which one to choose between p2p or client-server network architecture for advanced file sharing option with less resources and manpower. will u illustrate with strong opinion??
I would like to know more if anyone can intrude between and get access between the two users in P2P??
For long run and big scale I will obviously pick client-server mode.
It's indeed need more resources at the beginning than the P2P, but it's way more manageable (both in software and hardware) and make my life easier to maintain the performance.
Client server mode is only useful if you are planning to do the file sharing within LAN, otherwise you need to have a public IP. The PC with public IP acts as a server. If you have a p2p file sharing system then you probably need only one server with public IP for the rendezvous and hole punching process. so many PC can connect with each other and share. What do you mean by advance file sharing ?
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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!
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 :)
We published the game on russian server and 1% of people couldn't connect to server on 46xx port through raw TCP while they can load it's HTML page (through HTTP). Most of such people live in Germany, Israel....
Why is it so? What's the politics decisions lay behind it? We discovered that their such ports (which are free on IANA) are closed. Does it mean that such people cannot run Steam (and, then, play all games which you can buy through it), play WoW and many other modern games which use TCP through 4xxx ports?
Thank you.
ISPs have been known to filter certain ports for various reasons. Users should complain loudly to them (or switch) in order to send a signal that such is not to be tolerated. You can encourage them to do so but of course that doesn't solve your problem (or really answer your question).
Common reasons are:
- trying to block bittorrent traffic
- limit bandwidth usage (largely related to previous reason)
- security (mistaken)
- control (companies often don't want employees goofing off)
The easiest thing for you to do is run your game over port 443 (perhaps as an alternate). That's HTTPS and so will not generally be blocked. However, because HTTPS is encrypted, there's no way to inspect the stream to know if its web traffic or something else and thus you can run any data stream (encrypted or not) that you wish over it.
That's precisely correct. In fact every public web site would by default block all ports except the ones they expect to be running some traffic they would want to.
This is the reason many applications often try to encapsulate their programs to use port 80 which can't be blocked as long as some one wants http traffic to run.
They simply don't want any application that they haven't approved to run through their servers. If you have a sensitive server in public you surely won't want any one to use your machine for any apps that you don't allow. A common reason is applications that eat up bandwidth such as bittorent, edonkey, gnutella as well as streaming, voip and other high bandwidth consuming apps
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.
I'm making a network game (1v1) where in-game its p2p - no need for a game server.
However, for players to be able to "find each other", without the need to coordinate in another medium and enter IP addresses (similar to the modem days of network games), I need to have a coordination/matching server.
I can't use regular web hosting because:
The clients will communicate in UDP.
Therefore I'll need to do UDP Hole Punching to be able to go through the NAT
That would require the server to talk in UDP and know the client's IP and port
afaik with regular web hosting (php/etc) I can only get the client's IP address and can only communicate in TCP (HTTP).
Options I am currently considering:
Use a hosting solution where my program can accept UDP connection. (any recommendations?)
UDPonNAT seems to do this but uses GTalk and requires each client to have a GTalk account for this (which probably makes it an unsuitable solution)
Any ideas? Thanks :)
First, let me say that this is well out of my realm of expertise, but I found myself very interested, so I've been doing some searching and reading.
It seems that the most commonly prescribed solution for UDP NAT traversal is to use a STUN server. I did some quick searches to see if there are any companies that will just straight-up provide you with a STUN hosting solution, but if there even were any, they were buried in piles of ads for simple web hosting.
Fortunately, it seems there are several STUN servers that are already up and running and free for public use. There is a list of public STUN servers at voip-info.org.
In addition, there is plenty more information to be had if you explore SO questions tagged "nat".
I don't see any other choice than to have a dedicated server running your code. The other solutions you propose are, shall we say, less than optimal.
If you start small, virtual hosting will be fine. Costs are pretty minimal.
Rather than a full-blown dedicated server, you could just get a cheap shared hosting service and have the application interface with a PHP page, which in turn interfaces with a MySQL database backend.
For example, Lunarpages has a $3/month starter package that includes 5gb of space and 50gb of bandwidth. For something this simple, that's all you should need.
Then you just have your application poll the web page for the list of games, and submit a POST request in order to add their own game to the list.
Of course, this method requires learning PHP and MySQL if you don't already know them. And if you do it right, you can have the PHP page enter a sort of infinite loop to keep the connection open and just feed updates to the client, rather than polling the page every few seconds and wasting a lot of bandwidth. That's way outside the scope of this answer though.
Oh, and if you're looking for something absolutely free, search for a free PHP host. Those exist too! Even with an ad-supported host, your app could just grab the page and ignore the ads when you parse the list of games. I know that T35 used to be one of my favorites because their free plan doesn't track space or bandwidth (it limits the per-file size, to eliminate their service being used as a media share, but it shouldn't be a problem for PHP files). But of course, I think in the long run you'll be better off going with a paid host.
Edit: T35 also says "Free hosting allows 1 domain to be hosted, while paid offers unlimited domain hosting." So you can even just pay for a domain name and link it to them! I think in the short term, that's your best (cheapest) bet. Of course, this is all assuming you either know or are willing to learn PHP in order to make this happen. :)
There's nothing that every net connection will support. STUN is probably good, UPnP can work for this.
However, it's rumored that most firewalls can be enticed to pass almost anything through UDP port 53 (DNS). You might have to argue with the OS about your access to that port though.
Also, check out SIP, it's another protocol designed for this sort of thing. With the popularity of VOIP, there may be decent built-in support for this in more firewalls.
If you're really committed to UDP, you might also consider tunneling it over HTTP.
how about you break the problem into two parts - make a game matcher client (that is distinct from the game), which can communicate via http to your cheap/shared webhost. All gamers who wants to use the game matching function use this. THe game matcher client then launches the actual game with the correct parameters (IP, etc etc) after obtaining the info from your server.
The game will then use the standard way to UDP punch thru NAT, etc etc, as per your network code. The game dont actually need to know anything about the matcher client or matcher server - in the true sense of p2p (like torrents, once you can obtain your peer's IPs, you can even disconnect from the tracker).
That way, your problems become smaller.
An intermediate solution between hosting your own dedicated server and a strictly P2P networking environment is the gnutella model. In that model, there are superpeers that act like local servers, having known IP addresses and being connected to (and thus having knowledge of) more clients than a typical peer. This still requires you to run at least one superpeer yourself, but it gives you the option to let other people run their own superpeers.