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Wireless Network Interface Daemon for Low-Power Wireless SoCs

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wpantund, Userspace WPAN Network Daemon

is a user-space network interface driver/daemon that provides a native IPv6 network interface to a low-power wireless Network Co-Processor (or NCP). It was written and developed by Nest Labs to make supporting Thread connectivity on Unix-like operating systems more straightforward.

is designed to marshall all access to the NCP, ensuring that it always remains in a consistent and well-defined state.

This is not an official Google product.

Feature and Architecture Summary

  • ... a native IPv6 interface to an NCP.
  • ... a command line interface (
    ) for managing and configuring the NCP.
  • ... a DBus API for managing and configuring the NCP.
  • ... a way to reliably manage the power state of the NCP.
  • ... a uniform mechanism for handling NCP firmware updates.

The architecture and design of

has been motivated by the following design goals (in no specific order):
  • Portability across Unix-like operating systems (currently supports Linux. BSD support should be fairly trivial to add)
  • Require few runtime dependencies (DBus, with boost needed when building)
  • Single-threaded architecture, with heavy use of asynchronous I/O
  • Power efficiency (0% CPU usage when idle)
  • Allow management interface to be used by multiple independent applications simultaneously
  • Allow multiple instances of
    to gracefully co-exist on a single machine
  • Modular, plugin-based architecture (all details for communicating with a specific NCP stack are implemented as plugins)

Note that Windows is not currently supported, but patches are welcome.

The following NCP plugins are provided:

  • src/ncp-spinel
    : Supports NCPs that communicate using the Spinel NCP Protocol, used by NCPs running OpenThread
  • src/ncp-dummy
    : A dummy NCP plug-in implementation meant to be the starting point for implementing new NCP plug-ins


is open-source software released under the Apache License, Version 2.0. See the file
for more information.

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

Conceptual Overview

is conceptually similar in purpose to the point-to-point daemon (
, commonly used on Unix platforms to provide network connectivity via a dial-up modems) except that instead of communicating with a dial-up modem,
is communicating with an NCP.

communicates with the NCP via an abstraction of a asynchronous stream socket, which could be any of the following:
  • A real serial port (UART) connected to the NCP (preferably with hardware flow control)
  • The stdin and stdout from a subprocess (for supporting SPI interfaces using a translator program or debugging virtual stacks)
  • A TCP socket (for debugging, not recommended for production)

Unlike a dial-up modem, NCPs often have a rich management interface for performing operations, such as forming a network, joining a network, scanning for nearby networks, etc. To perform these operations,

includes a command line utility called
. Applications that need to directly configure the network interface can also communicate directly with
using its DBus API.

To expose a native IPv6 network interface to the host operating system,

uses the
driver on Linux. On Linux, the default name for the interface is

Usage Overview

The behavior of

is determined by its configuration parameters, which may be specified in a configuration file (typically
) or at the command line. A typical configuration file might look like that shown below. For a more thorough explanation of available configuration parameters, see the included example.
# Try to name the network interface `wpan0`.
# If not possible, a different name will be used.
Config:TUN:InterfaceName      "wpan0"

The pathname of the socket used to communicate

with the NCP.

Config:NCP:SocketPath "/dev/ttyUSB0"

The name of the driver plugin to use. The chosen

plugin must support the NCP you are trying to use.

Config:NCP:DriverName "spinel"

Drop root privileges after opening all sockets

Config:Daemon:PrivDropToUser "nobody"

Use a CCA Threshold of -70db

NCP:CCAThreshold "-70"

When up and running, you can use

to check the status of the interface and perform various management operations. For example, to check the general status of an interface:
$ sudo wpanctl status
wpan0 => [
    "NCP:State" => "offline"
    "Daemon:Enabled" => true
    "NCP:Version" => "OPENTHREAD/g1651a47; May 23 2016 17:23:24"
    "Daemon:Version" => "0.07.00 (May 23 2016 12:58:54)"
    "Config:NCP:DriverName" => "spinel"
    "NCP:HardwareAddress" => [F1D92A82C8D8FE43]

Here we see that the NCP is in the

state along with a few additional bits of information such as the version of the NCP and its hardware address. From here we can easily form a new network:
$ sudo wpanctl form "wpantund-testnet"
Forming WPAN "wpantund-testnet" as node type router
Successfully formed!

Now if we check the status, we will see more information:

$ sudo wpanctl status
wpan0 => [
    "NCP:State" => "associated"
    "Daemon:Enabled" => true
    "NCP:Version" => "OPENTHREAD/g1651a47; May 23 2016 17:23:24"
    "Daemon:Version" => "0.07.00 (May 23 2016 12:58:54)"
    "Config:NCP:DriverName" => "spinel"
    "NCP:HardwareAddress" => [F1D92A82C8D8FE43]
    "NCP:Channel" => 23
    "Network:NodeType" => "leader"
    "Network:Name" => "wpantund-testnet"
    "Network:XPANID" => 0x09717AEF221F66FB
    "Network:PANID" => 0xBFCD
    "IPv6:LinkLocalAddress" => "fe80::f3d9:2a82:c8d8:fe43"
    "IPv6:MeshLocalAddress" => "fd09:717a:ef22::9a5d:5d1e:5527:5fc8"
    "IPv6:MeshLocalPrefix" => "fd09:717a:ef22::/64"
$ ifconfig wpan0
wpan0: flags=8051 mtu 1280
    inet6 fe80::f3d9:2a82:c8d8:fe43%wpan0 prefixlen 10 scopeid 0x15
    inet6 fd09:717a:ef22::9a5d:5d1e:5527:5fc8 prefixlen 64

If compiled with

supports an convenient interactive console. All commands support online help: type
to get a list of supported commands, or add
to a command to get help with that specific command.

For simulation example Codelab please see:


Submit bugs and feature requests to issue tracker. We use the following mailing lists for discussion and announcements:

Authors and Contributors

The following people have significantly contributed to the design and development of

  • Robert Quattlebaum
  • Marcin Szczodrak
  • Vaas Krishnamurthy
  • Arjuna Siva
  • Abtin Keshavarzian

If you would like to contribute to this project, please read first.

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