NetworkProgramming - Network Programming  - Homework 4 - Bulletin Board System - Solved

Pub/Sub system 


1. Introduction
In this part, you are going to implement the subscription features for the BBS service. The event will be raised whenever the client creates a new post that title contains the keyword subscribed by any other client. 

2. Example Architecture using Apache Kafka
The middleware server will get a message/record from the producer when there has a new post and also notify the client(s) who have subscribed to the specified topic. 

A.    BBS server is a producer, and each client is a consumer 

  

B.     Each client act as both a producer and a consumer 

  

Requirements 
The service can serve at least 10 clients. Your server and client program must be able to handle all commands in the previous part (output results must be the same as the previous part). For some commands such as whoami, exit, logout, create-board, list-board ##<key> and list-post <boardname> ##<key>, your client program only sends the command to the server and gets the corresponding result from the server. However, there are new commands that your client program will subscribe to the new post. These commands are described as follows: 

Command format 
Description 
Result 
subscribe --board <board-name>  

--keyword <keyword> 

(command and arguments are in the same line) 
Subscribe the board with a keyword, notify the client whenever the event be raised. 

Note [1]: Can subscribe the same board multiple times with different keywords. Notify user once someone creates a new post with a specified board and the title contains one of the keywords 

Note [2]: Subscribe objective (board) can be nonexistent 
Success 
Subscribe successfully (The notify message should at least include board, title, and author) 
Fail (1) 
Please login first 
Fail (2) 
[Invalid option] usage: subscribe --board <boardname> --keyword 

<keyword> 
Fail (3) 
Already subscribed 
subscribe --author <author-name> 

--keyword <keyword> 

(command and arguments are in the same line) 
Subscribe the author with a keyword, notify the client whenever the event be raised. 

 

Both notes [1] and [2] are same as the previous one (change objective to author) ↑ 
Success 
same as the previous one 
Fail (1) 
same as the previous one 
Fail (2) 
[Invalid option] usage: 

subscribe --author <authorname> --keyword 

<keyword> 
Fail (3) 
same as the previous one 
unsubscribe --board <board-name> 
Unsubscribe the board from the server (or middleware server) and remove all the keywords associated with a specified board. 
Success 
Unsubscribe successfully 
Fail (1) 
Please login first 
Fail (2) 
You haven't subscribed 

<board-name> 
unsubscribe --author <author-name> 
Unsubscribe the author from the server (or middleware server) and remove all the keywords associated with a specified author. 
Success 
Unsubscribe successfully 
Fail (1) 
Please login first 
Fail (2) 
You haven't subscribed 

<author-name> 
list-sub 
List the information about the subscribed board(s) and author(s). 
Success 
List all the subscribed info 
Fail (1) 
Please login first 
Scenario
Run your server first, and run your client program to connect to your server. The sample outputs of the client program are listed as follows: 

Client 1 
Client 2 
Client 3 
bash$ ./client 127.0.0.1 7777 

********************************  

** Welcome to the BBS server. **  ********************************  

% register Paul paul@cs.nctu.edu.tw 12345 

Register successfully. 
bash$ ./client 127.0.0.1 7777 

********************************  

** Welcome to the BBS server. **  ********************************  

% register Brad brad@cs.nctu.edu.tw 12345 

Register successfully. 
bash$ ./client 127.0.0.1 7777 

********************************  

** Welcome to the BBS server. **  ********************************  

% register Gary gary@cs.nctu.edu.tw 12345 

Register successfully. 
% login Paul 12345 Welcome, Paul. 
% login Brad 12345 Welcome, Brad. 
% login Gary 12345 Welcome, Gary. 
 
% subscribe --board HW4_Board  

--keyword Project 

Subscribe successfully 
% subscribe --author Jason --keyword hw4 

Subscribe successfully 

 
% create-board HW4_Board 

Create board successfully. 
  
  
  
% subscribe --board HW4_Board  

--keyword Project 

Already subscribed 

% subscribe --author Bryant  

--keyword exam 

Subscribe successfully 
% subscribe --author Paul --keyword HW 

Subscribe successfully 

% subscribe --author Paul --keyword post 

Subscribe successfully 

% unsubscribe --author Brad You haven't subscribed Brad 
% create-post HW4_Board  

--title About Project --content HW4… Create post successfully. 
  
 

% list-board ##HW 

   Index   Name       Moderator 


 
 
% create-post HW4_Board  

--title About HW and Exam --content blablabla 

Create post successfully. 
% unsubscribe --author Bryant 

Unsubscribe successfully 

 

 
 
 
% list-sub 

Board: HW4_Board: Project 

 



% list-sub