Eventmachine talk - Jan 2008 - Having very odd problems with UDP.

I am using eventmachine 0.8.1 on windows XP and am having very odd problems.

This snippet of code gives the error that follows it.

class EchoServer
  def receive_data data
      puts data
      send_data ">>>you sent: #{data}"
      if data =~ /quit/i
         puts "quitting"
         close_connection
         EventMachine::stop_event_loop
      end
  end
end

EventMachine::run {
  EventMachine::open_datagram_socket "127.0.0.99", port, EchoServer
}

Gives the error

d:/ruby/lib/ruby/gems/1.8/gems/eventmachine-0.8.1-x86-mswin32/lib/eventmachine.rb:959:in
`event_callback'': EventMachine::ConnectionNotBound
(EventMachine::ConnectionNotBound)
        from
d:/ruby/lib/ruby/gems/1.8/gems/eventmachine-0.8.1-x86-mswin32/lib/eventmachine.rb:223:in
`release_machine''
        from
d:/ruby/lib/ruby/gems/1.8/gems/eventmachine-0.8.1-x86-mswin32/lib/eventmachine.rb:223:in
`run''
        from eventmachine_test.rb:26



This snippet of code kind of works..

module EchoServer
   def receive_data data
      puts data
      send_data ">>>you sent: #{data}"
      if data =~ /quit/i
         puts "quitting"
         close_connection
         EventMachine::stop_event_loop
      end
   end
end

EventMachine::run {
  EventMachine::open_datagram_socket "127.0.0.99", port, EchoServer
}


This works halfway and only once.

The first time I call it the puts statement works but the send_data
doesn''t. Any further calls don''t seem to do anything. The puts
doesn''t
work neither does the send_data.


Obviously I am missing something here.

The ConnectionNotBound error is really quite misleading. It is something
that needs to be changed because that''s the "catch-all"
exception. I''ve seen
in thrown when I had a NoMethodError in my code, and similar problems. So to
be sure, wrap your code in a begin ... rescue block and see what exactly is
being thrown.

As for your code, I do see something slightly wrong. You should use
close_connection_after_writing, because data is not sent immediately when
you call send_data, but is queued up to be sent when it''s most
efficient,
and after the received_data block is done.

Jason

On Jan 6, 2008 3:30 AM, Tim Uckun <timuckun at gmail.com> wrote:
> I am using eventmachine 0.8.1 on windows XP and am having very odd
> problems.
>
> This snippet of code gives the error that follows it.
>
> class EchoServer
>  def receive_data data
>      puts data
>      send_data ">>>you sent: #{data}"
>      if data =~ /quit/i
>         puts "quitting"
>         close_connection
>         EventMachine::stop_event_loop
>      end
>  end
> end
>
> EventMachine::run {
>  EventMachine::open_datagram_socket "127.0.0.99", port,
EchoServer
> }
>
> Gives the error
>
> d:/ruby/lib/ruby/gems/1.8/gems/eventmachine-0.8.1-x86-mswin32
> /lib/eventmachine.rb:959:in
> `event_callback'': EventMachine::ConnectionNotBound
> (EventMachine::ConnectionNotBound)
>        from d:/ruby/lib/ruby/gems/1.8/gems/eventmachine-0.8.1-x86-mswin32
> /lib/eventmachine.rb:223:in
> `release_machine''
>        from d:/ruby/lib/ruby/gems/1.8/gems/eventmachine-0.8.1-x86-mswin32
> /lib/eventmachine.rb:223:in
> `run''
>        from eventmachine_test.rb:26
>
>
>
> This snippet of code kind of works..
>
> module EchoServer
>   def receive_data data
>      puts data
>      send_data ">>>you sent: #{data}"
>      if data =~ /quit/i
>         puts "quitting"
>         close_connection
>         EventMachine::stop_event_loop
>      end
>   end
> end
>
> EventMachine::run {
>  EventMachine::open_datagram_socket "127.0.0.99", port,
EchoServer
> }
>
>
> This works halfway and only once.
>
> The first time I call it the puts statement works but the send_data
> doesn''t. Any further calls don''t seem to do anything. The
puts doesn''t
> work neither does the send_data.
>
>
> Obviously I am missing something here.
> _______________________________________________
> Eventmachine-talk mailing list
> Eventmachine-talk at rubyforge.org
> http://rubyforge.org/mailman/listinfo/eventmachine-talk
>
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On Jan 6, 2008 3:30 AM, Tim Uckun <timuckun at gmail.com> wrote:
> I am using eventmachine 0.8.1 on windows XP and am having very odd
> problems.
>
> This snippet of code gives the error that follows it.
>
> class EchoServer
>  def receive_data data
>      puts data
>      send_data ">>>you sent: #{data}"
>      if data =~ /quit/i
>         puts "quitting"
>         close_connection
>         EventMachine::stop_event_loop
>      end
>  end
> end
>
> EventMachine::run {
>  EventMachine::open_datagram_socket "127.0.0.99", port,
EchoServer
> }
>
> Gives the error
>
> d:/ruby/lib/ruby/gems/1.8/gems/eventmachine-0.8.1-x86-mswin32
> /lib/eventmachine.rb:959:in
> `event_callback'': EventMachine::ConnectionNotBound
> (EventMachine::ConnectionNotBound)
>        from d:/ruby/lib/ruby/gems/1.8/gems/eventmachine-0.8.1-x86-mswin32
> /lib/eventmachine.rb:223:in
> `release_machine''
>        from d:/ruby/lib/ruby/gems/1.8/gems/eventmachine-0.8.1-x86-mswin32
> /lib/eventmachine.rb:223:in
> `run''
>        from eventmachine_test.rb:26
>
>
>
> This snippet of code kind of works..
>
> module EchoServer
>   def receive_data data
>      puts data
>      send_data ">>>you sent: #{data}"
>      if data =~ /quit/i
>         puts "quitting"
>         close_connection
>         EventMachine::stop_event_loop
>      end
>   end
> end
>
> EventMachine::run {
>  EventMachine::open_datagram_socket "127.0.0.99", port,
EchoServer
> }
>
>
> This works halfway and only once.
>
> The first time I call it the puts statement works but the send_data
> doesn''t. Any further calls don''t seem to do anything. The
puts doesn''t
> work neither does the send_data.
>
>
> Obviously I am missing something here.
>

