The Activator is a background process, or daemon, that must be running on a system that can receive incoming requests from other Distributed systems. The activator is a stand-alone executable program, separate from the Smalltalk image. The activator has two main purposes:

As an alternative to the Activator program, SST server object spaces allow for connections directly from client object spaces. This feature simplifies the setup required on the server and speeds up the connection time. Without a front-end program like the Activator, SST does not support automatic start up of the server object space, triggered by a client request. Also, to run multiple object spaces on the same server machine, SST requires that each server object space be defined with a different URL. For applications using the TCP/IP transport, this would mean that each server object space would require a different port number and the clients would need to know the port number of the server object space they desire.