P2P File Sharing System

A simple peer-to-peer (P2P) file sharing system for distributed P2P communication, inspired by Gnutella. Whenever a node wants to download a file, it broadcasts its request across the network. Other nodes that have the requested file (or a similar one) respond with their offers. Finally, the user selects one of these offers, and the file transfer takes place.

📌 Features

• Decentralized peer-to-peer file sharing
• Configurable network topology via a .conf file
• Message types for:
  • Discovery – find files across the network
  • Offer – return matching files from peers
  • Ack – confirm file selection
  • Metadata – provide file details before transfer
  • Data – transfer raw file chunks
• Supports intermediate routing between peers (not just direct connections)
• Resilient against flooding with sequence numbers and aging mechanism
• CLI interface for easy interaction

Communication Protocol

1. Discovery Phase

A peer broadcasts a query (file name) to its neighbors. Duplicate queries are avoided using (sequence_number, host_id) tuples.

2. Offer Phase

Peers respond with a list of matching files if they have them.

3. Ack Phase

The requester selects one of the offers and sends an acknowledgment.

4. Metadata Transfer

Metadata of the file (e.g., file size) is sent first.

5. Data Transfer

Finally, the raw file chunks are transferred peer-to-peer. Intermediate peers forward packets if needed.

Execution

1. Configure Topology

Make sure all your nodes are connected to each other in a single network. Edit topology.conf to define your peer and its neighbors:

[Self]
HOST_ID = 1

[Neighbours]
HOST_IPS = 192.168.1.197, 192.168.1.156, 192.168.1.155

Each peer needs a unique HOST_ID and a list of neighbor IPs.

2. Prepare Repository Folders

Inside the project’s root directory, the repository/ folder must contain:

• tx/ → files you want to share
• rx/ → files you will receive

3. Run the Peer

Start a peer with:

python3 peer.py

• The peer will load the network configuration.
• You can issue queries for files.
• The system will list available offers from other peers.
• Select an offer, and the file will be transferred.

Demo

We present a file transfer scenario involving three nodes arranged in a linear topology: [Node1] → [Node2] → [Node3]. In this setup, Node 1 requests a PDF file that is available on Node 3. Since they are not directly connected, Node 2 serves as an intermediary, forwarding the file from Node 3 to Node 1.

To demonstrate the system’s robustness, the Wi-Fi connection of the intermediate node is intentionally disconnected during the transfer, triggering the error-handling mechanisms.

Node 1:

Node 2:

Node 3: