C#, WCF, want to make a chat application, what binding should I use? maybe some examples?

Question

I am looking forward to make a sort of a chat application using C# and WCF, yet before I start I wanted to clear a few things, so that I don't get carried in the wrong direction. :)

• the application should be able to both make event ( send messages ) and listen to events ( receive messages ), therefor if I understand it right, the application should be both the client and the server at once?

• what binding should I use? If I understand right, basicHttp binding hard to configure and is used when a WCF app needs to connect to non-WCF app? While for connecting two WCF apps its better to use NetTcpBinding?

• how would this applications find each other, considering that they are running on different machines? should there be a central server, to which the app would connect first, saying "I'm user123, my IP is that and that, I'm free for chat" and look for other user IP addresses there? Or is there some other ways for apps to find each other without the central server?

• maybe you could direct me to some examples or tutorials on this topic? ( tried googling, no luck ).

Thanks! :)

Answer 1

There is no right and wrong answer to your question - it all depends on what you require. You then can choose the best architecture for your needs, and then the best technology for that architecture.

There are two things to consider - how will users find people to chat to, and then once they have found someone - how do the applications connect to each other.

For users to find each other, you either need to connect to a central server, which will then show a list of all connected users, or users need to enter the IP address of the person they want to chat to. Note that some firewalls will block incoming connections in this second case, so this may not be feasible in some cases.

Next, once you have found the person you wish to chat to, you need to decide whether messages will route directly to the other user, or if you want to continue to go through a central server.

If you choose to go through a central server, then your application will be functioning as a client, and will therefore pass through firewalls without a problem. However if you connect directly to the other user, both copies of the application will be acting as a client and a server (P2P topology), and therefore firewalls may be an issue. Having said that, you could designate one of the applications to be a server, with the other acting as a client, in which case only the server side needs to worry about the firewall.

Without knowing exactly what you are trying to achieve, it is hard to recommend which architecture will work best for you.

Answer 2

You can use netPeerTcpBinding.

See also:

http://blogs.interknowlogy.com/2009/08/05/building-a-really-simple-wcf-p2p-application/

http://msdn.microsoft.com/en-us/library/bb690929(v=vs.90).aspx

http://www.codeproject.com/KB/WCF/Chat_application_using_WC.aspx

Answer 3

If your peers (machine that can operate as a client & server) are going to be behind NATs/firewalls then you will have a very very tough time building a chat application using WCF. If the peers will all be on the same network WCF is workable.

To write a chat application from scratch using WCF you will be re-inventing the wheel. Why not employ an existing protocol that's been designed precisely for the purpose such as XMPP. There are XMPP libraries around for .Net. You will need a central server but if you use XMPP you could feasibly piggyback onto one of the many existing free servers.