I have an application, where I need to add role-based messaging. The messages are generated ny the application itself, and every message have an starttime (where is show on the client message-window) and an expire-time. Depending on your role, you will see a subset of the messages. Some messages are VERY important, and should be pushed to the client instantly (we are talking milli-seconds - not seconds). Also - when a user log in, he/she should be the current messages for his/her role.
Basically this is a blackboard, where the client see a view of the blackboard (depending on the role). It has to be really fast and reliable, as it will be used in an emergency centre handling calls for ambulances and fire)
Anyone know which technology I should use (application is written in .NET 2.0) or if a product exists, which I could use?
You may try using Retlang.
Sounds to me like this is a dream, role for Tibco RV / multicast, if your org has the dough for the license/backend...
If not, have a look at UDP multicast where you server would broadcast all blackboard events, and each client would filter what needs to be displayed.
Cheers,
Florian
You may try GigaSpaces http://www.gigaspaces.com they provide a pretty mature platform (you may say enterprise ready) for blackboard/messaging systems featuring support of Java and .NET and ability to deal with blackboards/queues/roles on a very fine grade granularity.
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I am building a social application and was wondering how facebook achieve their notifications.
As you know, facebooks notifications are instant. As soon as someone takes an action, people are notified.
I assume they don't have a query running on the database all the time.
Can someone point me in the right direction. Thanks
Since your question is tagged with C#, ASP.NET you should use the awesome SignalR library. Basically SignalR enables you to send push notifications to the clients. Which exact underlying technique it uses is influenced by the capabilities of the Server and the Client.
There is a big real time chat site called jabbR that is built on top of SignalR:
http://jabbr.net/
Here are some more links that should get you started.
Project site: http://signalr.net/
Hosted Code (Open Source): https://github.com/SignalR/SignalR
Wiki: https://github.com/SignalR/SignalR/wiki
Projects using it: https://github.com/SignalR/SignalR/wiki/Projects-Using-SignalR
Facebook uses a messaging protocol (which it designed) called Thrift. This allows notifications from clients to servers with very low latency. I would imagine updates on the server would be triggered depending on the user action and relevant users that are logged in would be notified by the same mechanism.
Using a messaging protocol such as thrift (also see Protocol buffers) clients don't have to poll the server for updates, instead the server can push notifications to clients. To do this the server needs to have a notion of who is logged in at any one time (Login, logout handshaking) and of them, who should receive notifications from a particular client action.
Easier said than done, especially when you have 800 million potential users logged in!
You might want to take a look at http://nodejs.org/ - it is an event-driven model which is perfectly ideal for a 'social network' / instant notifications scenario.
FYI: You also might find that using a non-SQL database such as MongoDB (http://www.mongodb.org/) will be a lot faster when querying from the DB since each 'person' object in a social network scenario has his/her own unique attributes - which in a normal SQL database is hard to design.
I am looking to build an online customer support system for one of our company sites and had a few queries with regards to the structuring.
The scenario is this. We would like users of our site to be able to click a "Live Chat Support" button, at which point they would get a popup that tries to connect them to one of our support team.
Our support team on the other hand, will be running desktop clients. Whenever a user on our site clicks the link, all of the desktop clients will "ring". Whenever a support team member "answers" the call, the other clients will stop ringing and that member will begin chatting with the web user.
Given that our desktop client will be made using WPF in C#.NET and our site is ASP.NET MVC 2 - what would be the best way to establish communication between the two?
My initial thoughts were to have the web side store the chat in an SQL database and somehow "Ping" the relevent desktop client telling it to update its chat log. Similarly for the desktop to the web. But I am unsure how to go about implement this between two different platforms. If it were desktop client to desktop client I imagine it would much easier, but this is not the case.
Also, please bare in mind that I realise there are already commercial applications out there that do this. However, we require some bespoke functionality that goes beyond a simple chat - it is not worth going into the specifics but basically we must implement our own solution.
Any help is much appreciated.
