CS241 - Operating System - 1 - Assignment 2 - Java Synchronizatio - Solved

 Problem  Definition
It is required to simulate a limited number of devices connected to a router’s Wi-Fi using Java threading and semaphore. Routers can be designed to limit the number of open connections. For example, a Router may wish to have only N connections at any point in time. As soon as N connections are made, the Router will not accept other incoming connections until an existing connection is released. Explain how semaphores can be used by a Router to limit the number of concurrent connections

 

 The  following  rules  should  be  applied:

➔ The Wi-Fi number of connected devices is initially empty.

➔ If a client is logged in (print a message that a client has logged in) and if it can be served

➔ (means that it can reach the internet), then the client should perform the following activities:

◆  Connect

◆  Perform online activity

◆  Log out

➔ Note: these actions will be represented by printed messages, such that there is a random

➔ waiting time between the printed messages when a client connects, do some online ➔ activities and logged out.

➔ If a client arrives and all connections are occupied, it must wait until one of the currently ➔ available clients finish his service and leave.

➔ After a client finishes his service, he leave and one of the waiting clients (if exist) will ➔ connect to the internet.

 Solution  Design
 You  program  must  contain  the  following classes: 

1.  Router Class: that contains a list of connections and methods to occupy a connection and release a connection.

2.  Semaphore Class: as given the synchronization lab.

3.  Device Class: represent different devices (threads) that can be connected to the router; each device has its own name (i.e. C1) and type (i.e. mobile, pc, tablet...) and it may perform three activities: connect, perform online activity and disconnect/logout.

4.  Network Class: this class contains the main method in which the user is asked for two inputs:

●      N: max number of connections a router can accept ●    TC: total number of devices that wish to connect).

●      TC lines that contain: name of each device, and its type

 Program  Output
You will print the output logs in a file, which simulates the execution order of the devices threads and the printed messages of each device

NOTE THAT: This is just an example not the only scenario that can be applied.

 Sample  Input
What is the number of WI-FI Connections?

2 What is the number of devices Clients want to connect?

4

C1 mobile

C2 tablet

C3 pc

C4 pc

 Sample Output
-  (C1)(mobile)arrived- (C2)(tablet)arrived

-  Connection 1: C1 Occupied- Connection 2: C2 Occupied

-  C4(pc) arrived and waiting

-  C3(pc)arrived and waiting- Connection 1: C1 login

-  Connection 1: C1 performs online activity- Connection 2: C2 login

-  Connection 2: C2 performs online activity

-  Connection 1: C1 Logged out

-  Connection 1 : C4 Occupied- Connection 1 : C4 log in

-  Connection 1 : C4 performs online activity

-  Connection 2: C2 Logged out- Connection 2: C3 Occupied

 Grading  Criteria 

Router Class                                                                                                        
         10
Semaphore Class                                                                                                
          5
Device Class                                                                                                        
        10
Network Class                                                                                                      
        10
Output Valid Order (Code Run Properly)                                                             
        20
GUI - Bonus (That shows the behavior of connections when occupied or         released by a particular device)
        10