nex

Cross-platform low-level networking library in Rust

Overview

nex is a Rust library that provides cross-platform low-level networking capabilities.
It includes sub-crates with responsibilities:

• nex-packet: Low-level packet parsing and serialization.
• nex-datalink: Raw datalink send/receive backends across platforms.
• nex-socket: Low-level socket operations with cross-platform option handling.

The project aims to expose portable low-level primitives.

Minimum Supported Rust Version

nex requires Rust 1.88.0 or later. MSRV changes are treated as compatibility changes and are verified in CI.

Usage

To use nex, add it as a dependency in your Cargo.toml:

[dependencies]
nex = "0.28"

Using Specific Sub-crates

You can also directly use specific sub-crates by importing them individually.

• nex-datalink
• nex-packet
• nex-socket

If you want to focus on network interfaces, you can use the netdev.

Features

All optional features are disabled by default in nex, nex-packet, nex-datalink, and nex-socket. nex-core keeps gateway enabled by default because gateway discovery is part of its primary interface functionality.

Feature	Crate	Purpose
async	nex, nex-datalink, nex-socket	Enables asynchronous datalink I/O and Tokio-based socket APIs.
pcap	nex, nex-datalink	Enables the libpcap backend.
winptap	nex, nex-datalink	Enables an explicitly selected receive-only Windows Packet Monitor backend without Npcap; combine with async for asynchronous reception.
serde	nex, nex-core, nex-packet, nex-datalink	Enables serialization support for public data types.
gateway	nex-core	Enables default gateway discovery through netdev.

To use asynchronous APIs through the facade:

[dependencies]
nex = { version = "0.28", features = ["async"] }

Privileges

nex-datalink uses a raw socket which may require elevated privileges depending on your system's configuration.
Execute with administrator privileges if necessary.

For Windows Users

For receive-only Ethernet capture without Npcap, enable winptap and call nex::datalink::winptap::open with its dedicated configuration. This requires administrator privileges and does not support transmission or promiscuous mode. With both winptap and async, winptap::open_async returns a runtime-independent AsyncRawReceiver/Stream with a bounded handoff and cross-thread cancellation. The official backend observes incoming and outgoing traffic; native observes incoming traffic only.

Please note that in order to send and receive raw packets using nex-datalink on Windows, Npcap is required.

1. Install Npcap, making sure to check Install Npcap in WinPcap API-compatible Mode during the installation.

2. The default datalink backend loads Npcap at runtime and does not require the Npcap SDK to build. If you enable the optional pcap feature, download the Npcap SDK and add its Lib/x64 (or Lib for 32-bit builds) folder to your LIB environment variable.

For macOS Users

On macOS, managing access to the Berkeley Packet Filter (BPF) devices is necessary to send and receive raw packets using nex-datalink. You can use chmod-bpf to automatically manage permissions for BPF devices. Alternatively, of course, you can also use sudo to temporarily grant the necessary permissions.