Web technology is an inappropriate platform for implementing real-time interaction. It can be done, of course, but you will certainly have issues with scalability, responsiveness and development effort. I urge you to examine your requirements very carefully and consider whether it is at all possible to leverage a vendor product to accomplish what you want to do.
If you still want to strike out on your own, the main hurdle you will have to overcome is how to push messages to the browser. "Pinging" the browser from the server is impossible using pure web technologies, because HTTP is built on a "pull-only" request/response model. There is no persistent connection maintained between the client in the server. After the server has finished sending the page to the broswer, the connection is gone.
You could poll the web server for new messages, but this is not a scalable solution. If you're only dealing with a very small (say single digits) number of users, then this might work, but your responsiveness will be limited by the speed at which you poll, and the faster you poll, the less scalable this solution will be.
A better solution would be to use Silverlight, Flash, or some other thick-client technology running in the browser. Then you could implement a service that handles message routing between clients. This article on CodeProject might be a good place to start.
I've inherited an ASP.NET website written in c# using an mssql 2k8 database that is sending emails based on an insert into a message table via a trigger using database mail :| One of any failures and too many things rollback, aren't logged and no email is sent...
What a mess. I've written a few email subsystems in the past and I thought I'd ask for input before starting a rewrite here. What are the best practices for queuing/sending email in a Microsoft environment? Should I be pushing emails to a queue, from there pulling, sending, logging? DB Email seems like a fail. Is the queue managed in SQL server? Does SQL Server call a C# app? If an email send fails, what's a good approach for recovery?
Thanks for any insight!
I think you are correct to completely separate the use of system functions: use SQL for data, and push email on to a completely different 'service provider'; I assume you have some sort of business logic tier that will orchestrate this?
I can't talk in terms of 'best practice' from experience (for email specifically), but abstracting out the email service (just like you'd abstract out data-access) is definitely on the right path, and that's probably the critical decision you need to make right now. You could then have different implementations of the email (including SQL, if you really wanted to).
Depending on volumes - do you look at an asynchronous call or synchronous call? WCF seems like a good candidate to handle comms - this would allow you to fire data (for emails) into an end-point that had a queue built into it, or you could call (via WCF) a web service that acted synchronously.
You can send mail via sql-server. For more refer this
The architecture of it is here
Another implementation of sending mail via c# is this as they have developed an email factory for implementation... hope this helps
sp_send_dbmail places the mail request into a queue in msdb. After the transaction that sent the mail commits, the queue activates an external process that handles the SMTP delivery, including retries, logging and all that. Overall system is quite resilient, scalable and performant.
Perhaps you're using the old, deprecated xp_sendmail based system?
I would like to track messages sent and received though Windows Live Messenger. I would then like to collate these messages into a database (not in the scope of this question).
The question is how and where should I track these messages. The simplest way it to force all clients to keep history files and read those, but it is not really the solution that I am looking for. Is there a way to track them from a server running in the same domain, I have read a little into Windows Communicator, I have also seen a lot of people chat about http://dev.live.com/messenger/ but I was hoping that someone may have addressed this problem already :)
I would like to do this using C# .NET 3.5
Check out MSNPSharp. Its a .NET msn library. Its very powerful and allows you to sign in from multiple locations. So you can sign in and listen to other conversations happening on a given account.
Its very straight forward to use. Download the full source code, there's a sample application that demonstrates its use in full detail.
http://code.google.com/p/msnp-sharp/
Here is two idea that might work.
The first one is the easiest but can be easily avoided by the user if he doesn't want to be logged. It would be to use MSN Plus over the MSN. With MSN Plus you have an API that let you get all messages from any Chat Windows... and a lot more. Of course, if the user is not you, the user can simply uninstall Msn Plus and your program will not log any data.
The second idea is better if you have a network that you require to check all Msn Conversation. If you use WireShark you can see that conversation are not crypted (well the last time I did it) and you can check the port and protocol to simply get the data from the network.
Hope it gives you a way to what you need.
Just two ideas
1. First the standard MSN protocol is plain text (from what I understand) so you could intercept the messages on the firewall and then put them in the DB and do the correlation there.