Jason is right, the ConnectionNotBound error is very misleading. What has
happened is that your Ruby code has thrown an exception, and the EM reactor
loop caught it and reported it as something different.

You can work around your problem by putting begin/rescue into your code to
find and fix the error.

Meanwhile we have to fix the reporting problem in EM. I''ve tried
several
different approaches to this, but they all had either performance problems
or were just as confusing, only different.
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> You can work around your problem by putting begin/rescue into your code to
> find and fix the error.
I have modified the code like this.

port = ARGV[1].to_i
ip = ARGV[0]

begin
   module EchoServer
     def receive_data data
          puts data
          send_data ">>>you sent: #{data}"
          close_connection
          if data =~ /quit/i
             close_connection
             EventMachine::stop_event_loop
          end
     end
   end

   EventMachine::run {
      EventMachine::open_datagram_socket  ip, port , EchoServer
      #EventMachine::start_server  ip, port , EchoServer
   }

rescue => e
  puts e.message
  EventMachine::stop_event_loop
end


I am using a program called  sockettest to conduct all my testing
http://sourceforge.net/projects/sockettest/

The results:

The rescue never gets triggered.

The start_server works exactly as you would expect. It listens and
responds correctly.

The open_datagram_socket never sends replies (or if it does then
sockettest is unable to display them)

If you use any IP in the 127.0.0.0/24 subnet open_datagram_socket only
works once (the first time). Any subsequent sends seem to vanish into
thin air. The puts never triggers.

If you use a normally bound IP address it gets to the puts every time
but as I said above it never seems to send anything back.

Very weird.

On Jan 6, 2008 8:13 PM, Tim Uckun <timuckun at gmail.com> wrote:
> > You can work around your problem by putting begin/rescue into your
code
> to
> > find and fix the error.
>
> I have modified the code like this.
>
> port = ARGV[1].to_i
> ip = ARGV[0]
>
> begin
>   module EchoServer
>     def receive_data data
>          puts data
>          send_data ">>>you sent: #{data}"
>          close_connection
>          if data =~ /quit/i
>             close_connection
>             EventMachine::stop_event_loop
>          end
>     end
>   end
>
>   EventMachine::run {
>      EventMachine::open_datagram_socket  ip, port , EchoServer
>      #EventMachine::start_server  ip, port , EchoServer
>   }
>
> rescue => e
>  puts e.message
>  EventMachine::stop_event_loop
> end
>
>
> I am using a program called  sockettest to conduct all my testing
> http://sourceforge.net/projects/sockettest/
>
> The results:
>
> The rescue never gets triggered.
>
> The start_server works exactly as you would expect. It listens and
> responds correctly.
>
> The open_datagram_socket never sends replies (or if it does then
> sockettest is unable to display them)
>
> If you use any IP in the 127.0.0.0/24 subnet open_datagram_socket only
> works once (the first time). Any subsequent sends seem to vanish into
> thin air. The puts never triggers.
>
> If you use a normally bound IP address it gets to the puts every time
> but as I said above it never seems to send anything back.
>
> Very weird.
> _______________________________________________
> Eventmachine-talk mailing list
> Eventmachine-talk at rubyforge.org
> http://rubyforge.org/mailman/listinfo/eventmachine-talk
>

The idea would be to wrap just the code that gets called:

  module EchoServer
    def receive_data data
         begin
           puts data
           send_data ">>>you sent: #{data}"
           close_connection
           if data =~ /quit/i
              close_connection
              EventMachine::stop_event_loop
           end
        rescue => ex
          # do stuff with exception here
        end
    end
  end

  EventMachine::run {
     EventMachine::open_datagram_socket  ip, port , EchoServer
     #EventMachine::start_server  ip, port , EchoServer
  }

Wrapping the whole bit isn''t going to do you any good. Outside of that
not
really making any sense, received_data is itself wrapped in a begin ...
rescue block, and *that* is where ConnectionNotBound is thrown.

Jason
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>
>  The idea would be to wrap just the code that gets called:

I tried that first. Since I was not catching exceptions I moved out to
the entire codebase just in case something was happening upstream.
>    }
> Wrapping the whole bit isn''t going to do you any good. Outside of
that not
> really making any sense, received_data is itself wrapped in a begin ...
> rescue block, and *that* is where ConnectionNotBound is thrown.
>

Maybe I should try on my mac or linux machines. The code definitely
has to work on windows so that''s why I am developing in windows.

In a nutshell.

If the UDP listener is listening on the 127 IPs it only accepts a
packet the first time. All subsequent packets seem to be ignored.
If it''s listening on "normal" IP addresses it receives all
packets.
send_data never works with UDP.

UDP is stateless so maybe send_data isn''t supposed to work unless I
set up a listener right?