mmorpg2d/Assets/Mirror/Examples/Tanks/Scripts/Projectile.cs

using UnityEngine;

namespace Mirror.Examples.Tanks
{
    public class Projectile : NetworkBehaviour
    {
        public float destroyAfter = 2;
        public Rigidbody rigidBody;
        public float force = 1000;

        public override void OnStartServer()
        {
            Invoke(nameof(DestroySelf), destroyAfter);
        }

        // set velocity for server and client. this way we don't have to sync the
        // position, because both the server and the client simulate it.
        void Start()
        {
            rigidBody.AddForce(transform.forward * force);
        }

        // destroy for everyone on the server
        [Server]
        void DestroySelf()
        {
            NetworkServer.Destroy(gameObject);
        }

        // ServerCallback because we don't want a warning
        // if OnTriggerEnter is called on the client
        [ServerCallback]
        void OnTriggerEnter(Collider co) => DestroySelf();
    }
}