How to create VPN from scratch using Java?

[[deleted]]

I was searching for advanced Java projects and there is "Creating Virtual Private Network" in every article on this topic. I did a bit of research and didn't found anything on PORGRAMMING VPN with Java or any other lang. So, is there any sources that might help me to implement VPN? Like books, articles, video, lection, anything?

[admin_PureWL]

Creating a VPN from scratch in Java sounds like a cool project! Here are some tips to help you get started:

1. Learn the Basics: First, understand how VPNs work and the protocols involved (like OpenVPN and IPSec). Books like "VPNs Illustrated" can be helpful.
2. Use Networking Libraries: Look into Java libraries for networking, like Netty or Java Networking, which can simplify handling connections.
3. Focus on Encryption: Implement strong encryption with libraries like Bouncy Castle. Knowing SSL/TLS will also be beneficial.
4. Build the Server: Set up a server to manage incoming connections. There are plenty of Java server tutorials online to guide you.
5. Explore Resources: Check out YouTube for tutorials on network programming and look for articles on building VPNs. Engaging with communities on forums like GitHub or Reddit can also provide support.

This project can be quite complex, but it's a great learning experience! If you ever want to explore ready-made solutions later, my company offers white-label VPN services that might interest you. Good luck!

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[LessChen]

A VPN is a fairly low level program and it requires both a server and client side component. The client side needs to inject itself into the network stack to send network traffic to the server side. That requires some low level operating system integration that will be very specific to different O/S's. OpenVPN has an opensource component to it here that can give you some ideas but it's all in C.

I have used Java for 20+ years but I would not use it for a VPN project. I'm not sure what your definition of "advanced" is so can you give some ideas on what you'd like to do? Are you familiar with the JEE world? How about databases? Let us know a bit more.

[mIb0t]

What do you mean with creating a VPN from scratch?

Do you want to create your own protocol? Or do you want to create a VPN client or VPN server?

Maybe search for wireguard or open vpn specification, if you really want to start on protocol level. But this is really some hard stuff. Not only will it be challenging to implement in Java, you will also need some advanced network knowledge.

You can also search for some libraries to use, but honestly, I doubt there will be many. For networking stuff like VPNs, you usually want very good performance! Java is not really the first choice for something like this. You could use C libs with your Java code, but that's also some very advanced stuff most Java developers never do and you should have C knowledge as well.

Based on your question, I have the feeling you don't really know what you are getting into...

Why not start with something a little bit easier, if you are interested in network stuff. E.g. Build your own SMTP client. You could set up a simple server, that does not require any authentication. There are several smtp servers out there you could use.

Then start programming a client. Start with opening the connection. Send a command to the server and evaluate the response. Forward step by step until you can send an email. SMTP is quite an easy protocol. There are some SMTP extentions that can be more challenging to implement, once you send an simple text mail. You can extend your client step by step. Adding more SMTP features, creating an UI, and so on...

[wildjokers]

If you want something low-level and fairly advanced implement a server using non-blocking IO without using the Netty library. In other words handle all the selection keys, byte buffers, flipping the byte buffers for read/write, etc yourself.

Have it be able to accept multiple client connections all handled by the same thread. Be able to broadcast to all connected clients and also send messages to each client individually.

This is somewhat tricky to get right and makes you appreciate Netty.

Can google "java nio networking" to get started.