# Porting a TCP/IP stack
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This section provides instruction for porting and testing on-board TCP/IP stacks. If your platform offloads TCP/IP and TLS functionality to a separate network processor or module, you can skip this porting section and visit [Porting the Network Transport Interface](afr-porting-network-transport-interface.md).

[FreeRTOS\+TCP](https://www.freertos.org/FreeRTOS-Plus/FreeRTOS_Plus_TCP/index.html) is a native TCP/IP stack for the FreeRTOS kernel. FreeRTOS\+TCP is developed and maintained by the FreeRTOS engineering team and is the recommended TCP/IP stack to use with FreeRTOS. For more information, see [Porting FreeRTOS\+TCP](#porting-freertos-tcp). Alternatively, you can use the third-party TCP/IP stack [lwIP](https://savannah.nongnu.org/projects/lwip/) . The testing instruction provided in this section uses the transport interface tests for TCP plain text, and is not dependent on the specific implemented TCP/IP stack. 

## Porting FreeRTOS\+TCP
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FreeRTOS\+TCP is a native TCP/IP stack for the FreeRTOS kernel. For more information, see [FreeRTOS.org](https://www.freertos.org/FreeRTOS-Plus/FreeRTOS_Plus_TCP/).

### Prerequisites
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To port the FreeRTOS\+TCP library, you need the following:
+ An IDE project that includes the vendor-supplied Ethernet or Wi-Fi drivers.

  For information about setting up a test project, see [Setting up your workspace and project for porting](porting-set-up-project.md).
+ A validated configuration of the FreeRTOS kernel.

  For information about configuring the FreeRTOS kernel for your platform, see [Configuring a FreeRTOS kernel port](afr-porting-kernel.md).

### Porting
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Before you start porting the FreeRTOS\+TCP library, check the [GitHub](https://github.com/FreeRTOS/FreeRTOS-Plus-TCP/tree/main/source/portable/NetworkInterface) directory to see if a port to your board already exists.

If a port does not exist, do the following:

1. Follow the [Porting FreeRTOS\+TCP to a Different Microcontroller](https://www.freertos.org/FreeRTOS-Plus/FreeRTOS_Plus_TCP/Embedded_Ethernet_Porting.html) instructions on FreeRTOS.org to port FreeRTOS\+TCP to your device.

1. If necessary, follow the [Porting FreeRTOS\+TCP to a New Embedded C Compiler](https://www.freertos.org/FreeRTOS-Plus/FreeRTOS_Plus_TCP/Embedded_Compiler_Porting.html) instructions on FreeRTOS.org to port FreeRTOS\+TCP to a new compiler.

1. Implement a new port that uses the vendor-supplied Ethernet or Wi-Fi drivers in a file called `NetworkInterface.c`. Visit the [GitHub](https://github.com/FreeRTOS/FreeRTOS-Plus-TCP/tree/main/source/portable/NetworkInterface/board_family) repository for a template.

After you create a port, or if a port already exists, create `FreeRTOSIPConfig.h`, and edit the configuration options so they are correct for your platform. For more information about the configuration options, see [FreeRTOS\+TCP Configuration](https://www.freertos.org/FreeRTOS-Plus/FreeRTOS_Plus_TCP/TCP_IP_Configuration.html) on FreeRTOS.org.

## Testing
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Whether you use FreeRTOS\+TCP library or a third party library, follow the steps below for testing:
+ Provide an implementation for `connect/disconnect/send/receive` APIs in transport interface tests.
+ Setup an echo server in plain text TCP connection mode, and run transport interface tests.

**Note**  
To officially qualify a device for FreeRTOS, if your architecture requires to port a TCP/IP software stack, you need to validate the device's ported source code against transport interface tests in plain text TCP connection mode with AWS IoT Device Tester. Follow the instructions in [Using AWS IoT Device Tester for FreeRTOS](https://docs.aws.amazon.com/freertos/latest/userguide/device-tester-for-freertos-ug.html) in the *FreeRTOS User Guide* to set up AWS IoT Device Tester for port validation. To test a specific library's port, the correct test group must be enabled in the `device.json` file in the Device Tester `configs` folder.