SoorajSNBlaze333 / AOS-Project-1

Project 01 - Distributed Network

Create a simple distributed network. There is a sender that communicates with the mid-server. The mid-server forwards the messages from the client to the dedicated the Group server.

1.Project Analysis

Here we need first split the problem into 2 sections (Server and Client). We can visualize that the Sender and Mid-Server is going to follow a server-client architecture and the Client and Group-server is again going to follow another server-client architecture. We will be using Java language to create this distributed system.

2. Flowchart

3. Overview & Basic Setup

We will start with the Client/Sender application.

3.a. Sender Program

• Let's create a SivadasanNairP1Sender.java file.
• We will get the IP address of the MidServer from the command line arguments such as java SivadasanNairP1Sender 127.0.0.1
• We will recieve the argument passed from the command line to use as the IP Address (We will keep static port numbers).
• We will now create a socket object to connect to the server. Along with the socket, we also need to have a input stream and output stream to recieve and send messages from and to the server socket. We will be using the Socket, DataInputStream, DataOutputStream and BufferedReader.
• Next we need to create a variable that will store the input that is coming from the server.
• Next let's keep listening for any message that comes to the sender using a while loop. We will listen for a connection-closed to terminate the connection. The code inside the while loop will always be executed as long as the server keeps responding to the client.
• Let's have simple response handler functions, basically print statements which will let us know what kind of a message is coming from server. This was inspired from a web client-server request-response architecture.
• Here, let's create a generic function called print(String message) to display any string message. This was a good approach when there was a need for using System.out.println multiple times in the same file.

 public static void print(String message) {
   System.out.println(message);
 }

• We need to close all the objects related to socket, which includes the socket itself and the input and output streams.

3.b. MidServer Program

• Let's create a SivadasanNairP1MidServer.java file.
• We will get the IP address of the Group Server of the Sender from the command line arguments such as, java SivadasanNairP1MidServer 127.0.0.1
• The MidServer keeps track of the user's authentication status using an Auth class. The Auth class is reponsible for login and logout of the user.
• The Auth class keeps track of the user's authentication status.
• Then we write a simple login function, that uses the username and password and compares it to the username and password in the file auth/userList.txt.
• Now we will transfer the connection of the Sender from the MidServer to one of the group servers. In our case we will be using 3 types of Group servers (silver, gold and platinum). We will open the socket communication to the server only once the user is an authenticated user.
• After successfully logging in, we will send the Sender a message to terminate its connection to the Sender and also send the IP address of the Group server it needs to connect to.
• The MidServer will also send the user's points to the Group Server, so that the Group Server can keep track of the user's purchase points.
• We will close all our socket objects to prevent any memory leaks.

3.c. GroupServer Program

• Let's create a SivadasanNairP1GroupServer.java file.
• For our group server we will create a Threadpool that can create a thread for every group server.
• Each thread is responsible for creating a server object.
• Based on the type of the server, the Thread will excute the run method, which recieves the message from the sender
• Once the Sender is connected to the Group Server, the group server fetches the items from the data file once and loads into the program.
• The Sender can now use ls and numeric commands to fetch the list of items that are available for purchase and its corresponding points.
• The Sender needs to choose a number from the list of items and the Group Server will deduct the cost of the item from the points of the user.
• The Sender can keep purchasing until his/her points are empty.
• The Group Server can be closed from the Sender with the close command.

Screenshots and Test Runs

1.Silver Server

2.Gold Server

3.Platinum Server