Module @ndn/node-transport


This package is part of NDNts, Named Data Networking libraries for the modern web.

This package implements socket transports for Node.js environment.

import { TcpTransport, UdpTransport, UnixTransport } from "@ndn/node-transport";

// other imports for examples
import { FwPacket } from "@ndn/fw";
import { type Transport, L3Face } from "@ndn/l3face";
import { Data, Interest } from "@ndn/packet";
import { delay } from "@ndn/util";

if (process.env.CI) { process.exit(0); }

Transport Types

There are three transport types:

  • UnixTransport: Unix socket or Windows named pipe.
  • TcpTransport: TCP tunnel (IPv4 or IPv6).
  • UdpTransport: UDP unicast tunnel (IPv4 or IPv6) or UDP multicast group (IPv4 only).

The connect() function of each transport creates a transport.

// NOTICE: ndnts-demo-* hostnames are not intended for general application use.

// UnixTransport.connect() establishes a UNIX socket connection.
// It accepts a Unix socket path.
try {
const unix = await UnixTransport.connect(process.env.DEMO_NFD_UNIX ?? "/run/nfd/nfd.sock");
await useInL3Face(unix);
} catch (err: unknown) { // NFD is not running
console.warn("unix", err);

// TcpTransport.connect() establishes a TCP tunnel.
// It accepts either host+port or an options object for net.connect().
try {
const tcp4 = await TcpTransport.connect("", 6363);
await useInL3Face(tcp4);
} catch (err: unknown) { // router unavailable
console.warn("tcp4", err);

// Select IPv4 with `family: 4` or select IPv6 with `family: 6`. Default is both.
try {
const tcp6 = await TcpTransport.connect({ host: "", family: 6 });
await useInL3Face(tcp6);
} catch (err: unknown) { // router unavailable
console.warn("tcp6", err);

// UdpTransport.connect() establishes a UDP tunnel.
try {
const udp4 = await UdpTransport.connect("");
await useInL3Face(udp4);
} catch (err: unknown) { // router unavailable
console.warn("udp4", err);

// Select IPv6 with `family: 6`. Default is IPv4 only, unless host is a literal IPv6 address.
try {
const udp6 = await UdpTransport.connect({ host: "", family: 6 });
await useInL3Face(udp6);
} catch (err: unknown) { // router unavailable
console.warn("udp6", err);

To use UDP multicast, each network interface needs to have a separate transport. It's easiest to let NDNts automatically create transports on every network interface.

// UdpTransport.multicasts() attempts to create UDP multicast transports on every
// network interface, skipping network interfaces where socket creation fails.
const multicasts = await UdpTransport.multicasts();
for (const transport of multicasts) {
await useInL3Face(transport);

How to Use a Transport

Transports are normally used to construct L3Face objects (from @ndn/l3face package), which are in turn added to the Forwarder (from @ndn/fw package). Each transport provides a createFace convenience function to construct a transport and add it to the forwarder.

See @ndn/ws-transport package documentation for a complete example of createFace function.

// UdpTransport.createFace() constructs a UDP unicast transport, and adds it to a forwarder.
// First parameters allows setting L3Face attributes and NDNLP service options, or attaching
// the face to a non-default Forwarder instance. This argument is required.
// Subsequent parameters are same as the corresponding connect() function.
// It returns a FwFace instance (from @ndn/fw package).
const face = await UdpTransport.createFace({}, "");
// TcpTransport.createFace() and UnixTransport.createFace() behave similarly.

// UdpTransport.createMulticastFaces() constructs UDP multicast transports on every network
// interface and adds them to a forwarder.
const faces = await UdpTransport.createMulticastFaces({});
for (const face of faces) {

L3Face Low-Level Details

L3Face allows sending and receiving layer-3 packets on a transport. L3Face does not provide Interest-Data matching logic, timeout scheduler, etc. It is more like a forwarder's face.

This section presents the low-level details of how to use a "raw" transport with L3Face class.

async function useInL3Face(transport: Transport) {

// Transports are normally used in a network layer face.
const face = new L3Face(transport);

// We want to know if something goes wrong.
face.addEventListener("rxerror", (evt) => console.warn(evt.detail));
face.addEventListener("txerror", (evt) => console.warn(evt.detail));

await Promise.all([
face.tx({ async *[Symbol.asyncIterator]() {
// Send five Interests.
let seq = Math.trunc(Math.random() * 1e8);
for (let i = 0; i < 5; ++i) {
await delay(50);
const interest = new Interest(`/ndn/edu/memphis/ping/NDNts/${seq++}`);
console.log(`${transport} <I ${}`);
yield FwPacket.create(interest);
await delay(500);
} }),
(async () => {
let nData = 0;
for await (const { l3 } of face.rx) {
if (!(l3 instanceof Data)) {
// Print incoming Data name.
console.log(`${transport} >D ${}`);
if (++nData >= 5) {

// L3Face and Transport are automatically closed when TX iterable is exhausted.