#data-transfer #udp #udp-packet #connection #real-time #stream #internet


Provides ordered, mixed-reliability, and congestion-controlled data transfer over UDP

7 releases (4 breaking)

0.7.1 Jan 7, 2023
0.7.0 Nov 25, 2022
0.6.1 May 22, 2022
0.6.0 Mar 28, 2022
0.3.1 Jan 23, 2022

#1501 in Network programming

31 downloads per month

MIT license

6.5K SLoC


UFlow is a Rust library and UDP networking protocol for realtime internet data transfer, with a focus on simplicity and robustness. Though it has been designed from the ground up, UFlow's interface and functionality are inspired by the venerable ENet library.


  • Packet-oriented data transfer between two hosts
  • Automatic packet fragmentation and reassembly according to the internet MTU (1500 bytes)
  • 3-way connection handshake for proper connection management
  • Up to 64 independently sequenced packet streams
  • 4 intuitive packet transfer modes: Time-Sensitive, Unreliable, Persistent, and Reliable
  • TCP-friendly, streaming congestion control implemented according to RFC 5348
  • Efficient frame encoding and transfer protocol with minimal packet overhead
  • CRC validation for all transmitted frames (Polynomial: 0x132c00699)
  • 100% packet throughput and an unaffected delivery order under ideal network conditions
  • Water-tight sequence ID management for maximum dup-mitigation
  • Application-configurable receiver memory limits (to prevent memory allocation attacks)
  • Nonce-validated data acknowledgements (to prevent loss rate / bandwidth spoofing)
  • Resilient to DDoS amplification (request-reply ratio ≈ 28:1)
  • Meticulously designed and unit tested to ensure stall-free behavior
  • Threadless, non-blocking implementation


Documentation can be found at docs.rs.


Although a previous version is described in the whitepaper, much has changed about the library in the meantime (including the name!). The current version has the following improvements:

  • TCP-friendly congestion control implemented according to RFC 5348
  • Receiver memory limits (for packet reassembly)
  • No sentinel packets or frames
  • An additional packet send mode which causes packets to be dropped if they cannot be sent immediately (Time-Sensitive)
  • No iteration over the number of channels

The new design will soon™ be summarized in an updated whitepaper.