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What's the purpose of sbt-rc-probe-0-13 and sbt-rc-ui-interface-0-13 in Activator?
When starting Typesafe Activator using activator ui, there are messages starting with Getting. What do sbt-rc-probe-0-13 and sbt-rc-ui-interface-0-13 do for activator?
➜  no-trace-deps  activator ui
Checking for a newer version of Activator (current version 1.2.10)...
   ... our current version 1.2.10 looks like the latest.
Found previous process id: 36033
FOUND REPO = activator-local @ file:/usr/local/Cellar/typesafe-activator/1.2.10/libexec/repository
Play server process ID is 39625
[info] play - Application started (Prod)
[info] play - Listening for HTTP on /127.0.0.1:8888
[info] a.e.s.Slf4jLogger - Slf4jLogger started
Getting com.typesafe.sbtrc sbt-rc-probe-0-13 1.0-c50ddab5e1332398049a2a649261e1ca24577479 ...
downloading file:/usr/local/Cellar/typesafe-activator/1.2.10/libexec/repository/com.typesafe.sbtrc/sbt-rc-probe-0-13/1.0-c50ddab5e1332398049a2a649261e1ca24577479/jars/sbt-rc-probe-0-13.jar ...
    [SUCCESSFUL ] com.typesafe.sbtrc#sbt-rc-probe-0-13;1.0-c50ddab5e1332398049a2a649261e1ca24577479!sbt-rc-probe-0-13.jar (12ms)
:: retrieving :: org.scala-sbt#boot-app
    confs: [default]
    2 artifacts copied, 0 already retrieved (414kB/8ms)
Getting com.typesafe.sbtrc sbt-rc-ui-interface-0-13 1.0-c50ddab5e1332398049a2a649261e1ca24577479 ...
downloading file:/usr/local/Cellar/typesafe-activator/1.2.10/libexec/repository/com.typesafe.sbtrc/sbt-rc-ui-interface-0-13/1.0-c50ddab5e1332398049a2a649261e1ca24577479/jars/sbt-rc-ui-interface-0-13.jar ...
    [SUCCESSFUL ] com.typesafe.sbtrc#sbt-rc-ui-interface-0-13;1.0-c50ddab5e1332398049a2a649261e1ca24577479!sbt-rc-ui-interface-0-13.jar (4ms)
:: retrieving :: org.scala-sbt#boot-app
    confs: [default]
    1 artifacts copied, 0 already retrieved (32kB/4ms)
[info] application - error getting name from sbt: sbt process never got in touch, so unable to handle request NameRequest(true)
[info] application - using file basename as app name: no-trace-deps
[INFO] [09/26/2014 19:41:14.587] [default-akka.actor.default-dispatcher-3] [akka://default/user/app-no-trace-deps-1/socket] Firing up web socket


These were part of the old sbt-remote-control API (the prototype for sbt server).
The "probe" is what sits inside sbt and communicates task results/commands to/from the activator process and the sbt server.
The 'ui-interface' is an API where plugins can directly send messages to activator from within sbt.
These will make a bit more sense with the new sbt-server pre-release where "ui-interface" is renamed "server-interface" (I think) and the Play plugin can directly communicate to clients (like IDEs/Activator).
