I'm creating a WiFi program for Windows, I'm new to network programming.
I'm using the Native Wifi API to get information about a network but now I want information about the other devices that are connected to a network.
Does anybody know what I should learn to accomplish this? Do I need to use winsock?
You can do this via UPnP (assuming your AP supports UPnP, but most do).
You'd connect to the WLANConfiguration service of your UPnP access point, and read the TotalAssociations to get the number of associated devices, and the AssociatedDeviceMACAddress and/or AssociatedDeviceIPAddress variables to get the addresses of the associated devices. The latter might give you IPv4 or IPv6 addresses, or it might give you host names.
The TotalAssociations variable is "evented", which means you can have the access point tell you want the number of associated devices changes, and re-enumerate their addresses when that happens.
Microsoft also provides a UPnP API that may be helpful (though I've never used it personally, so I can't say much more about it).
References
UPnP Architecture specification
WLAN Configuration Service specification
Related
I am making a program where I have to use TCP/IP connection to transmit and receive data between devices. I would like to be able to detect the names and IP addresses of all devices that are using the network(The device running the program is also on the network). I am using C++ on windows, I looked through the Windows Native Wifi API but couldn't find anything. Is there an efficient way to get the names and IP addresses of all devices connected to the network?
There are a few competing techniques, such as Apple Bonjour. That's pretty much a clue that there is no single way that gives you all names of all devices - this is not standard IP-level functionality.
I want to create a C++ application that can be used (in part) to communicate between users on a local area network using UDP. Each instance of the application will have a thread dedicated to listening for other instances of the application and broadcasting its presence to other instances.
Is there a reliable way to perform this type of broadcast/listening on the LAN using pure C++ and POSIX system calls? I know there's no generally reliable way to find all IPs on a LAN, but I assume this is only because other devices are not willing to respond to pings.
Don't re-invent the wheel. There are two existing technologies, that, when combined, solve your problem in a standardized, well-designed, proven manner:
RFC6762 mDNS (Multicast DNS) is a protocol that works almost exactly like DNS, except it works using IP multicast. Instead of sending your DNS request to a unicast address, you send your DNS request to a multicast group, and any member of that group can answer your request (so you may get multiple answers).
RFC6763 DNS-SD (DNS-based Service Discovery) is a way to encode Services as DNS entries, which allows you then to retrieve Services from DNS using specially encoded hostnames. (For example, looking up the hostname _ipp._tcp.example.com would return a list of all printers that support the Internet Printing Protocol over TCP within the domain example.com)
So, we have one protocol that allows us to ask DNS about Services, and we have one protocol that allows us to ask a group of hosts to answer DNS queries … when we put the two together, we get a way of asking hosts for services! The combination of those two protocols is sometimes called Zeroconf networking, and is already implemented in macOS, iOS, tvOS, and watchOS (where it is called Bonjour), Android, most Unices (via Avahi, a portable implementation of those two protocols), and many home devices such as TVs. E.g. Spotify Connect, ChromeCast, Philips Hue and many others are also based on it. It's how iTunes devices find each other on the local network, for example.
Unfortunately, support in Windows is still limited, at the moment it seems to only exist for Windows 10 apps implemented in ECMAScript. (However, nothing stops you from shipping your own implementation with your app, and AFAIK, both Avahi and Apple's mDNSResponder work on Windows.)
So, what you would basically do is to send an mDNS query to the mDNS multicast group and ask for _myprotocol._udp.local. Then, assuming that your application registers itself with the OS's mDNS service (i.e. Bonjour on macOS, Avahi on Unices, …), you would get back a list of all hosts on the local network that support your protocol.
I need to write a win32 c/c++ application which will be able to determine whether the PC it's running on is connected to one of 2 networks. The first network is the company LAN (which has no internet connection) and the second network is a standalone switch with a single PC connected to it (the PC that the program is running on).
I'm pretty new to network programming but so far I have tried testing to see if a network drive which is held on our LAN can be mapped. This works fine if the PC is connected to the LAN, the drive mapping succeeds so so LAN detection is successful. However, if the PC is connected to the switch, this results in a VERY long timeout which is not a suitable as it will delay the program so much as to make it unusable.
Does anyone have any alternative suggestions?
I'm using c/c++ in VS 6.0
[Update]
Whilst trying a few different ideas and looking at some of the suggestions below I thought I should update with some additional information as many (if not all) of the suggestions I don't think will work.
(1) The aforementioned LAN has no external connections at all, it is completely isolated so no resolving of external DNS or pinging websites is possible.
(2) Hostname, MAC address, IP, Default Gateway, Subnet etc etc (basically everything you see in ipconfig -all) are all manually configured (not dynamic from the router) so checking any of these settings will return the same whether connected to the LAN or the switch.
