# Multi-Vehicle Simulation with JMAVSim
This topic explains how to simulate multiple UAV (multicopter) vehicles using JMAVSim and SITL. All vehicle instances are started at the same position in the simulation.
This is the easiest way to simulate multiple vehicles running PX4. It is suitable for testing multi-vehicle support in QGroundControl (or the MAVSDK (opens new window), etc.). Multi-Vehicle Simulation with Gazebo should be used for swarm simulations with many vehicles, or for testing features like computer vision that are only supported by Gazebo.
# How to Start Multiple Instances
To start multiple instances (on separate ports):
- Build PX4
- Run sitl_multiple_run.sh, specifying the number of instances to start (e.g. 2):
- Start the first instance:
- Start subsequent instances, specifying the simulation TCP port for the instance:The port should be set to
./Tools/jmavsim_run.sh -p 4561 -l
Ground stations such as QGroundControl listen for all vehicle instances on the PX4's remote UDP port:
14550 (all GCS traffic is sent to the same remote port).
Developer APIs such as MAVSDK or MAVROS listen on sequentially allocated PX4 remote UDP ports from
14540 (first instance) to
Additional instances all connect to port
# Additional Resources
- See Simulation for more information about the port configuration.