Having an Internet Service Bus up in the cloud is not very entertaining unless there are services in the bus. Therefore, I built one (and already showed some of the code basics) that’s hopefully fun to play with and will soon share the first version with you after some scrubbing and pending a few updates to the ISB that will optimize the authentication process. It’s a 0.1 version and an experiment. The code download should be ready in the next two weeks, including those adjustments. But you can actually play with parts of it today without compiling or installing anything. The info is at the bottom of this post.
To make matters really interesting, this sample not only shows how to plug a service into the cloud and call it from some Console app, but is a combo of two rather unusual hosts for WCF services: A Windows Live Messenger Add-In that acts as the server, and a Windows Vista Sidebar gadget that acts as the client.
Since the Silicon Valley scene is currently all over Twitter and clones of Twitter are apparently popping up somewhere every day, I thought I could easily provide fodder to the proponents of the alleged Microsoft tradition of purely relying on copying other’s ideas and clone them as well ;-) Well, no, maybe not. This is a bit different.
TweetieBot is an example of a simple personal service. If you choose to host it, you own it, you run it, you control it. The data is held nowhere but on your personal machine and it’s using the BizTalk Services ISB to stick its head up into the cloud and at a stable endpoint so that its easily reachable for a circle of friends, bridging the common obstacles of dynamic IPs, firewalls and NAT. No need to use UPnP or open up ports on your router. If you choose to do so, you can encrypt traffic so that there’s no chance that anyone looking at our ISB nor anyone else can see the what’s actually going across the wire.
Right now, lots of the Web 2.0 world lives on the assumption that everything needs to live at central places and that community forms around ad-driven hubs. The mainframe folks had a similar stance in the 70s and 80s and then Personal Computers came along. The pendulum is always swinging and I have little doubt that it will swing back to “personal” once more and that the federation of personal services will seriously challenge the hub model once more.
So what does the sample do? As indicated, TweetieBot is a bot that plugs into a Windows Live Messenger using a simple Add-In. Bart De Smet has a brilliant summary for how to build such Add-Ins. When the Add-In is active and someone chats the bot, it answers politely and remembers the chat line, time and sender. The bird has a leaky long term memory, though. It forgets everything past the last 40 lines.
Where it gets interesting is that the Add-In can stick three endpoints into the BizTalk Services ISB:
- A Request/Response Web Service that allows retrieving the list of the last 40 (or less) “tweets” and also allows client to submit tweets programmatically.
- An RSS service that allows (right now) anyone to peek in to the chat log of the last 40 tweets.
- An Event service that allows subscribers to get real-time notifications whenever a new tweet is recorded.
The accompanying Sidebar Gadget, which is implemented using WPF, is a client for two of these services.
When you drop the Gadget on the Sidebar, it will prompt for the IM address of the TweetieBot service you’d like to subscribe to. Once you’ve authenticated at the relay using your registered Information Card, the gadget will pull and show the current list of Tweets and subscribe to the Events service for real-time updates. And whenever someone chats the bot, the Sidebar gadget will immediately show the new entry. So even though the Gadget lives on some client machine that’s hidden between several layers of firewalls and behind NAT, it can actually get push-style event notifications through the cloud!
“How do I send events to clients?” must be one of the most frequent questions that I’ve been asked about Web Services in the past several years. Well, this is your answer right here.
While I’m still toying around with the code and the guys on the 1st floor in my building are doing some tweaks on the ISB infrastructure to make multi-endpoint authentication simpler, you can already play with the bot and help me a bit:
Using Windows Live Messenger you can chat (click here) email@example.com now. Drop a few lines. If the bot is online (which means that I’m not tinkering with it) it will reply. Then look at this RSS feed  and you can see what you and everyone else have been telling the bot recently. Enjoy.