readme

java开源的企业总线.xmlBlaster

#
# xmlBlaster/demo/javaclients/cluster/firewall/README
# [e-mail] 2003/12/06
#

Example of a slave xmlBlaster cluster node 'frodo' running behind
a firewall which allows outbound socket connection only.

On the outside we have a master xmlBlaster cluster node 'heron':


 clientA -+                                          +- clientX
          |                                          |
  ...     +-> frodo ---SOCKET---|firewall|--> heron -+- ...
          |                                          |
 clientN -+                                          +- clientY


We have configured frodo to use the SOCKET protocl to connect
to heron. This allows to tunnel back update() messages using
the same outbound socket connection.
It is important that we configure heron to be the master of all
messages (see frodo.properties).

Note that heron does NOT connect to frodo (the firewall would
not allow it).

Current drawback: frodo can't be master of some message topics
as heron would in this case try to establish a connection,
this issue would need some coding in xmlBlaster (if heron is
connected by frodo already try to reuse the socket connection).

If the firewall only allows http with proxies inbetween this
setup won't help. You need to switch to email protocol or
reuse the applet code which can handle this.


Try the example:
================

First we do this on the same machine.
Open 5 xterm (or DOS boxes) and change to directory

  xmlBlaster/demo/javaclients/cluster/firewall

Start heron (the master):

  java org.xmlBlaster.Main -propertyFile heron.properties

  Note that heron is configured with xmlBlasterPluginsSimple.xml
  (see heron.properties) to be very simple to avoid too much
  logging output and to avoid port conflicts as we run on the
  same machine as frodo.
  
Start frodo (the slave): 

  java org.xmlBlaster.Main -propertyFile frodo.properties

  Note that frodo runs in default mode with all protocol drivers
  switched on. Look at the logging output and see how frodo
  connects to heron with the SOCKET protocol.

Start a publisher (which connects to frodo):

  java javaclients.HelloWorldPublish -numPublish 100 -oid ClusterTest -session.name publisherToFrodo/1

  This publisher connects to frodo and each time you press the enter key
  a message is published to frodo and forwarded to heron

Start a subscriber (which connects to frodo):

  java javaclients.HelloWorldSubscribe -oid ClusterTest

Start a subscriber (which connects to heron):

  java javaclients.HelloWorldSubscribe -oid ClusterTest -protocol SOCKET -dispatch/connection/plugin/socket/port 8900 -session.name subscriberAtHeron


Try the example behind a firewall:
==================================

You need to edit frodo.properties and replace the socket address
with the IP (or DNS hostname) where heron is running on,
for example change

   socket://:8900\
   
to

   socket://myServer.myCompany.com:8900\

and start the second subscriber with this address as well:

   java javaclients.HelloWorldSubscribe \
         -oid ClusterTest \
         -protocol SOCKET \
         -dispatch/connection/plugin/socket/hostname myServer.myCompany.com \
         -dispatch/connection/plugin/socket/port 8900 \
         -session.name subscriberAtHeron

Note that the only port which needs to be opened through the firewall
is the outgoing port 8900 to the server myServer.myCompany.com


Making it secure:
=================

If you want to secure the communication
just make a ssh connection from the frodo host
to the heron host and tunnel the SOCKET connection
through it.
In this case frodo connects to the local side of the
ssh tunnel and the remote ssh deamon forwards everything
to heron.