2. If this is in an organisation you could use Office Communicator which is the "corporate" version of MSN and has that functionality built in already. You can then just go in via their SDK and get the correlated data.
I managed to find two ways of doing this, though both are not really programmatic solutions, so may not appeal to this audience.
Make use of a Jabber gateway to set up forwards between your jabber client and the other IM networks. Traffic flows between your jabber enabled client and the jabber server via the jabber server. The Jabber server then translates this to the destination networks protocol and forwards the message. Likewise messages from the external IM networks are routed and translated by the Jabber server. An example of this is PSI <-> IceWarp Merak <-> MSN
Make use of Symantec IM Manager to intercept messages from the messaging clients on your network. You will need to either use host files or local DNS rules to convince the your local PCs that Messenger.hotmail.com is actually located at 192.168.0.59 and not at Microsoft.
Hope it helps other people that may want to do the same.
I hope someone can guide me as I'm stuck... I need to write an emergency broadcast system that notifies workstations of an emergency and pops up a little message at the bottom of the user's screen. This seems simple enough but there are about 4000 workstations over multiple subnets. The system needs to be almost realtime, lightweight and easy to deploy as a windows service.
The problem started when I discovered that the routers do not forward UDP broadcast packets x.x.x.255. Later I made a simple test hook in VB6 to catch net send messages but even those didn't pass the routers. I also wrote a simple packet sniffer to filter packets only to find that the network packets never reached the intended destination.
Then I took a look and explored using MSMQ over HTTP, but this required IIS to be installed on the target workstation. Since there are so many workstations it would be a major security concern.
Right now I've finished a web service with asynchronous callback that sends an event to subscribers. It works perfectly on a small scale but once there are more than 15 subscribers performance degrades considerably. Polling a server isn't really an option because of the load it will generate on the server (plus I've tried it too)
I need your help to guide me as to what technology to use. has anyone used the comet way with so many clients or should I look at WCF?
I'm using Visual C# 2005. Please help me out of this predicament.
Thanks
Consider using WCF callbacks mechanism and events. There is good introduction by Juval Lowy.
Another pattern is to implement blocking web-service calls. This is how GMail chat works, for example. However, you will have to deal with sessions and timeouts here. It works when clients are behind NATs and Firewalls and not reachable directly. But it may be too complicated for simple alert within intranet.
This is exactly what Multicast was designed for.
A normal network broadcast (by definition) stays on the local subnet, and will not be forwarded through routers.
Multicast transmissions on the other hand can have various scopes, ranging from subnet local, through site local, even to global. All you need is for the various routers connecting your subnets together to be multicast aware.
This problem i think is best solved with socket.
Open a connection to the server, and keep it open.
Could you have a slave server in each subnet that was responsible for distributing the messages to all the clients in the subnet?
Then you could have just the slaves attached to the central server where the messages are initiated.
I think some of you are vastly overthinking this. There is already a service built into every version of Windows that provides this exact functionality! It is called the Messenger service. All you have to do is ensure that this service is enabled and running on all clients.
(Although you didn't specify in the question, I'm assuming from your choices of technology that the client population of this network is all Windows).
You can send messages using this facility from the command line using something like this:
NET SEND computername "This is a test message"
The NET SEND command also has options to send by Windows domain, or to specific users by name regardless of where they are logged in, or to every system that is connected to a particular Windows server. Those options should let you easily avoid the subnet issue, particularly if you use domain-based security on your network. (You may need the "Alerter" service enabled on certain servers if you are sending messages through the server and not directly to the clients).
The programmatic version of this is an API called NetMessageBufferSend() which is pretty straightforward. A quick scan of P/Invoke.net finds a page for this API that supplies not only the definitions you need to call out to the API, but also a C# sample program!
You shouldn't need to write any client-side code at all. Probably the most involved thing will be figuring out the best set of calls to this API that will get complete coverage of the network in your configuration.
ETA: I just noticed that the Messenger service and this API are completely gone in Windows Vista. Very odd of Microsoft to completely remove functionality like this. It appears that this vendor has a compatible replacement for Vista.