Druby using just IP addresses

ruby-talk
1

Hi

I'd like to use druby, but with the client using just an IP address to contact the server, and vice versa. The initial connection works fine, but then it seems the server can't find the client to send a reply when a method is invoked.

I realise this question has been asked before, and answered by 'fix your DNS' or 'tweak etc/hosts'.

However, this is for an end-user app, so most users (of clients and servers) won't be permitted to access etc/hosts, even if I wanted to explain what they should do to it.

So
- has anyone hacked drb to work without hostnames?
- failing that, is there a deep technical reason that using IP addresses only will never work and I shouldn't bother even trying? It seems lots of other net applications work fine without caring that DNS is fixed, but I've not got masses of experience with socket programming in Ruby.

thanks
alex

2

Alex Fenton wrote:

Hi
I'd like to use druby, but with the client using just an IP address to contact the server, and vice versa. The initial connection works fine, but then it seems the server can't find the client to send a reply when a method is invoked.

I realise this question has been asked before, and answered by 'fix your DNS' or 'tweak etc/hosts'.
However, this is for an end-user app, so most users (of clients and servers) won't be permitted to access etc/hosts, even if I wanted to explain what they should do to it.

So
- has anyone hacked drb to work without hostnames?
- failing that, is there a deep technical reason that using IP addresses only will never work and I shouldn't bother even trying? It seems lots of other net applications work fine without caring that DNS is fixed, but I've not got masses of experience with socket programming in Ruby.

Probably someone has suggested this before, but have you tried

Socket.do_not_reverse_lookup = true

?

···

--
       vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407

3

Hi

I'd like to use druby, but with the client using just an IP address to contact the server, and vice versa. The initial connection works fine, but then it seems the server can't find the client to send a reply when a method is invoked.

I realise this question has been asked before, and answered by 'fix your DNS' or 'tweak etc/hosts'.

However, this is for an end-user app, so most users (of clients and servers) won't be permitted to access etc/hosts, even if I wanted to explain what they should do to it.

So
- has anyone hacked drb to work without hostnames?
- failing that, is there a deep technical reason that using IP addresses only will never work and I shouldn't bother even trying? It seems lots of other net applications work fine without caring that DNS is fixed, but I've not got masses of experience with socket programming in Ruby.

I'm not sure what isn't working for you with out some code. I do have
an idea though this seems to work for me:

# Server's irb session:

require 'drb'

=> true

DRb.start_service('druby://192.168.0.104:1234', "abc")

=> #<DRb::DRbServer ....>

# Client's session:

require 'drb'

=> true

DRb.start_service('druby://192.168.0.101:1234')

=> DRb::DRbServer ....>

remote = DRbObject.new(nil, 'druby://192.168.0.104:1234')

=> #<DRb::DRbObject ....>

remote.to_s # Force display

=> "abc"

remote.size

=> 3

remote.replace("ruby")

=> #<DRb::DRbObject ....>

remote.to_s

=> "ruby"

remote.size

=> 4

Note that it is a good idea to specify an explicit interface on the
client side so you make sure it binds to something the server can
reach. Some systems will bind to something like 127.0.0.1 when
resolving the host's name (i.e. Ubuntu does this). The two way channel
is vital to have DRb work reliably in most cases (unmarshalled objects
can be referenced in both directions).

Brian.

···

On 10/4/06, Alex Fenton <alex@deleteme.pressure.to> wrote:

4

I'd like to use druby, but with the client using just an IP address to contact the server, and vice versa. The initial connection works fine, but then it seems the server can't find the client to send a reply when a method is invoked.

I realise this question has been asked before, and answered by 'fix your DNS' or 'tweak etc/hosts'.
However, this is for an end-user app, so most users (of clients and servers) won't be permitted to access etc/hosts, even if I wanted to explain what they should do to it.

So
- has anyone hacked drb to work without hostnames?

DRb uses Socket.gethostname to determine the hostname. If you don't otherwise use this method just override it to return an IP address.

- failing that, is there a deep technical reason that using IP addresses only will never work and I shouldn't bother even trying? It seems lots of other net applications work fine without caring that DNS is fixed, but I've not got masses of experience with socket programming in Ruby.

Most programs aren't servers that are running on arbitrary machines having other arbitrary machines connecting back to them.

One solution would be adding socket multiplexing in place of launching servers.

···

On Oct 4, 2006, at 10:50 AM, Alex Fenton wrote:

--
Eric Hodel - drbrain@segment7.net - http://blog.segment7.net
This implementation is HODEL-HASH-9600 compliant

http://trackmap.robotcoop.com

5

Brian Mitchell wrote:

Hi

I'd like to use druby, but with the client using just an IP address to contact the server, and vice versa. The initial connection works fine, but then it seems the server can't find the client to send a reply when a method is invoked.

I realise this question has been asked before, and answered by 'fix your DNS' or 'tweak etc/hosts'.

However, this is for an end-user app, so most users (of clients and servers) won't be permitted to access etc/hosts, even if I wanted to explain what they should do to it.

So
- has anyone hacked drb to work without hostnames?
- failing that, is there a deep technical reason that using IP addresses only will never work and I shouldn't bother even trying? It seems lots of other net applications work fine without caring that DNS is fixed, but I've not got masses of experience with socket programming in Ruby.

Note that it is a good idea to specify an explicit interface on the
client side so you make sure it binds to something the server can
reach. Some systems will bind to something like 127.0.0.1 when
resolving the host's name (i.e. Ubuntu does this). The two way channel
is vital to have DRb work reliably in most cases (unmarshalled objects
can be referenced in both directions).

Adding to that: it might well be that you are trying to do things in environments that simply won't permit this. If your client is behind a firewall / router with NAT and the server tries to open a connection to the client system that's often not permitted. So, in order to get this to work in these environments someone must actually change FW config.

Kind regards

  robert

···

On 10/4/06, Alex Fenton <alex@deleteme.pressure.to> wrote:

6

Brian Mitchell wrote:

···

On 10/4/06, Alex Fenton <alex@deleteme.pressure.to> wrote:

Hi

I'd like to use druby, but with the client using just an IP address to contact the server, and vice versa

Note that it is a good idea to specify an explicit interface on the
client side so you make sure it binds to something the server can
reach. Some systems will bind to something like 127.0.0.1 when
resolving the host's name (i.e. Ubuntu does this).

Thank you, that was it. Added an explicit IP address on the client side made it work fine.

I was using start_service on the client with no args. It was binding to the windows machine name, and the OS X server I was trying to connect to couldn't resolve it back.

alex