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QNX Software Development Platform
QNX SDP is a cross-compiling and debugging environment, including an IDE and command-line tools, for building binary images and programs for target boards running the QNX OS 8.0.
OS Components & Operations
High-Performance Networking Stack (io-sock) User's Guide
This guide contains instructions for implementing and using the QNX OS High-Performance Networking Stack and its manager, io-sock.
Overview
Threading model and priorities

QNX Momentics IDE User's Guide
This User's Guide describes version 8.0 of the Integrated Development Environment (IDE) that's part of the QNX Tool Suite.
QNX Software Development Platform
QNX SDP is a cross-compiling and debugging environment, including an IDE and command-line tools, for building binary images and programs for target boards running the QNX OS 8.0.
- Quickstart Guide
- System Architecture
  The System Architecture guide accompanies the QNX OS and is intended for both application developers and end-users.
- OS Components & Operations
  - Boot Optimization Guide
    The Boot Optimization Guide describes techniques you can use to reduce the time from your board's initial power on until you have a fully functional QNX system running on the board.
  - Building Embedded Systems
    The Building Embedded Systems guide is intended for developers who are developing or building BSPs for QNX OS embedded systems.
  - Customizing a BSP
    While QNX provides Board Support Packages (BSPs) for many common platforms and their individual variants, in some cases, you need a BSP for a board that QNX does not provide. If this is the case, you can modify a QNX BSP or develop your own.
  - Device Publishers Developer's Guide
  - High Availability Framework Developer's Guide
  - High-Performance Networking Stack (io-sock) User's Guide
    This guide contains instructions for implementing and using the QNX OS High-Performance Networking Stack and its manager, io-sock.
    - Overview
      - Architecture of io-sock
        The io-sock network stack is very similar in architecture to other component subsystems inside of the QNX OS.
      - Threading model and priorities
      - Socket API
        The BSD Socket API is the standard API for TCP/IP programming in the UNIX world. In the Windows world, the Winsock API is based on and shares a lot with the BSD Socket API. This makes conversion between the two fairly easy.
      - WiFi capability
    - Privilege Control
      Like other components that run on QNX OS, the privileged operations required by io-sock and networking components are protected by process manager abilities. These abilities are configured either directly by the components themselves, or, preferably, via security policies that are defined by the system integrator.
    - Packet Filtering
    - Starting io-sock and Driver Management
    - Running io-sock with Diagnostic Features
    - Networking Services
      The io-sock networking stack provides services ported from FreeBSD.
    - Protocols
      The io-sock networking stack provides Internet protocols ported from FreeBSD.
    - Networking APIs
    - Networking Utilities
    - Writing Network Drivers for io-sock
    - A Hardware-Independent Sample Driver
    - Adding PTP to io-sock Network Drivers
      This appendix describes how to add 2-Step Precision Time Protocol (PTP) Ethernet packet timestamping functionality to an io-sock driver.
    - Writing an io-sock Module
    - PTP Module Library API
      These PTP module functions are implemented by the PTP module. Networking drivers use them to handle actions such as transmit (Tx) and receive (Rx) timestamping and handing off PTP I/O-command (ioctl()) command processing.
  - PCI Server User's Guide
  - Performance Tuning User's Guide
  - QNX Filesystem for Safety User's Guide
  - SMMUMAN User's Guide
  - System Analysis Toolkit (SAT) User's Guide
  - Technotes
  - User's Guide
    The QNX OS User's Guide is intended for all users of a QNX OS system, from system administrators to end users.
- Graphics
- Programming
- System Security Guide
  The QNX System Security Guide is intended for both system integrators who are responsible for the security of a QNX OS system and developers who want to create a QNX OS resource manager free from vulnerabilities.
- Utilities & Libraries
- Migrating to QNX OS 8.0
QNX Software in the Cloud
QNX Software in the Cloud enables developers to use the QNX OS in the Amazon cloud environment.
QNX Toolkit for Visual Studio Code
This User's Guide describes the QNX^® Toolkit for Visual Studio Code. The guide introduces you to the QNX Toolkit by explaining the QNX development environment and how to build, run, and debug your QNX^® Operating System (OS) applications and systems.
QNX Hypervisor User's Guide
This User's Guide explains the QNX hypervisor architecture and provides instructions for installing and running a QNX Hypervisor system, changing system components and configuration, and using hypervisor features such as virtual devices (vdevs).
Typographical Conventions, Support, and Licensing
This section describes the typographical conventions used throughout the documentation, explains how to obtain technical support, and provides some information about licensing.

Threading model and priorities

QNX SDP8.0High-Performance Networking Stack (io-sock) User's GuideAPIArchitecture

The default mode of operation for io-sock is to start with multiple threads for:

the stack
each CPU
resource managers on each CPU

In addition, each driver creates one (e.g., devs-re.so) or several (e.g., devs-ix.so) threads per CPU.

Configuring thread priority

The threading model for io-sock combines the FreeBSD kernel and a QNX resource manager.

Note:

If io-sock runs out of threads, it blocks. There is a limit of 700 resource manager threads and 1000 total threads.

The io-sock manager allows you to configure thread priority. The default priority is 21. For information on setting the priority using an io-sock configuration file, see the io-sock and sysctl entries in the Utilities Reference.

Driver-specific thread priorities are not supported.

Page updated: August 11, 2025