PyTCP 3.0.5

Pure-Python, zero-dependency TCP/IP stack — Ethernet through RFC 9293 TCP — running in user space on a TAP/TUN interface, with a Berkeley-sockets API.

PyTCP

Pure-Python, zero-dependency TCP/IP stack — Ethernet through RFC 9293 TCP — running in user space on a TAP/TUN interface, with a Berkeley-sockets API.

from pytcp import socket, stack

What it is

A full, RFC-grounded TCP/IP stack implemented entirely in Python: Ethernet II / 802.3, ARP, IPv4 / IPv6 (with extension headers), ICMPv4 / ICMPv6 (incl. Neighbor Discovery, MLDv2), UDP, and a RFC 9293 TCP with a real FSM, congestion control, and a BSD-sockets facade. It runs on a TAP/TUN interface in user space — no kernel module, no privileged data path.

Architecture

The stack is split into three independently-published, strictly-layered distributions:

Distribution	Import	Role
PyTCP-net_addr	net_addr	Address value types (IPv4/IPv6/MAC, networks, masks).
PyTCP-net_proto	net_proto	Protocol packet parse / assemble / validate.
PyTCP	pytcp	The running stack: threads, sockets, ARP/ND caches, RX/TX rings.

Installing PyTCP pulls the other two automatically (lockstep version pin).

Install

pip install PyTCP

Brings in PyTCP-net_proto and PyTCP-net_addr (and aenum). Fully typed (ships py.typed, PEP 561).

Requirements

Python 3.14+, Linux (TAP/TUN), POSIX. Running the stack needs a TAP/TUN interface (root for interface/bridge setup).

License

GPL-3.0-or-later. PyTCP by Sebastian Majewski.