= roscore =
roscore is a collection of [[Nodes|nodes]] and programs that are pre-requisites of a ROS-based system. You '''must''' have a roscore running in order for ROS nodes to communicate. It is launched using the {{{roscore}}} command.

NOTE: If you use [[roslaunch]], it will automatically start `roscore` if it detects that it is not already running (unless the `--wait` argument is supplied).

`roscore` will start up:

 * a ROS [[Master]]

 * a ROS [[Parameter Server]]

 * a [[rosout]] logging node

There are currently no plans to add to `roscore`.

== Usage ==
The `roscore` can be launched using the `roscore` executable:

{{{
roscore
}}}
It will also automatically be launched part of any `roslaunch` process if `roslaunch` detects that it is not running.

You can also specify a port to run the master on:

{{{
roscore -p 1234
}}}
NOTE: if you use the port switch, you will probably have to pass in this switch to any separate `roslaunch` files you launch as well. In addition, do not forget to change the environment variable ROS_MASTER_URI before, e.g.

{{{
$export ROS_MASTER_URI=http://YourPC:1234/
$roscore -p 1234
}}}
== roscore.xml ==
The nodes launched as part of roscore are defined in `roslaunch/roscore.xml`. It is generally not recommended that new nodes be added to this file as it affects every `roslaunch`. These changes are also less portable to other people using ROS.

`roslaunch` treats nodes listed in `roscore.xml` differently: it searches for nodes running with the same name and will only launch ones that aren't already running.

== roscore Map ==
{{http://cfile239.uf.daum.net/original/27280B4758382EBD3713E6||height="303",width="700"}}

== roscore class map ==
{{http://cfile212.uf.daum.net/original/245D753758381E7523D4D5||height="323",width="700"}}