In this paper, we introduce a passivity-based design framework for event-triggered networked control systems. We consider the effects of network-induced time delays, signal quantization, and data loss in communication links between the plant and controller and show L-2-stability and robustness for the control design. We introduce simple asynchronous triggering conditions that do not rely on the exact knowledge of the systems' dynamics and are located on both sides of the communication network. This leads to a great decrease in the communication rate between systems. Additionally, we show lower bounds on interevent time intervals for the triggering conditions and characterize the design's robustness against external disturbances. We illustrate the relationship among stability, robustness, and passivity levels of the plant and controller. Moreover, we analyze our design's robustness against packet dropouts. Finally, we calculate the passivity levels for the entire event-triggered networked control system. This is beneficial in design of compositional networked control systems. Our results are design-oriented. By following our proposed framework, the designer can characterize clear tradeoffs among passivity levels, design parameters, time delays, effects of signal quantization and triggering conditions, stability, robustness, and performance, and make design decisions accordingly.