The application I'm currently working on requires three ports to be opened. At the moment these are 5024 through 5026 but on reading around I discovered that these lie in the ICANN registered range (i.e. ports < 49151).
Is there any need for me to inform any organisation that I plan to use these ports if it's within a local network only or can I just go ahead and use them?
You can just go ahead and use them. The only way you'd need to notify ICANN is if you were going to have a significant number of clients using those ports in general use; in that case, you would want to try to register the application with the port to prevent potential collisions with other applications using those ports.
How big of a project is it? If there are more than a few thousand internet-exposed users, you may want to investigate informing them somehow. If its on a closed LAN of any size, it doesn't matter at all.
the language in the relevant RFC is that applications SHOULD NOT use unregistered ports. Nobody's going to sue you if you use them; the only issue you'll get is that if someone else decides to (1) use the same port (2) not register it, you'll confuse the heck out of each other. As McWafflestix says, you can go ahead and use them.
Related
Supposed I have two services that need to share and / or exchange data. Both instances are separate from each other, and they shall not know anything about where the other part is located.
Now in order for them to be able to share and / or exchange data, they need to connect to each other.
How do they find each other without the need to configure the IP addresses explicitly? In other words: How could they detect each other automatically?
Basically, I have two ideas:
Pull: You need to have a central service where they register. Then you can ask that service for the address of a service, and that service then returns those data. While this works, it has the drawback that it only shifts the problem to the next level: What if I have multiple instances of that service, and I don't want them to know each other in advance?
Push: Each service broadcasts its own address, so that other services get it to know. Each service repeats this from time to time. Drawback: This does hardly work in the internet.
Any idea of how I could solve this in an intelligent way?
PS: If you want to say so, I'm looking for a way to handle dynamic IPs without the need for a central DNS server.
The usual way is to have some fault-tolerant server where services register and can then look for other services - Curator framework implements that over zookeeper.
If you want autodiscovery then you should probably implement some sort of gossip protocol so that the servers would know which other servers are out there in a reliable way. You should keep in mind that getting gossip protocols right is tricky (e.g. some of past Amazon cloud failures where due to problems in their implementation)
"broadcast packets are not forwarded everywhere on a network, but only to devices within a broadcast domain."
If your devices are on different broadcast domains then broadcasting is not going to work.
You are probably going to have to implement your own central service, unless you can use one of the free dynamic dns servers, for example: Free
I have created a Business Management System which is to be used by retailers with or without multiple sites.
It is important that a logged in user identifies his/her location, or site, so that the system can perform site related tasks automatically.
I currently have a database of locations which includes an IP Prefix field, when the user goes to the log in page it looks for the first 5 digits of the current IP address, then:
If start of current IP matches a stored record it assumes user is at
that site.
If no IP matches then it asks the user which site they're in and asks them to update the IP.
This basic, and manual check works when the sites are a fair distance away or are on different ISPs for certain, the update is usually only required after a router restart and I've been using the system myself for about 4 years with no issues... BUT... I am not confident with it, so my question is; is there a better solution?
I realise the IP address is probably not the way as the best that gives me is the location of their ISP, but that's not what I need.
In case it matters I am using ASP.NET coding in VB
Also, should mention, I'm looking for desktop based application, not mobile.
I think you are going to have to rely on user input for this one. It's impossible (or at least, very very difficult) to know whether a user is using a proxy or not, and if they are you have no way of knowing where they really are. This is right and proper; would you trust every website you access with that kind of information? I sure as hell wouldn't.
You can't use the IP address to give you 100% reliable location data if your clients connect over the internet (they could be going through a proxy or as you said you might just get the ISP's IP address)
Your best bet is to use javascript to get the users geolocation: W3 Schools Example
More complex example on html5demos
No, of course it is not possible to reliably locate an user by IP Adress.
That adress can be faked, so the base of your info is not reliable.
I have a network of computers connected in form of a graph.
I want to ping from one computer(A) to another computer(B). A and B are connected to each other through many different ways, but I want to PING via only a particular edges only. I have the information of the edges to be followed during pinging available at both A and B.
How should I do this?
You could source route the ping but the return would choose its own path.
Furthermore, source-routed packets are often filtered due to security concerns. (Not always, they are useful and sometimes even required at edge routers.)
If the machines are under your local administrative control, then you could ensure that source-routed packets are permitted. As long as you are able to start a daemon on machine B, you could also easily enough design your own ping protocol that generates source-routed echo returns.
Well, this is actually done by routing protocols that are configured on the media in between the computers (routers I expect). I think there isn't a way where you can say "use that specific route". The routers have different protocols (OSPF, EIGRP, RIPv2) and they do the load balancing. The only way you would be sure of one specific route is to use static routing, but this isn't dynamically done where your computer decides the route.
This is normal because :
if you would be able to chose a route, DoS would be quite easy to do to kill one route.
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.
When developing an app that will listen on a TCP/IP port, how should one go about selecting a default port? Assume that this app will be installed on many computers, and that avoiding port conflicts is desired.
Go here and pick a port with the description Unassigned
First step: look at IANA listing :
There you will see at the tail of the list
"The Dynamic and/or Private Ports are those from 49152 through 65535"
so those would be your better bets, but once you pick one you could always google on it to see if there is a popular enough app that has already "claimed" it
If by widely-used, you mean you want to protect against other people using it in the future, you can apply to have it marked as reserved for your app by IANA here
The most comprehensive list of official IANA port numbers and non-official port numbers I know is nmap-services.
You probably want to avoid using any ports from this list (Wikipedia).
I would just pick one, and once the app is used by the masses, the port number will become recognized and included in such lists.
Choosing an unassigned one from the IANA list is usually sufficient, but if you are talking about a commercially-released product, you really should apply to the IANA to get one assigned to you. Note that the process of doing this is simple but slow; the last time I applied for one, it took a year.
As others mention, check IANA.
Then check your local systems /etc/services to see if there are some custom ports already in use.
And please, don't hardcode it. Make sure it's configurable, someway, somehow -- if for no other reason that you want to be able to have multiple developers using their own localized builds at the same time.
If this is for an application that you expect to be used widely, then register a number
here so no-one else uses it.
Otherwise, just pick an unused one randomly.
The problem with using one in the dynamic range is that it may not be available because it may be being used for a dynamic port number.
Well, you can reference some commonly used port numbers here and try not to use anyone else's.
If by "open to the public at large" you mean you're opening ports on your own systems, I'd have a chat with your system administrators about which ports they feel comfortable with doing that with.
Choose a number that is not very common
Choose a default port that doesn't interfere with the most common daemons and servers. Also make sure that the port number isn't listed as an attack vector for some virus -- some companies have strict policies where they block such ports no matter what. Last but not least, make sure the port number is configurable.
Use iana list. Download the csv file from :
https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.csv
and use this shell script for searching for unregistred ports:
for port in {N..M}; do if ! grep -q $port service-names-port-numbers.csv; then echo $port;fi; done;
and put 2 numbers instead of N and M.