An application server system is provided having a core engine connecting one or more protocol providers to one or more applications. In a preferred embodiment, the one or more applications run on a respective one or more virtual machines having their own execution threads. A thread pool may be used to spawn instances of applications or scripts. Preferably, the core engine, the protocol providers, and each of the one or more virtual machines run in separate AppDomains. In another embodiment, a visual designer is provided preferably having XML conversion capability and interactive debug capability.