c# - Is there a way to enable the SO_REUSEADDR socket option when using System.Net.HttpListener?

Question

Been searching for this for over an hour now, and I have not found in documentation nor in examples on the web how to enable the SO_REUSEADDR option when working with the HttpListener class.

My specific use case is within a Powershell script, but even if there is an answer in C#, that would be fine. This is about as cut-and-dry as it gets:

$Listener = New-Object System.Net.HttpListener
$Listener.Prefixes.Add('http://+:9999/')
Try
{
    $Listener.Start()
    # While loop here to handle requests; omitted for brevity
}
Catch
{
    # omitted here for brevity
}

There are times where I Ctrl-C to break out of the script while testing, and leaving the loop this way does not allow $Listener.Stop() to be called and the socket properly closed. (Yes, I know - don't do this if it breaks things)

Normally, when I need a listening socket, I make use of SO_REUSEADDR to handle those times where things don't clean up properly to allow me to restart my listener without having to wait 30 minutes for the port to be available again. Is there a way to do this with HttpListener and I'm just missing it?

Answer 1

No, you can't use SO_REUSEADDR with HttpListener.

The reason is that the HttpListener doesn't actually manage the underlying socket - it simply registers application-level prefixes with the HTTP.sys driver, who in turn manages the underlying connection.

To use SO_REUSEADDR, you could create a TcpListener and set the socket option on the underlying socket (accessible through the Server property) with SetSocketOption():

$TcpListener = New-Object System.Net.Sockets.TcpListener 9999
$TcpListener.Server.SetSocketOption("Socket", "ReuseAddress", 1)
$TcpListener.Start()

But now you have to implement all the convenient things that HttpListener provides on you own (header parsing, content validation etc.).

---

That being said, this may solve the practical issue you face:

try{
    $Listener.Start()
}
catch{
}
finally{
    $Listener.Stop()
    $Listener.Dispose()
}

(don't paste this into you prompt/ISE, you need to save this to a script, or enclose in a script block for finally to be evaluated properly on interruption)