Multi-agent Systems
Mininet for VFN/SDN simulations
MASS general simulator
Netlogo programming and modeling environment, not very scalable, Lisp is used
NS-3 general network simulator, newest standards and protocols are usually not available, for 5G projects, see for example https://apps.nsnam.org/app/nr/
OMNeT++ general network simulator
Matlab + Simulink for low level modeling, not always efficient unless you use more advanced functions
Java for own efficient code
Akka: actor based simulator which could be more scalable than the ordinary simulators, for millions of actors per GB and tens of millions messages per second.
It can be used and done programming with Scalla, but there are alternatives starting from Erlang. Actor based simulators have an internal messaging mechanism suitable for multiagent system