TSpaces acts as a reminder service, carries out any tasks that you assign to it, reports incoming messages and delivers outgoing messages, and notifies you of any events in which you're interested. By adding additional client applications, TSpaces can be used as a universal print service, email service, pager service, remote control service, and so on. Communication is anonymous. The sender needn't know about the receiver, and vice-versa. Sender and receiver only need to know about tuple space, which mediates all communication.
Communication is asynchronous.
Since it is written in Java, TSpace client applications can be loaded dynamically into any network-attached computer. The TSpaces package comes with several useful applications that show how to build TSpace clients.