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FRP – Ferris Reliable Protocol

FRP is a reliable custom protocol built on top of UDP in Rust. It uses Selective Repeat ARQ (SR) to ensure data reliability and supports:

• Custom connection handshake (SYN / SYN-ACK / ACK) and graceful disconnect (FIN / FIN-ACK).
• Message and file transfer with fragmentation and reassembly.
• Data integrity check using CRC32.
• Positive (ACK) and negative (NACK) acknowledgements for lost/corrupted packet recovery.
• Sliding window for efficient transmission.
• Packet loss simulation for testing the protocol.
• Heartbeat packets for connection state monitoring.
• CLI interface with user commands.

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Installation & Running

1. Clone the repository:

git clone https://github.com/zimka1/udp_transfer
cd udp_transfer

2. Build:

cargo build --release

3. Run:

cargo run -- <local_port> <peer_ip> <peer_port>

• <local_port> — port for the local instance to listen on.
• <peer_ip> — peer IP address.
• <peer_port> — peer port.

Example:

cargo run -- 5000 127.0.0.1 6000

On the other side:

cargo run -- 6000 127.0.0.1 5000

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CLI Commands

• help — show available commands.
• connect — initiate connection.
• disconnect — gracefully disconnect.
• change mode — toggle packet loss simulation.
• change repo (<path>) — change the directory for saving received files.
• send message (<text>, <fragment_size>) — send a message split into fragments.
• send message (<text>) — send a message without fragmentation.
• send file (<file_name>, <fragment_size>) — send a file split into fragments.
• send file (<file_name>) — send a file without fragmentation.

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Project Structure

• main.rs — application entry point, CLI, and state machine.
• send.rs — message/file sending logic, sliding window, CRC32.
• receiver.rs — packet receiving, ACK/NACK handling, reassembly.
• reassembler.rs — assembling fragmented messages and files.
• packet.rs — packet structure and serialization.
• state.rs — connection state machine.
• commands.rs — CLI command parsing.
• change.rs — handling repository/mode change commands.

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Protocol Features

• Reliable UDP: Selective Repeat ARQ with ACK/NACK and retransmissions.
• Sliding Window: Increases transfer speed without waiting for each packet acknowledgment.
• CRC32: Ensures packet integrity.
• Heartbeat: Detects connection loss.