Hello Vishakha,
There are two examples in the LPCOpen folder within the MCUXpresso IDE.
Both are examples containing lwip one uses Free-RTOS and the other is a stand alone example(without an RTOS).
MCUXpresso is an eclipse-based IDE. You download it from here.
Once downloaded you can follow this path in your computer to find the LPCOpen folder which contains many examples from different microcontrollers, including the LPC1769.
C:\nxp\MCUXpressoIDE_11.0.0_2516\ide\Examples\LPCOpen
Inside the folder you will find several examples using different peripherals. However the two that may interest you are named:
lwip_tcpecho_freertos
lwip_tcpecho_sa
Let me know if you have any questions.
Best Regards,
Sabina