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This guide provides a reference for developers and engineers porting the wolfSSL lightweight SSL/TLS library to new embedded platforms, operating systems, or transport mediums (TCP/IP, bluetooth, etc). It calls out areas in the wolfSSL codebase which typically require modification when porting wolfSSL. It should be considered a guide and as such, it is an evolving work. If there is something you find missing, please let us know and we’ll be happy to add instructions or clarification to the document.


This guide caters to developers or engineers porting the wolfSSL and wolfCrypt to new platforms or environments that are not supported by default.


Several steps need to be iterated through when getting wolfSSL to run on an embedded platform. Some of these steps are outlined in Section 2.4 of the wolfSSL Manual.

Apart from steps in Chapter 2 of the wolfSSL Manual, there are areas in the code which may need porting or modifications in order to accommodate a specific platform. wolfSSL abstracts many of these areas, attempting to make it as easy as possible to port wolfSSL to a new platform.

In the ./wolfssl/wolfcrypt/settings.h file, there are several defines specific to different operating systems, TCP/IP stacks, and chipsets (ie: MBED, FREESCALE_MQX, MICROCHIP_PIC32, MICRIUM, EBSNET, etc). There are two main locations to put #defines when compiling and porting wolfSSL to a new platform:

First, new defines for a Operating System or TCP/IP stack port are typically added to the settings.h file when a new port of wolfSSL is completed. This provides an easy way to turn on/off features as well as customize build settings that should be default for that build. New custom defines can be added in this file when doing a port of wolfSSL to a new platform. We encourage users to contribute ports of wolfSSL back to the master open source code branch on GitHub. This helps keep wolfSSL up to date and allows different ports to remain updated as the wolfSSL project improves and moves forward.

For users not wanting to contribute back their changes to wolfSSL proper, or for users who want to customize the wolfSSL build with additional preprocessor defines, wolfSSL recommends the use of a custom "user_settings.h" header file. If WOLFSSL_USER_SETTINGS is defined when compiling the wolfSSL source files, wolfSSL will automatically include a custom header file called "user_settings.h". This header should be created by the user and placed on the include path. This allows users to maintain one single file for their wolfSSL build, and makes it much easier to update to newer versions of wolfSSL.

wolfSSL encourages the submission of patches and code changes through either direct email (, or through GitHub pull request.