For example, if only 4 nodes have to be launched (assuming there are only 4 drones in the simulation) in the same machine, the following change has to be made in line 5 of dorca.launch file in launch directory.
<arg name="nr" default="3"/>
and make sure the line 11 of of dorca.launch looks as follows
<include file="$(find dorca)/launch/dorca.launch" if="$(eval arg('nr') - 1 >= 0)">
Note : Make sure the total agents in the config file is same as the total nodes launched in the launch file.
Incase two machines are used in the network with each intended to control 2 drones, then the roslaunch file should be modified to launch 2 nodes (drones) in each machines with appropriate agent numbers for node.