networkcalc

NetworkCalc is a simple client-server application using Java sockets that allows multiple clients to send arithmetic expressions to a centralized server, which evaluates the expressions and returns the computed results. ("Calc" is slang for calculator, btw.)

This project demonstrates basic networking, concurrency, and protocol design in Java.

Requirements

• Java 21 or later.

How to Compile

First, clone or download the project files, then open a terminal or command prompt in the project root directory.

On a Unix system, compile the server and client source files using:

make

On Windows, you may use:

.\build.bat compile

This will produce MathServer.class and MathClient.class in the bin/ project sub-directory.

How to Run

1. Start the Server

Unix:

make run-server

Windows:

.\build.bat run-server

This will start the server listening on port 12345.

Note: A logs/ sub-directory will be created automatically, and a fresh server.log file will be generated for each server run.

Shutting Down the Server:
To gracefully terminate the server, simply type quit in the terminal where the server is running and press Enter. This will immediately close all active connections and exit the application.

2. Start a Client

In a new terminal window, run:

Unix:

make run-client

Windows:

.\build.bat run-client

You will be prompted to enter your name once the client is running. After connecting to the server, the client will randomly generate and send three arithmetic expressions at random intervals to the server. Then, it will disconnect automatically.

You can open multiple clients at once to simulate multiple users connecting and interacting with the server simultaneously.

Messaging Protocol

The app uses the following message types for communication between client and server.
Each message is implicitly terminated with a newline character \n.

1. Protocol Message Types

a. Client-to-Server Messages

• Connection Request (JOIN):

  • Format: JOIN:<ClientName>
  • Example: JOIN:Alice

• Calculation Request (CALC):

  • Format: CALC:<ClientName>:<ArithmeticExpression>
  • Example: CALC:Alice:12+7*3

• Disconnection Request (LEAVE):

  • Format: LEAVE:<ClientName>
  • Example: LEAVE:Alice

b. Server-to-Client Messages

• Acknowledgment (ACK):

  • Format: ACK:<ClientName>:<ServerMessage>
  • Example: ACK:Alice:Welcome

• Calculation Response (RES):

  • Format: RES:<ClientName>:<Result>
  • Example: RES:Alice:33

• Error Message (ERR):

  • Format: ERR:<ErrorDescription>
  • Example: ERR:Invalid Expression Format

Server Logging Format

The server writes events to the console and into logs/server.log in the following format:

• Log Entry Format: [YYYY-MM-DD hh:mm:ss] <EVENT> - <ClientName>: <Details>

• Examples:

  • Connection: [2025-04-15 14:30:25] CONNECT - Alice: Connected from 127.0.0.1:54321
  • Calculation Request:
    [2025-04-15 14:31:00] CALC_REQUEST - Alice: Expression received: 12+7*3
  • Calculation Response:
    [2025-04-15 14:31:05] CALC_RESPONSE - Alice: 12+7*3 = 33
  • Disconnection:
    [2025-04-15 14:32:00] DISCONNECT - Alice: Client disconnected after 120 seconds