What are some ideal ways to build a chat application?

If I wanted to build a chat application that can chat with other users that are on the website and host chatrooms what would be some ideal ways? If there are some open source ones开发者_如何学编程 out there? If I build from scratch what should I use (i heard comet is good)? Thanks!

If you are planning to build one by yourself, looks at the Subscribe and Publisher pattern. You can use remoting or just socket programming with a centralised server to capture and transmit messages to the respective users.

If you still need an open source chat SDK, you can try ConnectyCube. They provide also a backend and you can register a free account to check the solution.
Also there is REST API allowing you to add functionality not available in SDKs or writing chat in other languages if you need. You might also find this article useful. It compares products of several providers.