CycloneTCP is a dual IPv4/IPv6 stack dedicated to embedded applications. CycloneTCP conforms to RFC standards and offers seamless interoperability with existing TCP/IP systems. By supporting IPv6, CycloneTCP eases deployment of next-generation Internet. The stack is distributed as a full ANSI C and highly maintainable source code.

• Built-in support for multiple network interfaces
• BSD style socket API
• Blocking/non-blocking socket operation and event-driven functions (select and poll)
• Efficient data transfer through zero copy
• Well-crafted TCP module with selective ACK and congestion control
• Raw socket interface
• Multicast support (IGMPv2 and MLDv1)
• IP fragmentation and reassembly support
• Flexible memory footprint
• High throughput
• Dialog-based configuration wizard
• Portable architecture (no processor dependencies)
• Straightforward port to any RTOS
• Debugging and trace functionality to ease development and integration
• Host name resolution (DNS, mDNS and NetBIOS Name Service)
• mDNS and NetBIOS responder
• DNS-based service discovery (DNS-SD)
• Auto-IP (dynamic configuration of IPv4 link-local addresses)
• DHCP client and DHCP server
• SLAAC (IPv6 stateless address autoconfiguration )
• DHCPv6 client and DHCPv6 relay agent
• FTP / FTPS client (implicit TLS and explicit TLS modes supported)
• FTP / FTPS server (implicit TLS and explicit TLS modes supported)
• HTTP / HTTPS client
• HTTP / HTTPS server with SSI, CGI scripting and WebSocket support
• HTTP/2 client (including HPACK compression, server push and https scheme)
• MQTT v3.1.1 client (TCP, TLS, WebSocket and secure WebSocket transport layers supported)
• MQTT-SN client (UDP and DTLS transport layers supported)
• CoAP client (DTLS-secured CoAP, Observe and Block-Wise Transfers supported)
• SMTP client
• Network time synchronization (SNTP client)
• SNMPv1/SNMPv2c/SNMPv3 agent (MD5/SHA-1 authentication and DES/AES privacy protocols are supported)
• Remote management of SNMP users and access rights (SNMP-USM-MIB and SNMP-VACM-MIB)
• Standard MIBs: MIB-II, IF-MIB, IP-MIB, TCP-MIB, UDP-MIB, SNMPv2-MIB
• TFTP client and TFTP server
• Secure Modbus/TCP client (TCP and TLS transport layers supported)
• Secure Modbus/TCP server (TCP and TLS transport layers supported)
• WebSockets client and server API (WebSocket connections tunneled over SSL/TLS supported)
• VLAN support (802.1q and 802.1ad)
• Support for virtual interfaces (multiple MAC addresses per physical interface)
• Support for multi-homed hosts and IP aliasing (multiple IPv4 addresses per interface)
• Ethernet port multiplication using VLAN tagging (SMSC switches) or tail tagging (Micrel switches)
• PPP (Point-to-Point Protocol)
• USB/RNDIS driver (for STM32 microcontrollers)

CycloneTCP can run in a bare metal environment (without any RTOS). CycloneTCP also supports major open source and commercial RTOS:

• Amazon FreeRTOS
• ChibiOS/RT
• CMSIS-RTOS
• CMSIS-RTOS2 (RTX v5 and FreeRTOS)
• Keil RTX
• Micrium µC/OS-II
• Micrium µC/OS-III
• Segger embOS
• SYS/BIOS (TI-RTOS)

CycloneTCP User's Manual (Restricted access)

Try out CycloneTCP now! By clicking the following link, you will access a real Web server that runs FreeRTOS + CycloneTCP Open on a Cortex-M3 microcontroller (STM3220G-EVAL demonstration board from STMicroelectronics).

Online Demo

The TCP/IP stack is available either as open source (CycloneTCP Open) or under a commercial license (CycloneTCP Lite, Pro or Ultimate) for proprietary developments in a commercial context.

Product Licensing

CycloneTCP Open (GPLv2 license) and CycloneTCP Eval (time-limited evaluation license) are available for download. If you want to browse the source tree instead of downloading, the complete source code and documentation are also available online.

Download Source Code
Browse Source Code and Documentation