I've been asked to implement VPN capabilities in an existing software project on an embedded system, in order to make the device available via network to an external server while avoiding trouble with firewalls (no need for encryption, just to make it accessible).
Unfortunately, the embedded system is based on a Cortex-M4 MCU, therefore Linux, which would allow for VPN nearly out of the box, is not an option. All I've got is an RTOS and a working LwIP stack.
I've used VPNs in the past. However, my network knowledge is rather limited concerning implementing VPNs, so I'm rather stumped. As I think, I'd use the current LwIP instance for building up the tunnel connection, and the application would use a second instance for the actual network communication, while the network interface of the second instance is a virtual one (like a tap device on linux), encapsulating its low level data and tranceiving it via the tunnel connection of the first LwIP instance.
Maybe this way I'd be able to create a custom solution for the problem, but the solution should conform to any standards (as the server will be any kind of sophisticated system).
So I wonder if anyone has been confronted with a task like this, and would appreciate any hint what to do, at least a direction where to look at.
Thanks in advance!
Related
I'm currently looking at options to allow me to build a remote COM-port solution.
The idea is to be able to access from my remote PC, another PC that's directly connected to a device locally via its serial COM-port.
I know that the obivous answer is to use a VPN between the 2 Internet connected PCs.
However, I need this solution to be as seamless to the end-user as possible.
i.e. no installing and configuring VPN software, etc.
So I was thinking that WebRTC would be great because the end-user can simply use their web-browser and not have to install any additional software.
My question is, is it possible to stream the COM port data between the 2 PCs via WebRTC?
If so, can you please point me in the right direction as to how I can go about achieving this?
Sorry if this is a ridiculous question, I'm very new to WebRTC, just exploring my options.
Thanks.
That should work great!
Networking wise you get NAT Traversal. That means the two computers can be in completely different networks, and still communicate. You may have to run a TURN server if P2P isn't possible.
Data wise you can exchange anything you want via data channels. It is datagram based and you can send/receive binary data. You get a callback telling you how much has been delivered, that way you can detect backpressure.
Are you ok with installing software on the remote host? You can do something like Pion WebRTC's data-channels. This shows you can have a browser connect to a Go process via WebRTC. Then use tarm/serial on the remote host to interact with the device.
If you want a browser on both ends there is the Web Serial API I haven't used it myself though. That locks you into only doing Chromium which might be an issue.
I would like to develop a little daemon software that will be run on a Windows computer.
I am trying to know if a 3D printer connected through the network (TCP/IP assigned through DHCP) is currently printing, or is it idle.
I believe the fact that it's a 3D Printer is of little interest here, and the same would apply to a regular inkjet/laser network printer.
I have some background in TCP/IP, Networking but very little knowledge about drivers and devices status querying.
Is there anyway to identify packets from a specific device inside the network?
Is this the way to go (listening to packets passing through the network), or is there an easier way?
Thanks a lot for your help.
Not sure if this will help, but OctoPrint (http://octoprint.org) gives you a web based interface for your 3d printer. Then you could pretty easily scrap the web page to see if it's busy or not, and you just need to be able to make an HTTP connection and parse HTML. That might be an easier path.
I'm currently building a network monitoring system that will notify me if any interface errors or network issues. after building it we would like to be able to test if it works before implementing it to our network, so need a way of simulating network interface errors on a switch or networking device?
I was thinking about cutting ethernet cables or terminating them wrong, but ideally I need soemthing that can create loads of different types of interface errors
any help would be much appreciated
Sean
You could download Nagios which is a powerful, enterprise-class host, service, application, and network monitoring program. Designed to be fast, flexible, and rock-solid stable. Nagios runs on *NIX hosts and can monitor Windows, Linux/Unix/BSD, Netware, and network devices.
you can download other network monitoring systems from sourceforge they have many different network tools written in different languages most of them are open source. you can take notes of their
design and maybe add to the application you building.
if you want to test your application the best thing to do is to tested on real environment, I believe their might be one or two Virtual Lab.
But Ideally I would tested on real interfaces
One of the ways to simulate network failures would be to dynamically change the firewall settings. You can make packets drop, hosts, disappear, etc. This doesn't require any physical damage to anything :)
I'm coding an extension for a customer, one of the requirements is that the extension also works offline because internet services are not that reliable, my customer's business can't stop but can deal with "stale" data, thats a nice tradeoff I guess.
Therefore, I want to code some kind of distributed cache as an extension to synchronize local data among the N nodes that will be connected running the same application and thus synchronize with the real database, hosted on the internet.
In order to achieve that I imagined that I would need to make a network broadcast and listen to incoming broadcasts, then every node that starts to run my application will broadcast it's IP address and become available as a new node for the distributed cache, failover is very important here.
I googled some possibilities I initially thought but none of them will work, I guess. The first was to do it just with HTTP, the second was to use Google Native Client to write C++ code that could run network code and thus do the broadcast, but it has limitations. Right now I'm thinking to use Java Applets but I don't really know if they have some limitations related to networking or if Chrome Extensions has any limitation with Java Applets.
Any ideas on how to do it? Using some of the stuff I suggested or another approach?
You could create an NPAPI extension, which would not be restricted by Chrome at all.
I have a somewhat basic understanding of network programming (and networking concepts in general) from taking a networking course in university a few years ago.
I remember being able to create a simple chat application, where the chat server is used as a central directory aware of which clients are currently online, but once a client knows another client it wants to chat with, the actual messages between them don't need to go through the server. I remember we could only test this over a bunch of LAN machines.
This C# chat program also has several comments mentioning that the program does not work over the internet: http://www.geekpedia.com/tutorial239_Csharp-Chat-Part-1---Building-the-Chat-Client.html
My question is why do these applications not work over the internet when "commercial" chat applications can. Surely, there is some way to make my computer accessible to the outer network even if its IP address is not valid outside the network of the ISP.
I see no problem with the linked-to code. The server doesn't even bind to a local address, which means it will listen for connections on all ip-addresses on the computer. There is however a comment for in the server article where the user changed the TcpListener object creation to bind to a specific address, which means clients only can connect to that specific address.
In the original server design, with using TcpListenet with only a port number, there should be nothing preventing its use on an Internet connected computer, unless there is a firewall blocking access.
Were you aware of networkComms.net and in particular the short chat example demonstrating the functionality here (It's less than 15 lines of code)? This was written specifically for people writing server-client apps in c# and given most of the problems you might come across will already have been solved and it might save you some time. This library is completely plug & play and has no issues working over the internet (as long as you can setup the necessary port forwarding where necessary).
Generally if both of your targets are behind NAT (so no true external ip addresses) and you are unable to configure port forwarding you need to look at 'TCP / UDP hole punching', quite an advanced technique.