Eventmachine talk - Jan 2008 - Ping Pong server was( Problems trying to

> Tim, are you able to use an earlier EM version that is precompiled for
Win32
> (I think 0.8.0 is available)? At least that way you can get started with
> your application.
>
> I think that as a general rule, the deployment model for Windows has to be
> with precompiled gems, because the build-chain problem is such a bear on
> Windows (requiring VC6; requiring a compiler in the first place; etc, etc).
>

Yes the earlier version worked .8.1.  I''ll stick with this till I hear
otherwise from you guys.

Can I piggy back a quick question?

I want to write a program that sends packets back and forth between
two servers. One server sends a UDP message to the other, the other
replies back. At the same time the reverse is true. Both machines are
reacting to and initiating packets to each other.

Should I write a separate server and a sender or is it possible to
combine the two in the same program.

On Jan 3, 2008 10:24 PM, Tim Uckun <timuckun at gmail.com> wrote:
>  Yes the earlier version worked .8.1.  I''ll stick with this till I
hear
> otherwise from you guys.
>
Like all EM releases, 8.1 is perfectly stable and production-ready. You can
check the ChangeLog file in the distro to see what features have been added
since then.
>
> Can I piggy back a quick question?
>
> I want to write a program that sends packets back and forth between
> two servers. One server sends a UDP message to the other, the other
> replies back. At the same time the reverse is true. Both machines are
> reacting to and initiating packets to each other.
>
> Should I write a separate server and a sender or is it possible to
> combine the two in the same program.
>

Use the same program. In case you''re not already a UDP expert, read the
rdocs for EM#send_datagram, for important information that may save you some
trouble.

Specifically, if you want to use the often-seen firewall-friendly model in
which a UDP "server" receives packets on a well-known port, and sends
replies to the same port on the client machine (as NTP does, for example),
that model works perfectly well in EM. Just bind both sides to the same port
and use #send_data inside your #receive_data handler.
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> Use the same program. In case you''re not already a UDP expert,
read the
> rdocs for EM#send_datagram, for important information that may save you
some
> trouble.
>
> Specifically, if you want to use the often-seen firewall-friendly model in
> which a UDP "server" receives packets on a well-known port, and
sends
> replies to the same port on the client machine (as NTP does, for example),
> that model works perfectly well in EM. Just bind both sides to the same
port
> and use #send_data inside your #receive_data handler.
Question: so would that be two ports total, in that case?  one
send->recv, one send->recv (different ports)?

--
-Roger Pack
For God hath not given us the spirit of fear; but of power, and of
love, and of a sound mind" -- 2 Timothy 1:7

On Jan 4, 2008 10:37 AM, Roger Pack <rogerpack2005 at gmail.com>
wrote:
> > Use the same program. In case you''re not already a UDP
expert, read the
> > rdocs for EM#send_datagram, for important information that may save
you some
> > trouble.
> >
> > Specifically, if you want to use the often-seen firewall-friendly
model in
> > which a UDP "server" receives packets on a well-known port,
and sends
> > replies to the same port on the client machine (as NTP does, for
example),
> > that model works perfectly well in EM. Just bind both sides to the
same port
> > and use #send_data inside your #receive_data handler.
>
> Question: so would that be two ports total, in that case?  one
> send->recv, one send->recv (different ports)?
The two listening sockets must be bound either to different ports or
different interfaces.  Most UNIX-like OSes will allow you to create >
1 loopback interface or IP alias (in the case of a non-loopback).

Best regards,

--Michael

On Jan 4, 2008 1:37 PM, Roger Pack <rogerpack2005 at gmail.com> wrote:
> > Use the same program. In case you''re not already a UDP
expert, read the
> > rdocs for EM#send_datagram, for important information that may save
you
> some
> > trouble.
> >
> > Specifically, if you want to use the often-seen firewall-friendly
model
> in
> > which a UDP "server" receives packets on a well-known port,
and sends
> > replies to the same port on the client machine (as NTP does, for
> example),
> > that model works perfectly well in EM. Just bind both sides to the
same
> port
> > and use #send_data inside your #receive_data handler.
>
> Question: so would that be two ports total, in that case?  one
> send->recv, one send->recv (different ports)?
>
>

As I read the original use case, the idea was to have this ping-ponging
happening between two DIFFERENT COMPUTERS. Maybe I misread it.

If I''m correct, then you can use the identical software, with identical
ports, on both computers. Because of the UDP works, it''s entirely
possible
to send data from a UDP port that is listening (acting as a server), and
have the remote peer see the well-known port as the source address. EM wraps
all this stuff up quite nicely.

Read the rdoc for EM#send_datagram for more info.

In my experience, people have a lot more trouble grokking UDP than TCP, even
though it''s a much simpler protocol :-)
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> As I read the original use case, the idea was to have this ping-ponging
> happening between two DIFFERENT COMPUTERS. Maybe I misread it.
>
Yes that''s my intent but I might use the same machine for testing.


> Read the rdoc for EM#send_datagram for more info.
I don''t intend to write a line of code till I read all the rdocs and
even the comments in the source (which are very useful by the way,
thank you!)
>
> In my experience, people have a lot more trouble grokking UDP than TCP,
even
> though it''s a much simpler protocol :-)
>
I know a little. I would not call myself an expert by any means
though. I am just writing a tool to diagnose some network problems.

On Jan 5, 2008 3:37 AM, Tim Uckun <timuckun at gmail.com> wrote:
> > As I read the original use case, the idea was to have this
ping-ponging
> > happening between two DIFFERENT COMPUTERS. Maybe I misread it.
> >
>
> Yes that''s my intent but I might use the same machine for testing.
>
>
>
In that case, just parameterize it with two different ports (port A and port
B, since both peers combine the role of client and server) and you can run
two instances of the same code (with different parameters) on the same
machine.
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>
> In that case, just parameterize it with two different ports (port A and
port
> B, since both peers combine the role of client and server) and you can run
> two instances of the same code (with different parameters) on the same
> machine.

would it work to put them on different IP addresses? For example put
one at 127.0.0.100 and the other at 127.0.0.200?

On Jan 5, 2008 11:25 PM, Tim Uckun <timuckun at gmail.com> wrote:
> >
> > In that case, just parameterize it with two different ports (port A
and
> port
> > B, since both peers combine the role of client and server) and you can
> run
> > two instances of the same code (with different parameters) on the same
> > machine.
>
>
> would it work to put them on different IP addresses? For example put
> one at 127.0.0.100 and the other at 127.0.0.200?
>
>
I''d try it with different ports first.
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