forcing userdata to be gc'd?

[John Dunn <John.Dunn@...>]

If I have a userdata that wraps a limited system resource ( ie file handle, socket, large block of C memory, etc ), is there a way to make the userdata more likely to be garbage collected? For example, if I have a userdata wrapped socket with the following code

sock = nil
for i = 1,1000 do
  sock = socket.new() -- create new userdata wrapping a socket
end

1000 sockets will likely be created before any of the non-referenced userdatas are collected. I can solve this with require careful script coding ( having a sock:close() call that has to be called when you are done with the socket, calling collectgarbage(), etc ) but I'd like a solution that is more robust than that. It seems like a way to tag something to always be garbage collected as soon as there are no longer any references might work.

John