Send files over PSSession

If it was a small file, you could send the contents of the file and the filename as parameters.

$f="the filename"
$c=Get-Content $f
invoke-command -session $s -script {param($filename,$contents) `
     set-content -path $filename -value $contents} -argumentlist $f,$c

If the file is too long to fit in whatever the limits for the session are, you could read the file in as chunks, and use a similar technique to append them together in the target location

---

PowerShell 5+ has built-in support for doing this, described in David's answer.

This is now possible in PowerShell / WMF 5.0

Copy-Item has -FromSession and -toSession parameters. You can use one of these and pass in a session variable.

eg.

$cs = New-PSSession -ComputerName 169.254.44.14 -Credential (Get-Credential) -Name SQL
Copy-Item Northwind.* -Destination "C:\Program Files\Microsoft SQL Server\MSSQL10_50.SQL2008R2\MSSQL\DATA\" -ToSession $cs

See more examples at here, or you can checkout the official documentation.

I faced the same problem a while ago and put together a proof-of-concept for sending files over a PS Remoting session. You'll find the script here:

https://gist.github.com/791112

#requires -version 2.0

[CmdletBinding()]
param (
    [Parameter(Mandatory=$true)]
    [string]
    $ComputerName,

    [Parameter(Mandatory=$true)]
    [string]
    $Path,

    [Parameter(Mandatory=$true)]
    [string]
    $Destination,

    [int]
    $TransferChunkSize = 0x10000
)

function Initialize-TempScript ($Path) {
    "<# DATA" | Set-Content -Path $Path 
}

function Complete-Chunk () {
@"
DATA #>
`$TransferPath = `$Env:TEMP | Join-Path -ChildPath '$TransferId'
`$InData = `$false
`$WriteStream = [IO.File]::OpenWrite(`$TransferPath)
try {
    `$WriteStream.Seek(0, 'End') | Out-Null
    `$MyInvocation.MyCommand.Definition -split "``n" | ForEach-Object {
        if (`$InData) {
            `$InData = -not `$_.StartsWith('DATA #>')
            if (`$InData) {
                `$WriteBuffer = [Convert]::FromBase64String(`$_)
                `$WriteStream.Write(`$WriteBuffer, 0, `$WriteBuffer.Length)
            }
        } else {
            `$InData = `$_.StartsWith('<# DATA')
        }
    }
} finally {
    `$WriteStream.Close()
}
"@
}

function Complete-FinalChunk ($Destination) {
@"
`$TransferPath | Move-Item -Destination '$Destination' -Force
"@
}

$ErrorActionPreference = 'Stop'
Set-StrictMode -Version Latest

$EncodingChunkSize = 57 * 100
if ($EncodingChunkSize % 57 -ne 0) {
    throw "EncodingChunkSize must be a multiple of 57"
}

$TransferId = [Guid]::NewGuid().ToString()


$Path = ($Path | Resolve-Path).ProviderPath
$ReadBuffer = New-Object -TypeName byte[] -ArgumentList $EncodingChunkSize

$TempPath = ([IO.Path]::GetTempFileName() | % { $_ | Move-Item -Destination "$_.ps1" -PassThru}).FullName
$Session = New-PSSession -ComputerName $ComputerName
$ReadStream = [IO.File]::OpenRead($Path)

$ChunkCount = 0
Initialize-TempScript -Path $TempPath 

try {
    do {
        $ReadCount = $ReadStream.Read($ReadBuffer, 0, $EncodingChunkSize)
        if ($ReadCount -gt 0) {
            [Convert]::ToBase64String($ReadBuffer, 0, $ReadCount, 'InsertLineBreaks') |
                Add-Content -Path $TempPath
        }
        $ChunkCount += $ReadCount
        if ($ChunkCount -ge $TransferChunkSize -or $ReadCount -eq 0) {
            # send
            Write-Verbose "Sending chunk $TransferIndex"
            Complete-Chunk | Add-Content -Path $TempPath
            if ($ReadCount -eq 0) {
                Complete-FinalChunk -Destination $Destination | Add-Content -Path $TempPath
                Write-Verbose "Sending final chunk"
            }
            Invoke-Command -Session $Session -FilePath $TempPath 

            # reset
            $ChunkCount = 0
            Initialize-TempScript -Path $TempPath 
        }
    } while ($ReadCount -gt 0)
} finally {
    if ($ReadStream) { $ReadStream.Close() }
    $Session | Remove-PSSession
    $TempPath | Remove-Item
}

Some minor changes would allow it to accept a session as a parameter instead of it starting a new one. I found the memory consumption on the Remoting service on the destination computer could grow quite large when transferring large files. I suspect PS Remoting wasn't really designed to be used this way.