The traditional TCP/IP protocol stack is associated with shortcomings related to the context-switching overhead and redundant data copying. The software-based TOE (TCP/ IP Offload Engine), also known as lightweight TCP/IP, was developed to optimize the TCP/IP protocol stack to run on an embedded system. In this paper, we propose the design of a lightweight TCP/IP protocol stack that runs on an event-driven scheduler. An event-driven scheduler is one of the main components of a real-time operating system that provides essential functionalities for an embedded system in network communication. We discuss the problems involved in designing a lightweight TCP/IP with an eventdriven scheduler, especially for the issues of TCP transmission and TCP retransmission. We implemented and evaluated the proposed TCP/IP stack on an embedded networking device and verified that the proposed TCP/IP stack is well suited for high-performance networking in embedded systems.