SCTP_NAPI

Opinionated native Node.js addon for SCTP SEQPACKET sockets. Provides a single open() call that returns a handle with send() and close() methods, with event-driven receive via libuv.

System requirements

Linux only. SCTP is a kernel protocol — this addon links against libsctp and requires the kernel module loaded.

1. Install lksctp-tools

This provides the libsctp.so shared library and /usr/include/netinet/sctp.h header.

Arch Linux:

sudo pacman -S lksctp-tools

Fedora / RHEL:

sudo dnf install lksctp-tools-devel

2. Load the kernel module

The SCTP kernel module must be loaded. It usually auto-loads on first use, but to be explicit:

sudo modprobe sctp

3. Build tools

node-gyp compiles the C addon. It needs Python 3, make, and a C compiler:

# Arch
sudo pacman -S base-devel python

# Debian / Ubuntu
sudo apt install build-essential python3

Setup

pnpm install
pnpx node-gyp rebuild

pnpm install pulls in the node-gyp dependency. node-gyp rebuild compiles sctp_dgram.c into build/Release/sctp_dgram.node.

API

The addon exports a single function:

const sctp = require("./build/Release/sctp_dgram.node");

const handle = sctp.open(bindHost, bindPort, recvMaxlen, onRecv);

sctp.open(bindHost, bindPort, recvMaxlen, onRecv)

Creates an SCTP SEQPACKET socket, binds it, and starts listening for incoming messages. Returns a handle object.

• bindHost string — IP to bind to ("0.0.0.0" for all interfaces)
• bindPort number — port to bind to (0 for ephemeral)
• recvMaxlen number — max bytes per received message (pre-allocated buffer)
• onRecv (result: [Buffer, string, number] | string) => void — called on each received message. result is [data, host, port], or an error string on failure.

The socket is created with these options hardcoded:

• SOCK_NONBLOCK — non-blocking I/O
• SO_REUSEADDR — allow port reuse
• SCTP_NODELAY — disable Nagle's algorithm
• SCTP_RTOINFO — retransmission tuned for LAN (initial=250ms, min=200ms, max=5000ms)
• SCTP_RECVRCVINFO — enables receive info on incoming messages
• IPv6 dual-stack with IPV6_V6ONLY=0 when binding to IPv6
• Sends use SCTP_UNORDERED flag and PR-SCTP TTL of 30s

handle.send(buffer, host, port)

Send a message to the given address. Returns bytes sent.

• buffer Buffer — data to send
• host string — destination IP
• port number — destination port

handle.close()

Stops receiving, closes the socket, and frees resources. Safe to call multiple times. If not called explicitly, the GC finalizer will clean up.

Internals

Receive is event-driven via uv_poll_t on the socket fd, integrated into Node's event loop. When the fd becomes readable, the C callback drains up to 64 messages per tick (preventing event loop starvation), then yields. Each received message is copied into a JS-owned Buffer and delivered via the callback.