RUFShare

RUFShare (Reliable UDP File Sharing) is a lightweight file transfer library built on top of UDP, designed to provide reliable file delivery while maintaining the performance advantages of connectionless communication.

The library implements a custom protocol that handles:

• Peer discovery
• File transfer negotiation
• Chunked data transmission
• Integrity verification using CRC16/CRC32
• Acknowledgement and retransmission mechanisms

RUFShare is written in pure C99 and targets Unix-like systems.

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Features

• Reliable file transfer over UDP
• Custom packet-based protocol
• Peer discovery through broadcasting
• Chunked file transmission
• CRC-based data integrity validation
• Shared library interface
• Minimal external dependencies
• Suitable for embedded, networking, and systems programming projects

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Protocol Overview

RUFShare uses four packet types:

Packet	Purpose
CAST	Peer discovery and broadcasting
SEND	File transfer metadata
FLOW	File data chunks
RECV	ACK/NACK responses

Transfer Flow

Sender                     Receiver
  |                             |
  |-------- CAST -------------> |
  | <------ CAST -------------- |
  |                             |
  |-------- SEND -------------> |
  | <------ ACK --------------- |
  |                             |
  |-------- FLOW -------------> |
  | <------ ACK/NACK ---------- |
  |                             |
  |-------- FLOW -------------> |
  | <------ ACK/NACK ---------- |

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Project Structure

include/
├── broadcast.h
├── cntl.h
├── data.h
├── file_stream.h
├── net_stream.h
├── puller.h
├── pusher.h
├── scanpair.h
├── tryexec.h
└── protocol/

source/
├── broadcast.c
├── cntl.c
├── data.c
├── file_stream.c
├── net_stream.c
├── puller.c
├── pusher.c
└── ...

library/
├── librufshare.so
└── libcrc.a

---

Building

PCC (default)

make

GCC

make CC=gcc

Generated library:

library/librufshare.so

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Public API

Initialize the library:

status_t initiate(const char *logpath, size_t logcount);

Shutdown:

status_t deinitiate(void);

Send a file:

status_t push_file(
    InitConfig *config,
    const char *path
);

Receive a file:

status_t pull_file(
    InitConfig *config,
    char *remote_name
);

Broadcast presence:

status_t broadcast(
    InitConfig *config
);

Discover peers:

status_t scanpair(
    InitConfig *config,
    PairInfo **info,
    size_t *len
);

---

Example

#include "rufshare.h"

int main(void)
{
    if (initiate("./logs", 1024) != SUCCESS)
        return 1;

    InitConfig cfg = {
        /* configuration */
    };

    push_file(&cfg, "example.bin");

    deinitiate();

    return 0;
}

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Reliability

RUFShare achieves reliability through:

• Sequence numbers
• ACK/NACK packets
• CRC16 validation for control packets
• CRC32 validation for data packets
• Chunk-based transmission

Unlike TCP, the protocol is application-defined and optimized specifically for file transfer workloads.

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Use Cases

• Local network file sharing
• Embedded device communication
• Custom networking applications
• Educational networking projects
• UDP protocol experimentation

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Requirements

• POSIX-compatible operating system
• C99 compiler
• pthread
• mmap support

Tested with:

• PCC
• GCC

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License

This project is licensed under the terms provided in the LICENSE file.