Network Packet Analysis Chat Application

A sophisticated C-based client-server chat application that combines real-time messaging with advanced network packet analysis capabilities. This application captures and analyzes network traffic while facilitating multi-client chat communication.

Features

Chat Functionality

• Multi-client support: Server can handle up to 10 concurrent clients
• Real-time messaging: Instant message broadcasting between connected clients
• Connection management: Automatic client connection/disconnection handling
• Cross-platform networking: Uses standard POSIX socket programming

Network Analysis

• Live packet capture: Real-time network packet interception using libpcap
• Protocol analysis: Detailed breakdown of TCP, UDP, ICMP, and other protocols
• Packet statistics: Comprehensive traffic analysis and reporting
• Jitter calculation: Network performance measurement with jitter analysis
• Packet loss estimation: Simulated packet loss rate calculation
• Traffic logging: Automatic packet capture to .pcap files

Performance Monitoring

• Real-time statistics: Live display of network metrics
• Protocol distribution: Percentage breakdown of different protocols
• Network quality metrics: Jitter and packet loss measurements
• Periodic reporting: Automated statistics updates every 10 seconds

Requirements

System Dependencies

• Linux/Unix-based operating system
• Root privileges (required for packet capture)
• Network interface access

Libraries

• libpcap-dev - Packet capture library
• Standard C libraries (stdio, stdlib, string, unistd, etc.)
• POSIX socket libraries
• Network interface libraries

Usage

Starting the Server

sudo ./packet_chat server

Important: Root privileges are required for packet capture functionality.

The server will:

• Display the local IP address and port (default: 8080)
• Begin listening for client connections
• Start capturing network packets on eth0 interface
• Create a chat_packets.pcap file for packet logging
• Display periodic network statistics

Connecting as Client

./packet_chat client

Clients can:

• Connect to the server automatically using local IP detection
• Send messages that are broadcast to all other connected clients
• Receive messages from other clients in real-time
• Disconnect gracefully

Sample Server Output

Server is running on IP: 192.168.1.100, Port: 8080
Waiting for connections...
New client connected. Socket fd is 4, IP is : 192.168.1.101, port : 54321

--- Packet Analysis ---
Packet Length: 74 bytes
Source MAC: aa:bb:cc:dd:ee:ff
Destination MAC: 11:22:33:44:55:66
Source IP: 192.168.1.101
Destination IP: 192.168.1.100
Protocol: TCP

--- Packet Statistics ---
Total Packets: 150
TCP Packets: 120 (80.00%)
UDP Packets: 25 (16.67%)
ICMP Packets: 3 (2.00%)
Other Packets: 2 (1.33%)
Network Jitter: 2.45 ms
Packet Loss: 0.67%

Configuration

Modifiable Constants

#define PORT 8080              // Server port
#define MAX_BUFFER 1024        // Message buffer size
#define MAX_CLIENTS 10         // Maximum concurrent clients
#define MAX_PACKET_HISTORY 1000 // Packet history for jitter calculation

Network Interface

By default, the application captures packets on eth0. To change the interface, modify this line in the start_server() function:

handle = pcap_open_live("eth0", BUFSIZ, 1, 1000, errbuf);

Architecture

Core Components

1. Socket Server: Multi-client TCP server using select() for non-blocking I/O
2. Packet Capture Engine: libpcap-based network traffic interception
3. Protocol Analyzer: Deep packet inspection for various network protocols
4. Statistics Engine: Real-time calculation of network performance metrics
5. Client Handler: Manages multiple simultaneous client connections

Data Structures

• PacketStats: Comprehensive packet analysis data structure
• Client socket array: Manages multiple client connections
• Packet history buffer: Stores timestamps for jitter calculation

Security Considerations

• Root Privileges: Required for raw packet capture - use with caution
• Network Exposure: Server binds to all interfaces (INADDR_ANY)
• Buffer Management: Input validation and buffer overflow protection implemented
• Resource Limits: Built-in limits on clients and packet history

Limitations

• Platform Specific: Designed for Linux/Unix systems
• Interface Dependency: Hardcoded to eth0 network interface
• Root Required: Packet capture requires administrative privileges
• Local Network: Designed for local network communication
• Simulated Metrics: Some packet loss calculations are estimated

Output Files

• chat_packets.pcap: Binary packet capture file compatible with Wireshark and other network analysis tools