Embedded TCP/IP Network Stack

Advanced Dual IPv4 & IPv6 TCP/IP Network Stack

NETX DUO embedded TCP/IP network stack is Express Logic’s advanced, Industrial Grade dual IPv4 and IPv6 TCP/IP network stack designed specifically for deeply embedded, real-time, and IoT applications. NETX DUO provides embedded applications with core network protocols such as IPv4, IPv6, TCP and UDP as well as a complete suite of additional, higher level add-on protocols. NETX DUO is also secure via additional add-on security products, including NETX SECURE IPsec and NETX SECURE SSL/TLS/DTLS. All of this combined with an extremely small footprint, fast execution, and superior ease-of-use make NETX DUO the ideal choice for the most demanding embedded IoT applications.

Cloud Partners


NETX DUO has a remarkably small footprint of 9KB to 15KB for basic IP and UDP support.

An additional 10KB to 13KB of instruction area memory is needed for TCP functionality. NETX DUO RAM usage typically ranges from 2.6KB to 3.6KB plus the packet pool memory, which is defined by the application.

Like THREADX, the size of NETX DUO automatically scales based on the services actually used by the application. This virtually eliminates the need for complicated configuration and build parameters, making things easier for the developer.

Fast execution

NETX DUO provides a zero-copy packet send/receive implementation, highly integrated with THREADX, to achieve the fastest possible performance.

For example, NETX DUO can typically achieve near wirespeed data transfers on an 80MHz (or less) processor, while using only a small percentage of the processor cycles.

Simple, easy-to-use

NETX DUO is very simple to use. The NETX DUO API is both intuitive and highly functional.

The API names are made of real words and not the “alphabet soup” or highly abbreviated names that are so common in other networking products. All NETX DUO APIs have a leading nx_ and follow a noun-verb naming convention. Furthermore, there is a functional consistency throughout the API. For example, all APIs that suspend have an optional timeout that functions in an identical manner for APIs.

For legacy applications, NETX DUO offers an additional BSD socket compatible layer. This layer helps developers migrate large networking applications with ease.

Safe and secure

NETX DUO is secure. This security is provided through additional security products, including IPsec, SSL, TLS, and DTLS.

In addition, the application has complete control over all external access to NETX DUO, making security risk determination that much easier.

Pre-certified by TUV and UL to many safety standards

NETX DUO has been certified by SGS-TUV Saar for use in safety-critical systems, according to IEC-61508 SIL 4, IEC-62304 SW Safety Class C,

ISO 26262 ASIL D and EN 50128. The certification confirms that NETX DUO can be used in the development of safety-related software for the highest safety integrity levels of IEC-61508, IEC-62304, ISO 26262 and EN 50128 for the “Functional Safety of electrical, electronic, and programmable electronic safety-related systems.” SGS-TUV Saar, formed through a joint venture of Germany’s SGS-Group and TUV Saarland, has become the leading accredited, independent company for testing, auditing, verifying and certifying embedded software for safety-related systems worldwide. The industrial safety standard IEC 61508, and all standards that are derived from it, including IEC-62304, ISO 26262 and EN 50128, are used to assure the functional safety of electrical, electronic, and programmable electronic safety-related medical devices, process control systems, industrial machinery, automobiles and railway control systems.


NETX DUO has been recognized by UL for compliance with UL 60730-1 Annex H, CSA E60730-1 Annex H, IEC 60730-1 Annex H, UL 60335-1 Annex R, IEC 60335-1 Annex R, and UL 1998 safety standards for software in programmable components. UL is a global, independent, safety-science company with more than a century of expertise innovating safety solutions, ranging from the public adoption of electricity to breakthroughs in sustainability, renewable energy, and nanotechnology.

Artifacts (Certificate, Safety Manual, Test Report, etc.) associated with the TUV and UL certifications are available for sale. Please contact us for more details at

In cases where the application needs additional certification, a certification service is available through Express Logic for providing turn-key certification to various standards using the actual hardware platform and even covering the application code. Please contact us for more details on our certification service.

EAL4+ Common Criteria security certification

X-WARE IoT PLATFORM SC has achieved EAL4+ Common Criteria security certification. The Target of Evalution (TOE) covers THREADX, NETX DUO, NETX SECURE TLS, and NETX MQTT.

This represents the most typical IoT protocols required by deeply embedded sensors, devices, edge routers, and gateways.

EAL4+ Common Criteria


The IT Security Evaluation Facility used for the X-WARE IoT PLATFORM SC security certification is Brightsight BV and the Certification Authority is SERTIT. Please review this link on SERTIT’s web site for additional details.

