Difference between a Message Broker and an ESB

Question

I have gone through different questions/articles on Message Brokers and ESBs(Even on stackoverflow). Still not a clue as what is the CLEAR demarcating difference between an Mess

Answer 1

I just read this article by Udi Dahan a few days ago, which might give you a more clear view of what I feel is one fundamental difference.

http://www.udidahan.com/2011/03/24/bus-and-broker-pubsub-differences

Quoting:

The rule that there can only be a single publisher for a given event type is one of the things that differentiates buses from brokers, though both obviously allow you to have multiple subscribers

...

Unfortunately, there are many broker-style technologies out there that are being marketed under the banner of the Enterprise Service Bus. While some products have the ability to be deployed in both a centralized and distributed fashion (sometimes called “federated” or “embedded” mode), many do not enforce the “single publishing endpoint per event-type” rule.

Without this constraint, it is just too easy to make mistakes.

Hope it helps.