Although current electronic commerce (e-commerce) technology plays an important role in today's economy, it is still not full-fledged for the lack of enough security and flexibility. We propose eTNet, a smart card network architecture for electronic transactions, which fills up the gap and further extends our previous work, the eTRON architecture. The eTNet framework is made up of an overlay network of smart cards over the Internet, which enables electronic transactions to be executed securely over the Internet, without relying on any central authorized servers. Based on the models of the eTRON architecture, we have designed and implemented eTNet and its components, including protocol stack, servers, and client software. In order to evaluate our system, an electronic ticket system was implemented on this framework as a case study, through which we proved that eTNet successfully adds security, flexibility, and interoperability in electronic commerce services.