lwIP Wiki

lwIP - lightweight TCP/IP

lwIP is a light-weight implementation of the TCP/IP protocol suite that was originally written by Adam Dunkels at the Computer and Networks Architectures (CNA) lab of the Swedish Institute of Computer Science but now is being actively developed by a team of developers distributed world-wide currently administered by Simon Goldschmidt and Dirk Ziegelmeier. The development homepage has the latest news and releases:


lwIP is freely available (under a BSD-style license) in C source code format and can be downloaded from the development homepage.

The focus of the lwIP TCP/IP implementation is to reduce the RAM usage while still having a full scale TCP. This makes lwIP suitable for use in embedded systems with tens of kilobytes of free RAM and room for around 40 kilobytes of code ROM.

Since its release, lwIP has spurred a lot of interest and is today being used in many commercial products. lwIP has been ported to multiple platforms and operating systems and can be run either with or without an underlying OS.

lwIP includes the following protocols and features:

  • IP (Internet Protocol) including packet forwarding over multiple network interfaces
  • ICMP (Internet Control Message Protocol) for network maintenance and debugging
  • IGMP (Internet Group Management Protocol) for multicast traffic management
  • UDP (User Datagram Protocol) including experimental UDP-lite extensions
  • TCP (Transmission Control Protocol) with congestion control, RTT estimation and fast recovery/fast retransmit
  • Raw/native API for enhanced performance
  • Optional Berkeley-like socket API
  • DNS (Domain names resolver)
  • SNMP (Simple Network Management Protocol)
  • DHCP (Dynamic Host Configuration Protocol)
  • AUTOIP (for IPv4, conform with RFC 3927)
  • PPP (Point-to-Point Protocol)
  • ARP (Address Resolution Protocol) for Ethernet

Getting started

If you are new to lwIP, we recommend that you read one of the following manuals:

The following links may also be useful:

Further reading