Multi-Stage DNS Resolver System

A high-performance 2-tier DNS resolution system implemented in C++ using socket programming, featuring intelligent caching and concurrent request handling.

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Features

• 2-Tier Architecture: Client → Proxy → DNS Server communication model
• Intelligent Caching: Proxy-layer caching reduces DNS server load
• Bidirectional Resolution: Supports both A-record (domain→IP) and PTR-record (IP→domain) queries
• Concurrent Processing: Multi-threaded server design supporting 100+ simultaneous clients
• Thread-Safe Operations: Proper synchronization primitives for concurrent access
• Persistent Cache: Cache survives server restarts for improved performance

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System Architecture

┌─────────────┐    ┌─────────────┐    ┌─────────────┐
│             │    │             │    │             │
│ DNS Client  │◄──►│ Proxy Server│◄──►│ DNS Server  │
│             │    │   (Cache)   │    │ (Database)  │
└─────────────┘    └─────────────┘    └─────────────┘
     Port: *           Port: 8081         Port: 8080

Components

• DNS Client (dnsClient.cpp): User interface for DNS queries
• Proxy Server (proxyServer.cpp): Caching layer with request forwarding
• DNS Server (dnsServer.cpp): Core resolution engine with domain database

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Prerequisites

• C++ Compiler: GCC 4.8+ or Clang 3.3+ with C++11 support
• Operating System: Linux or macOS
• Network Tools: netcat (nc) for testing
• Make: GNU Make for compilation

Installation Commands

Ubuntu/Debian:

sudo apt-get update
sudo apt-get install build-essential netcat-openbsd

macOS:

xcode-select --install
brew install netcat

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Installation & Setup

1. Clone the Repository

git clone https://github.com/Abhishek100100/Multi-Stage-DNS-Resolver-Using-Socket-Programming.
cd Multi-Stage-DNS-Resolver-Using-Socket-Programming

2. Compile the Project

make all

3. Verify Compilation

ls -la dns* proxy*
# Should show: dnsClient dnsServer proxyServer

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Quick Start

1. Start the DNS Server

./dnsServer 8080

2. Start the Proxy Server

./proxyServer 8081

3. Run the Client

./dnsClient 127.0.0.1 8081

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Usage Examples

Domain to IP Resolution

./dnsClient 127.0.0.1 8081
# Choose option 1, enter: google.com
# Output: 142.250.191.14

IP to Domain Resolution

./dnsClient 127.0.0.1 8081
# Choose option 2, enter: 142.250.191.14
# Output: google.com

Command Line Testing

echo "1:google.com" | nc 127.0.0.1 8081
echo "1:google.com" | nc 127.0.0.1 8080

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Load Testing

Run 100 Concurrent Clients Test

chmod +x test_100_clients.sh
./test_100_clients.sh

Expected output:

=== TEST RESULTS ===
Total clients: 100
Successful requests: 100
Success rate: 100%
Average response time: XXms

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Configuration

Database Configuration (database_mappings.txt)

google.com 142.250.191.14
facebook.com 157.240.241.35
github.com 140.82.114.3
stackoverflow.com 151.101.1.69
youtube.com 172.217.164.78
amazon.com 176.32.103.205

Port Configuration

• DNS Server: Port 8080 (configurable via command line)
• Proxy Server: Port 8081 (configurable via command line)
• Client: Connects to proxy server port

Cache Configuration

• Cache File: proxy_cache.txt
• Cache Policy: Persistent storage
• Cache Location: Same directory as executable

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Troubleshooting

"Address already in use" Error

pkill -f dnsServer
pkill -f proxyServer

"Connection refused" Error

lsof -i :8080  # DNS Server
lsof -i :8081  # Proxy Server

"NOT_FOUND" Responses

cat database_mappings.txt
# Restart DNS server to reload database

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Project Structure

Multi-Stage-DNS-Resolver-Using-Socket-Programming/
├── README.md
├── Makefile
├── allheaders.h
├── dnsClient.cpp
├── dnsServer.cpp
├── proxyServer.cpp
├── database_mappings.txt
├── proxy_cache.txt
├── test_100_clients.sh

📚 Technical References

• RFC 1035 - Domain Names Implementation
• Beej's Guide to Network Programming
• C++ Concurrency in Action