FIPS 140-2 Validated

X-WARE IoT PLATFORM NETX™ Crypto libraries have achieved Federal Information Processing Standardization 140-2 (FIPS 140-2) Certification for software, which specifies requirements for cryptography modules.

FIPS 140-2 requires all federal government agencies and departments that use cryptographic-based security to meet specific standards related to encryption strength and capabilities. These cryptographic-based security standards are also recognized in Canada and the European Union.

The Information Security evaluation lab used for X-WARE IoT PLATFORM NETX™ Crypto libraries was atsec and the certification authority is The National Institute of Standards and Technology (NIST). Please review this link on the NIST website for additional details.

Interoperability verification

NETX DUO conforms to RFC standards and offers complete interoperability with devices for most vendors.


NETX DUO is one of the only embedded TCP/IP stacks to achieve the rigorous IPv6-Ready Logo certification, evidence that it has passed conformance and interoperability tests, administered and validated by the IPv6 Forum.

NETX DUO also utilizes the industry standard IxANVL (Automated Network Validation Library) for the NETX DUO core TCP/IP protocol implementation.

Comprehensive IoT solution

NETX DUO has a remarkably small footprint of 9KB to 15KB for basic IP and UDP support.

NETX DUO has one of the most comprehensive TCP/IP networking for deeply embedded IoT applications. This support includes the following add-on protocol products:


Advanced technology

NETX DUO is advanced technology that includes:
  • Piconet™ architecture
  • Automatic scaling
  • UDP Fast-Path Technology™
  • Flexible packet management
  • Zero-copy API and implementation
  • Multihomed support
  • Optional timeout on all suspension
  • Static routing support
  • IPsec
  • TRACEX system analysis support

Fastest time-to-market

NETX DUO is easy to install, learn, use, debug, verify, certify and maintain. As a result,

NETX DUO is one of the most popular TCP/IP stacks for embedded IoT devices, including many SoCs from Broadcom, Gainspan, etc.

Our consistent time-to-market advantage is built on:

  • Quality documentation – please review our NETX DUO User Guide and see for yourself!
  • Complete source code availability
  • Easy-to-use API
  • Comprehensive and advanced feature set

Royalty free

NETX DUO is licensed royalty-free for the lowest possible manufacturing cost.

There are five basic types of licenses, plus the ability to create a custom license for unique situations. Please see the licensing page for more information.

Full, highest-quality source code

From the very beginning, NETX DUO was designed to be an Industrial Grade TCP/IP solution distributed with full

C source code. Throughout the years, NETX DUO source code has set the bar in quality and ease of understanding. In addition, the convention of having one function per file provides for easy source navigation. The following is an example of the NETX DUO nx_icmp_enable.c function:

NETX DUO Source Code

Supports most popular architectures

NETX DUO runs on most popular 32/64-bit microprocessors out-of-the-box, fully tested and fully supported, including the following

advanced architectures:

  • Analog Devices: SHARC, Blackfin, CM4xx
  • Andes Core: RISC-V
  • Ambiqmicro: Apollo MCUs
  • ARM: ARM7, ARM9, ARM11, Cortex-M0/M3/M4/M7/A15/A5/A7/A8/A9/A5x 64-bi/A7x 64-bit/R4/R5, TrustZone ARMv8-M
  • Cadence: Xtensa, Diamond
  • CEVA: PSoC, PSoC 4, PSoC 5, PSoC 6, FM0+, FM3, MF4, WICED WiFi
  • Cypress: RISC-V
  • EnSilica: eSi-RISC
  • Infineon: XMC1000, XMC4000, TriCore
  • Intel & Intel FPGA: x36/Pentium, XScale, NIOS II, Cyclone, Arria 10
  • Microchip: AVR32, ARM7, ARM9, Cortex-M3/M4/M7, SAM3/4/7/9/A/C/D/E/G/L/SV, PIC24/PIC32
  • Microsemi: RISC-V
  • NXP: LPC, ARM7, ARM9, PowerPC, 68K, i.MX, ColdFire, Kinetis Cortex-M3/M4
  • Renesas: SH, HS, V850, RX, RZ, Synergy
  • Silicon Labs: EFM32
  • Synopsys: ARC 600, 700, ARC EM, ARC HS
  • ST: STM32, ARM7, ARM9, Cortex-M3/M4/M7
  • Tl: C5xxx, C6xxx, Stellaris, Sitara, Tiva-C
  • Wave Computing: MIPS32 4K, 24K, 34K, 1004K, MIPS64 5K, microAptiv, interAptiv, proAptiv, M-Class
  • Xilinx: MicroBlaze, PowerPC 405, ZYNQ, ZYNQ UltraSCALE
** Please note that all timing and size figures listed are estimates and may be different on your development platform

Subscribe to our news