MiniTCP — A Reliable Transport Protocol over UDP

A lightweight user-space TCP protocol implementation built on top of UDP, featuring handshake, timeout retransmission, sliding window flow control, reliable in-order delivery, congestion control, fast retransmit, multi-connection support, and a high-level socket-like API.

Overview

Feature	Description
3-way handshake	SYN / SYN+ACK / ACK connection establishment
4-way termination	Full-duplex connection teardown
Dynamic RTO	Jacobson/Karels algorithm (RFC 6298)
Sliding window	Sender and receiver side flow control
Reliable delivery	In-order reassembly with out-of-order buffering
Congestion control	TCP Reno: slow start + AIMD
Fast retransmit	3 duplicate ACKs triggers immediate retransmission
Multi-connection	Reactor pattern with epoll
High-level API	BSD-socket-like ReliableSocket wrapper

For detailed protocol design and implementation notes, see Design.md.

Build & Run

Prerequisites

• CMake ≥ 3.14
• g++ ≥ 9.0
• Linux / WSL environment

Build

./build.sh

Clean

./clean.sh

All binaries are generated in ./build/. Switch to that directory before running any demo program.

Quick Start

Using ReliableSocket API (recommended)

Server:

ReliableSocket sock;
sock.listen(9000);
sock.accept();

auto data = sock.recv();
sock.close();

Client:

ReliableSocket sock;
sock.connect("127.0.0.1", 9000);

sock.send(data);
sock.close();

Using low-level API (file transfer)

// sender side
send_file(connection, udp, "./path/to/file");

// receiver side
recv_file(connection, udp, "./path/to/output");

Performance Benchmark

Tested on loopback interface with tc netem network emulation. File size: 1.5 MB.

Delay	Loss	Throughput	Time
10ms	0%	10.64 Mbps	1180ms
10ms	1%	1.26 Mbps	10001ms
10ms	5%	0.80 Mbps	15795ms
50ms	0%	6.95 Mbps	1808ms
50ms	1%	0.64 Mbps	19767ms
50ms	5%	0.21 Mbps	58844ms
100ms	0%	3.59 Mbps	3499ms
100ms	1%	1.49 Mbps	8429ms
100ms	5%	0.18 Mbps	69153ms

To reproduce:

sudo bash scripts/run_stress_test.sh
python3 scripts/analyze_results.py

Performance report:

Wireshark Analysis

See the step-by-step guide: Wireshark Tutorial

About Author

• Name: Linfeng Zhang
• Email: linfengzh01@gmail.com
• School: UCSD — Computer Science and Engineering (Computer Engineering)
• Interests: System programming, networking, and backend infrastructure