The aspects like complete internet routing can be involved in the difficulties of a whole-featured VPN generally, while this network project outline aims to a basic application which contains a VPN client and a VPN server for easiness without exploring these challenges:

Project Outline

The objective is to develop a basic VPN system in which:

• The VPN server pays attention to get links from the VPN client.
• Once the VPN client is linked with the server, the entire client network traffic is routed by this safe link to a particular address.
• Traffic among the server and client is encrypted securely.

Essential Components

• VPN Server: It waits for links from clients initially. It creates a safe channel and sends traffic among the internet and the VPN client, after getting a connection from the client.
• VPN Client: Before forwarding the data above the network, it links to the VPN server and encrypts the data. The incoming data can also be decrypted through the VPN client.
• Encryption/Decryption Mechanism: To encrypt and decrypt the traffic which runs into the VPN, you can employ the in-built libraries of Java like javax.crypto.

Procedural Steps

Step 1: Set Up the Project

• In your familiar IDE, design a novel Java project.
• Two major classes such as VPNServer.java and VPNClient.java should be described well.

Step 2: Implement the VPN Server

• For incoming client links, establish a ServerSocket which listens on a certain port in VPNServer.java.
• Utilize a single thread to manage the interaction after approving the connectivity.
• To the data that is arrived from and sent to the client, incorporate encryption and decryption.
  

Step 3: Implement the VPN Client

• Develop a socket which links to the port and IP address of the server in VPNClient.java.
• Using this socket, route traffic to the server.
• For outgoing data, apply encryption and for incoming data, use decryption processes.

Step 4: Encryption and Decryption

• For encrypting and decrypting data, employ the Cipher class of Java. Particularly for this project, AES will be the best option.
• Keys will be swapped safely through a protocol such as Diffie-Hellman in a real-time situation. Assure that the client as well as the server implements the similar key for both the encryption and decryption processes.

Step 5: Testing

• Execute the VPNServer and after that run the VPNClient.
• It is necessary to make an attempt of transferring data from the client to the server; it can be any data stream or a basic HTTP demand.
• When the data is departing from the client, confirm it is encrypted and it should be decrypted only after reaching the server.

Example Code Snippets

       For learning motives, the following are the most shortened program snippets:

// Example VPN Server socket setup

ServerSocket serverSocket = new ServerSocket(portNumber);

Socket clientSocket = serverSocket.accept(); // Accept client connection

// Data input and output streams can then be encrypted/decrypted using Cipher

// Example VPN Client socket setup

Socket socket = new Socket(serverAddress, portNumber);

// Use the socket’s input and output streams for sending/receiving data

Considerations

• Protection: Discover TLS for high-safe applications. Throughout powerful encryption and secure key exchange specifically, this project reduces a lot of features in an actual VPN.
• Performance: The efficiency can be influenced by the encryption and decryption. For managing large data volumes, enhancement and profiling can become essential.
• Scalability: Determine in what way various concurrent links are controlled by your VPN server.

Is there any free simulator software for sensor networks?

       Simulators are essential to conduct the simulation process and more valuable. There are different kinds of simulators accessible and we can choose them based on the need of the project. We offer a list of few of the simulator software which are open-source and you can access at free-of-cost especially for sensor networks:

1. OMNeT++

• Outline: OMNeT++ is majorly for constructing network simulators. It is a component-oriented, modular and extensible C++ simulation library and model. For educational and exploration objectives, this can be implemented in a wide range.
• Features: It is more expandable using modules such as INET that contains the assistance for wireless and mobile simulations. This also provides a graphical runtime platform and robust IDE.
• Website: OMNeT++ official website

2. NS-2 / NS-3

• Outline: For investigation in networking that consists of sensor networks, Network Simulator 2 (NS-2) and its extension NS-3 are the highly utilized license-free network simulators in a broad range. Specifically for advanced network technologies, NS-3 has effective assistance.
• Features: This helps for a thorough designing of wireless interaction along with enlarged documents, sensor networks and a vast amount of network protocols.
• Website: NS-3 official website

3. Castalia

• Outline: Castalia depends on the OMNeT++ simulation model. This is a simulator which is typically for networks of low-power integrated devices, Wireless Sensor Networks (WSN) and Body Area Networks (BAN).
• Features: It is valuable for both the developers and investigators who intend to experiment with their WSN applications and protocols. It also provides practical radio channel and node frameworks and energy consumption designing.
• Website: Castalia can be identified on GitHub and is beneficial for particular legitimate project works, but not preserved in a proactive manner.

4. Cooja

• Outline: Cooja is developed for WSNs and Internet of Things (IoT) devices. It is a simulator inside the Contiki operating system.
• Features: It enables real firmware running with the help of emulation, assists simulating at the network-level as well as the mote-level and permits simulating networks of Contiki nodes.
• Website: Contiki-NG is the future generation of Contiki which is accessible at Contiki-NG GitHub and contains Cooja in it.

5. CupCarbon

• Outline: CupCarbon focuses on developing, visualizing and assessing IoT networks and digital city. It is specially a simulator of Smart City and Internet of Things Wireless Sensor Network (SCI-WSN).
• Features: Visual result of simulation situations, practical simulation of sensor deployment in city ecosystems and scripting for sensor action.
• Website: CupCarbon official website

6. TOSSIM

• Outline: Particularly for TinyOS WSNs, TOSSIM is an effective simulator. TinyOS is created for sensor network nodes and is considered as an event-driven operating system.
• Features: It has the ability of offering full control beyond the network platform and simulating thousands of nodes at the bit level by designing the network.
• Website: Get more information about TOSSIM and TinyOS from the TinyOS official website.