From: why@...
Date: 2002-06-22T02:48:05+09:00
Subject: Re: detecting a socket dropping in multi-threaded app

Firestone, Mark - Technical Support (mark.firestone@gossgraphic.co.uk) wrote:
> I'm still working on my Ruby BBS project.  I need to be able to run some
> code when a user drops offline without logging off.  Right now, Ruby is just
> killing the thread.  I need to know how to make it pass an exception (or
> something) back to the main loop so the main loop can take the user out of
> the online user database.  I've tried testing for nil and raising an
> exception, but it doesn't seem to work.  Help please!! You guys never let me
> down.
> 
> thanks in advance!
> 
> Mark

First, I don't see any begin..rescue around your TCPSocket#each_byte:

  begin
    @sock.each_byte do |fred|
      # Process bytes sent     
    end
  rescue
    # Handle exception here..
  end

I find the surest way of finding a disconnect is to implement a simple PING request from the server to the client.  It looks like your byte commands could include a PING response from the client.  I just run a separate thread that periodically checks that the PING count is climbing..  Then, set Thread#abort_on_exception = false so you can make sure that only clients that don't return pings get killed.  If you go this route, then don't forget to use a mutex.

-- 

Jonathan Gillette
iNetZ Media