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Joe, Jack and Jill use IM as a communication medium among themselves in Company A, where they work, and with customers and partners around the world. No goofing off here -- it's a legitimate work tool.

+-----+                               |Mary |
|Joe  |--------+                      +-----+
+-----+        |                        /
            +------+       ____________/
+-----+     |      |      /            \
|Jack |-----|Server|-----| The Internet |
+-----+     |      |      \____________/
            +------+                   \
+-----+        |                        \
|Jill |--------+                      +-----+
+-----+                               |Paul |

I'd like if, when the Internet connection dies, Joe, Jack and Jill are still able to IM each other within the company. After all, network connectivity between them hasn't been compromised. Can any of the popular IM networks do this transparently? Perhaps installing a proxy-like program in a company server?

These three
still see
each other
v v v v v v
+-----+                                 |Mary |
|Joe  |--------+                        +-----+
+-----+        |                          /
            +------+         ____________/
+-----+     |      |   D    /            \
|Jack |-----|Server|-/ E /-| The Internet |
+-----+     |      |   A    \____________/
            +------+   D                 \
+-----+        |                          \
|Jill |--------+                        +-----+
+-----+                                 |Paul |
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migrated from Jan 28 '10 at 11:10

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Excellent question! – Troggy Jan 27 '10 at 15:47
+1 for an actual, properly formatted ascii drawing – squillman Jan 27 '10 at 15:56
+1, for same reason as squillman, did you hand draw them or is there an application? It is brilliant! – William Hilsum Jan 27 '10 at 16:22
@Wil - By hand. I liked playing with Lego-like toys a lot when I was a kid. :) – JCCyC Jan 27 '10 at 16:31
reminds me of Nethack ... :-) – Rook Jan 28 '10 at 1:05
up vote 8 down vote accepted

As Iain, answered you can install an XMPP (also known as Jabber) server at your local network and have your workers use that server. There are many server implementations out there, both proprietary and open source.

Then you may have your XMPP server communicate with other XMPP servers (,, so that will be able to talk to or without them needing to subscribe to the sabe IM service.

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Yes, but not with public instant messengers.

Microsoft Communication Server can do this, so everyone locally can talk, but also integrate with third party IM providers such as AIM, MSN and Yahoo. (But it isn't cheap, or very easy to use in small environments. If you have thousands of users, it works VERY well!)

After this, you may want to take a look at a XMPP servers that you can run locally, however integration to third party products really depends on both the client and server you use.

I personally recommend you run a XMPP server on the server, and use a client such as Pidgin that will allow Joe, Jack and Jill to communicate locally, but also use whatever other networks they like. This will mean that they can talk on all networks and still communicate when the internet goes down.

(FYI, Jabberd is the one I used to use, however it has been years since I have done this and have no idea if anything better now exists)

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I would suggest taking a look at Prosody and Openfire as well as Jabberd. Openfire has a nice admin interface, Prosody very streamlined and lower system needs. – Scott Markwell Jan 27 '10 at 17:01
Excellent answer to an excellent question, gets my +1. – John T Jan 28 '10 at 6:23
+1 That's a great answer - use one IM product for internal system, and use a client that allows access to multiple IM systems. That gives you your redundancy and doesn't rely on your customers using a particular IM network. Pidgen will hook into XMMP locally, then all the major IM networks apart from Skype. – dunxd Jan 28 '10 at 11:21
We are doing the same thing with Openfire and their public transports to AIM/Yahoo/Gtalk. The other benefit of a solution like this from a corporate standpoint is that you can get central logging of all IM traffic. – Alex Jan 28 '10 at 15:22

Install a corporate XMPP (Jabber) server.

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Well, I'm probably also going to say jabber/XMPP- Run a server within your office lan, and turn on federation. I'm going to go a step further and suggest setting up gateways as well - so that your users can connect to MSN, yahoo and others - which should probably cover most of your bases

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