[ns] can't get proc {} done to work

[Lars Eggert]

Hi,

after a few years of little ns use, I've recently started to use it  
more actively again. I remember being able to attach a proc {} done  
method to TCP Agents that fired when the connection closes, but  
either I'm remembering incorrectly how to do it, or stuff has changed  
since then.

Here's a snippet:

	set sender [new Agent/TCP/Sack1]
	set receiver [new Agent/TCPSink/Sack1]
	
	$ns attach-agent $src $sender
	$ns attach-agent $sink $receiver
	$ns connect $sender $receiver
	
	set ftp [new Application/FTP]
	$ftp attach-agent $sender
	$ns at 0 "$ftp produce 10"
	
	$sender proc {} done { puts "done"; }

I'd expect this to print "done" at some point, but it doesn't. Can  
anyone clue me in?

Thanks,
Lars