke-wakeonlan -MacAddress 40:1c:83:40:ad:3f

InvalidArgument: Cannot convert value “0x40:1c:83:40:ad:3f” to type “System.Byte”. Error: "Additional non-parsable characters are at the

end of the string."

I used “-” instead of “:” and get the same error

Imported and installed WakeOnLan modules installed ok
Used Get-Command -Module WakeOnLan – returned command type – Function, Name – Invoke-WakeOnLan, version 1.0, source wakeonlan

2

I cannot reproduce. I recommend you type the mac instead of copy/pasting, it’s likely there are additional characters you can’t see.

3

Hello and welcome to the forum.
Whenever you’re sharing code please make sure to use the Preformatted text button. It’s often behind the gear icon.

The first thing I did was look up the module you’re using. WakeOnLane was published to the PowerShell Gallery in 2015 and written with Powershell v2 as a minimum. Just things to keep in mind.

InvalidArgument: Cannot convert value "0x40:1c:83:40:ad:3f" to type "System.Byte"

Your MAC address suddenly has a 0x40 at the beginning of it instead of your original “40”.
The param block from the source code takes your input in as a string:

Param (
    [Parameter(ValueFromPipeline)]
    [String[]]$MacAddress
)

And later converts it to bytes:

$Mac = $MacString.Split('-:') | Foreach {[Byte]"0x$_"}

 # WOL Packet is a byte array with the first six bytes 0xFF, followed by 16 copies of the MAC address

$Packet = [Byte[]](,0xFF * 6) + ($Mac * 16)

When I run just the relevant code in Windows Powershell v5.1 it works.
When I run it in Powershell 7.5 it fails with the error:

InvalidArgument: Cannot convert value "0x40:1c:83:40:ad:3f" to type "System.Byte". Error: "Additional non-parsable characters are at the end of the string."

I don’t know which part of this syntax it doesn’t like:

$Mac = $MacString.Split('-:') | Foreach {[Byte]"0x$_"}

But that’s your problem.

Seeing your PS prompt in your posted text we can see you’re on a Windows machine. I would advise using Windows Powershell to use this module instead.
I would also advise you edit your post and remove your username from your prompt as it reveals potentially sensitive information about your organization.

EDIT: got it. The author used the Split() method of a String object and included two characters to potentially split on: -, ;
In Windows Powershell v5.1, and .NET framework 4.5 that works:

# v5.1
PS> $MacString = "40:1c:83:40:ad:3f"
PS> $MacString.Split('-:')   
40
1c
83
40
ad
3f

But in PS v7.5 it doesn’t split at all:

# v7.5
PS> $MacString = "40:1c:83:40:ad:3f"
PS> $MacString.Split('-:')  
40:1c:83:40:ad:3f

The definition on [Microsoft’s docs]( String.Split Method (System) | Microsoft Learn) for both version of .NET says that Split will accept an array of characters as delimiters. But simply passing '-:' isn’t strictly an array, but somehow this worked in older versions of Powershell.
I was able to make it work in both versions by literally creating a character array.

$MacString = "40:1c:83:40:ad:3f"
[Char[]]$Chars = [Char]'-',[Char]':'
$MacString.Split($Chars)# | Foreach {[Byte]"0x$_"}

@LearnLaughOps solution of switching to the -Split operator with Regex pattern of This|That is what I would do.
You can edit your local copy of the module manually yourself, open an issue on github, or fork the project for yourself.

1 Like
4

To resolve this I think you can just edit the module and update the following line:
$Mac = $MacString.Split('-:') | Foreach {[Byte]"0x$_"}

Updated to:
$Mac = $MacString -split '-|:' | Foreach {[Byte]"0x$_"}

I can’t figure out what changed from version 5-7.

1 Like
5

Looks like a known problem. There is a fix, but the PR hasn’t been completed so there’s no updated version on the gallery.

Might be worth trying this branch of the fork from the author of the fix:

2 Likes
6

I see, I didn’t try it in powershell core, so that’s my mistake! OP you could use my function if you like, it works in 7.x as well

4 Likes
7

awesome @krzydoug I was just scaffolding out a new module project based on this conversation. Hope you don’t mind if I borrow some of your code.

8

Not at all. This is my number 1 visited script and most those visiting come from Reddit. At least you asked :stuck_out_tongue:

2 Likes
9

I spent longer on it than I intended but my first draft of a Wake-on-LAN module that’s compatible with Desktop and Core editions as well as cross platform is up.
PSWoL

1 Like