Publish Subscriber vs Observer pattern

Publish Subscriber is related to the software applications running on different nodes and want to exchange data between them using Events and Notifications. Communication is done via web server that keeps track of all subscribers. When a user logs in his IP is registered to the web server this IP information is used route the events to the subscribers. But there must be handlers on the various subscribers those execute their logic. 

• This how different applications hosted on different nodes communicate with one another.
• This same event-handling mechanism is implemented for the objects with in the same application process.
• This same event-handling mechanism is implemented for different processes executed under a process. This is how the inter process communication is implemented.