?

Simulators like Omnet, NS2, Qualnet and NetSim can be used, but Contiki OS -Cooja  simulator is better than existing simulation tools.

 thank you ver much @Sukwinder

Simulators for IOT

1- Contiki OS + Cooja simulator

As we know, IoT will have various devices and can be divided into different networks. Thus, your security threat model needs to focus a certain level, but not all the levels including hardware, OS, network protocol, and application...The existing answers have clarify the good network simulators you can adopt (Cooja is a cross-level simulator but the others also can run with specific emulators like Qemu and etc).

see:http://www.contiki-os.org/start.html#start-cooja

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2-SimpleIoTSimulator

SimpleIoTSimulator The InternetOfThings Simulator SimpleIoTSimulator™ is an easy to

use, IoT Sensor/device simulator that quickly creates test environments made up of thousands of sensors and gateways, all on just one computer.

System Requirements

64-bit RedHat Enterprise Linux (6.x or higher)

for more details:

http://www.smplsft.com/SimpleIoTSimulator.html

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3- NetSim v9

NetSim v9 (Latest Released Version, Feb 2016)

see this :

Research on Internet of Things(IOT) using NetSim

https://www.youtube.com/watch?v=ManEw7jXkaw

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4- Internet of Things Simulator GUI Demo

to understand how its work :

https://www.youtube.com/watch?v=QuvEiooip4U

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5- AutoSIM IoT - Internet of Things Simulator

AutoSIM is the worlds first IoT simulator that can simulate 100+ million devices on a cluster of servers and supports 10 protocols below...

SmartM2M

LWM2M

CoAP

MQTT

Automatski (Streamer & Chatterbox)

Rest

Websockets

UDP

XMPP

AMQP

other custom protocols

see this :

https://www.youtube.com/watch?v=VlNIcmP8tvA

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Regards.. 

Thank you very much Ameer

thank for the info

https://security.cse.iitk.ac.in/sites/default/files/Master_Thesis.pdf

thanks Hamit, its really good