This was done as a part of Distributed Systems course at The University of Minnesota.

In this project, we have implemented a simple publish subscribe system. We have used 2 forms of communication, UDP and Java RMI to achieve this. The components of this system are clients, group servers and a registry server.

• The client-side functionality is implemented in the Client package, with two files, Client.java and PublishedClient.java.
• Client.java handles the RPC connection to the server, where it joins a server, subscribes, unsubscribes and/or publishes an article, and leaves a server.
• This also handles the connection to the Registry Server to get the list of active servers for the client to connect.
• PublishedClient.java runs on a separate thread that handles the UDP connection between the client and the server.
• It receives the published article from the server.

• The server-side functionality is written in the Server package, with Communicate.java (interface), CommunicateImpl.java which has the core functionality of the publisher-subscriber system, a) CommunicateHelper.java for the helper functions to validate requests, and connect to the Registry Server, b) GroupServer.java which registers itself to the registry server and helps in propagating the publisher-subscriber system by using the client’s request, c) GroupServerHeartbeat.java which handles the connection with the Registry Server.
• If the registry server does not receive a heartbeat from the group server for 5 seconds, it deregisters the server automatically.

• It has a list of servers and their IPs and Port numbers in case a new client wants to join the system.
• It also listens to hearbeats from the servers. If there is a failure, there is a failover case which is implemented which allows the client to automatically switch to a running server.
• This was already given for the sake of this project. (Written in C and uses Linux RPC calls)

• To run the project, there is a file called artifacts.zip which contains all the jar files required.

• There is one jar file called pubsub_srv.jar, which runs the Group Server instance. It can be run on several machines.

• Then there are multiple client jars, each of which has a defined role, done specifically for testing different scenarios (more details in the Clients section). The filenames are pubsub_clnt.jar, pubsub_clnt1.jar, pubsub_clnt2.jar, pubsub_clnt3.jar.

• Now, the first step is to ensure that the RMI registry (Registry Server) is up and running on one of the machines.

java -jar pubsub_srv.jar

java -jar pubsub_clnt.jar

• Bhaargav Sriraman (srira048)
• Soumya Agrawal (agraw184)
• Garima Mehta (mehta250)

For more information please refer the project document.