A TCP Echo Client Example (using a single RTOS task)
FreeRTOS+TCP and FreeRTOS+FAT Examples

Not all demo projects will include this example. If this example is included in a demo project then it may be necessary to set mainCREATE_TCP_ECHO_TASKS_SINGLE to 1 at the top of the project's main.c source file to include the example in the build.

The example creates two RTOS tasks that send TCP echo requests to an external echo server using the standard echo port (port 7), then wait to receive the echo reply within the same RTOS task. A separate TCP echo example uses the same TCP socket from two different RTOS tasks - one RTOS task sends the echo request and another RTOS tasks receives the echo reply.

The IP address of the echo server must be configured using the configECHO_SERVER_ADDR0 to configECHO_SERVER_ADDR3 constants in FreeRTOSConfig.h, and the echo server must (stating the obvious) be enabled and not blocked by a firewall. Windows ships with an echo server but it is not enabled by default. Third party echo servers are also available.