As the essential component responsible for communication, network services are security-critical, and it is vital to find v u lnerabilities i n t h em. F u zzing i s c u rrently o n e o f the most popular software vulnerability discovery techniques, widely adopted due to its high efficiency and low false positives. However, existing coverage-guided fuzzers mainly aim at stateless local applications, leaving stateful network services underexplored. Recently, some fuzzers targeting network services have been proposed but have certain limitations, e.g., insufficient o r inaccurate state representation and low testing efficiency.In this paper, we propose a new fuzzing solution NSFuzz for stateful network services. Specifically, w e s t udied t y pical implementations of network service programs and figured o u t how they represent states and interact with clients, and accordingly propose (1) a program variable-based state representation scheme and (2) an efficient i n teraction s y nchronization m e chanism to improve efficiency. We have implemented a prototype of NSFuzz, which uses static analysis to identify network event loops and extract state variables, then achieves fast I/O synchronization and efficient s t ate-aware f u zzing v i a l i ghtweight compile-time instrumentation. The preliminary evaluation results show that, compared with state-of-the-art network service fuzzers AFLNET and STATEAFL, our solution NSFuzz could infer a more accurate state model during fuzzing and improve the testing throughput by up to 50x and the coverage by up to 20%.