(3) Due to point (2), any attempts to communicate with the switch seem to be unsuccessful, in fact almost all networking commands (ping, arp etc) seem to fail - I think due to the machine trying to connect to the LAN when it isn't there :-(
One thing I have found which works is pinging the default gateway IP which times out when connected to the switch. This is sort of ok as I can reduce the timeout of ping so it doesn't just hang for ages but it feels like a bit of a hack and I would certainly appreciate any better solutions.
Thanks
As far as TCP/IP is concerned there is no such thing as a LAN on WAN. There are a set of non-internet routable addresses like 192.168.x.x and 10.x.x.x but these are sometimes used by ISP short of IP addresses.
You best bet is to use Asynchronous APIs when making TCP/IP connections. WIN32 defines a whole buch of OVERLAPPED APIs for this purpose. This will prevent your application from grinding to a halt while waiting for a remote connection.
Alternatively put the socket stuff into another thread and then only notify the UI when the operation is done.
I would first try to differentiate between the two using information available locally--that is, from your computer. Does the output of ipconfig /all differ depending on which network you're connected to? If so, exploit that difference if you can.
Is it possible to get the MAC address of the standalone switch? Of the switch that controls the company LAN? That would be a sure way to tell. Unless somebody cloned the MAC address.
If you try using the existence or non-existence of some network service to determine which network you're connected to, you can never be sure. For example, if you failed to map that network drive, all you know is that the network drive isn't available. You can't say for certain that you're not connected to the company LAN. Same is true if you use ping. Lack of response from a particular machine means only that the machine didn't respond.
Various things you can look at for differentiation:
DNS domain name (GetComputerNameEx)
MAC address of gateway (ping it, then GetIpNetTable)
Routing table(do you have a gateway and default route on the company LAN)
WNet discovered network resources (WNetOpenEnum, WNetEnumResource)
Ability to resolve external hostnames (try a 5-10 names like www.google.com, www.microsoft.com and so on, if one resolves you should have internet)
You'll have to decide how many indicators are "enough" to decide you're on one or the other LAN though if tests fail. Then keep retrying until you have a definite result.
http://msdn.microsoft.com/en-us/library/aa366071%28v=VS.85%29.aspx has a lot of network related functions that you can experiment with to create further indicators.
Problem: Mediate USB traffic/data
I would like to accept inbound traffic on a specific USB port and replicate it exactly as outbound traffic on another specific USB port, in effect accomplishing a USB proxy. By extension, then, the connections need to be two-way. An additional requirement is that the port must be able to fake its identity (vendor ID, product ID, ...) as seen by an external device. Should the given solution also be able to dump/log the raw traffic, that would be fantastic, although not a requirement. Target platforms are Windows and/or Linux (any will do).
Before going on an epic journey and writing a custom driver, which is fairly likely to induce brain damage, I would like to ask if anyone has ever done anything similar, or could possibly conceive of the pieces needed to assemble this puzzle. :)
I don't think this is doable out of the box, without extra hardware.
What kind of device can you expect to connect to the "upstream" port of the proxy? Assuming there's a regular device (let's say a mouse, just as an example) on the "downstream" port, the device at upstream needs to be a USB host in order to handle the USB device in a meaningful way.
But you can't connect the USB port of your computer (which already is the host for all its USB root ports) directly to another computer, that's a total violation of USB's network topology. Both ports contain +5 V power rails, and if you connect those together, you're likely in for a shock. And/or a private fireworks display. Or a trip to your nearest motherboard and/or PSU retailer ...
Also, since USB is quite dynamic and so on, I don't think you can expect the bitstream from one port to be meaningful if repeated out another port, since address information etc might change.
There are 100% software USB analyzers, like http://www.usblyzer.com/, but I'm not so sure about proxies like what you describe.
At my work we have used this Beagle USB Analyzer. It sits between device and host and captures all traffic without interruption. It works in windows and linux and functions even with USB 2.0 highspeed ports.
http://www.totalphase.com/products/beagle_usb480/
Highly recommended.
i have known that winpcap library enabled a person to obtain advanced information about installed devices...
given all the networking devices found in the computer, how will i know which one of this has an internet connection?!
thanks:)
You typically don't care about this. Normally you just ask the network stack to make a connection, and don't worry about details.
However, each "device" will have its own IP address. You can request the network stack to use this IP address when making a connection.
Now, to figure which devices have an intenet connection, iterate over all of them, obtain their IP address, and try to create a connection from that originating IP to a destination IP on the Internet. Typically you already know such a destination IP, e.g. your companies webserver.
GetAdaptersInfo() will give you a list of all network adapters installed in a form that you can then use in GetIfEntry(). This latter function will tell you the operational status of an adapter, so you can at least tell if the adapter is plugged into a live hub/switch/router.
If you are particularly interested in IP connectivity, you could look to see if a default gateway is configured for that interface. Don't forget you might have to support IPv6 as well as IP4 if you try this.
Correlating the network adapters found by GetAdaptersInfo() with those found by pcap_findalldevs() is left as an exercise for the reader. I don't remember the details but it was fairly obvious.