I would like to connect the nodemcu to some LEDs, running a HTTP server (RESTful presumably) and turn on/off accordingly. However, how can the devices in the same network find the device? I guess I could try static IP for esp8266, but that is not guarantee to work every time everywhere. So how can I scan the network to find that, or is there any better solution?
I think most people use multicast DNS (mdns) for this, a quick Google should give you some examples for the environment you use :)
I like using MQTT, which is a different protocol that uses a central broker, but it's probably not quite what you want.
Also, why would a fixed IP not work? Most routers allow to assign one based on MAC address, which should work consistently.
And finally, you should be able to set a hostname for the ESP (wifi_station_set_hostname in the ESP SDK, which I think you can call from Arduino also), which should make it known with your router under that name.
I set my DHCP server to always give the same IP address to my NodeMCUs based on their MAC addresses. They are also configured with mDNS but I don't have mDNS on my Android phone so it didn't help me.
Related
I want to send data(I think I can achieve it sending http requests) between two ESP's that are connected to the same LAN. I don't want to use one as an access point! I have one esp that is acting as a homekit device, and I want to send data(for example, sensor readings) to it from another esp. I've seen many tutorials where one device is acting as an access point, but that's not what I need. I also don't really need to access the esp data directly from my laptop, so I believe I don't need the html page. I would appreciate any help, code, or any existing tutorials, because I didn't find a single one.
Configuring one ESP as an AP is only done for convenience. You can configure both of them in STA (station) mode and they will connect to, e.g. your phone hotspot or your wifi router.
Connected to the same hotspot, they are on the same network, and they will be able to communicate with each other (unless the hotspot is configured to not allow this ... ). The tricky part will most likely be for the "client" to determine the IP address of the "server" in order to create the connection.
If you have admin access to the hotspot, you can cheat and hard code the IP addresses (assuming that the hotspot will assign the same IP address to the device the next time it sees it.)
It's also not difficult to use mdns (aka bonjour), which allows a network device to assign itself a local hostname. So you can name one ESP ("myserver") which allows the ESP running the client code to connect to "http://myserver.local"
This is somewhat of a general question, is it realistic to assume that a router can resolve any mobile device's MAC address without being already connected via wifi or bluetooth?
If the device is broadcasting, or if it's connected to another access point, then capturing the wifi data would allow you to capture the device's MAC address. Routers aren't generally set up to listen in that way, and I don't think it would be simple to configure that kind of behavior.
In general, if a device isn't connected to a wireless router/access point, you aren't going to be able to capture its MAC.
I would like to write a software running in a networked device, i.e. PC. It can automatically detect the other network devices' types. For example, it can detect there is a PS3, a Wii, an IPad running in the same network. Any ideas? Thanks,
You have two problems: first, detecting that a device is connected to your network and at 192.168.1.x. Second, somehow detecting what that device is.
The first is easy-ish to accomplish: there's discovery protocols like UPnP and Bonjour. However, in a home networking scenario, the easiest and most reliable way to get a list of connected devices is probably to pull the DHCP reservations from your router. You might have to scrape data from the router's HTML-based management interface—hacky as that may be—but it would work. (If you're using .NET, consider the HTML Agility Pack to accomplish this.)
Once you have a list of IP addresses of connected devices, your next problem is to figure out what each device actually is. This will be more challenging. Some possibilities:
You may be able to use the MAC address to help detect the device's vendor. (Here's a list.)
If you're using UPnP, you can ask the device what it is.
Use IP fingerprinting to determine what the device is.
Couple thoughts. The broadcast IP address - 255.255.255.255 is where devices talk and say "here I am". Should be able to listen to this and find ip addresses and more. Second, if devices are assigned an IP address by a DHCP client (obviously) you can usually find a list on the dhcp device. Devices often have names, this is a higher level protocol, like windows SMB, that you may have to interface with in order to get that information.
I'm working on a Wake on LAN service that will run from a web site and should interact with many different platforms - therefore, no Windows-only solutions. When a user registers their system with the web site, I need to get the MAC address to use in constructing the "magic" packet. I have a Java Applet that is able to do this for me and am aware of an ActiveX control that will work, but I'm wondering if there is a way to do this server-side by querying routers/switches. Since the system may be on any of a number of different physical subnets, using ARP won't work -- unless there's a way to configure the router(s) to perform the ARP on my behalf.
Anyone know of any network APIs, proprietary or otherwise, that can be used to look up MAC addresses given an IP address? I think we're using Cisco routers, but it's a complicated network and there may be multiple vendors involved at various levels. I'd like to get some background information on possible solutions before I go to make a sacrifice to the network gods. No point in abasing myself if it's not technically possible. :-)
EDIT: We do have the network infrastructure set up to allow directed broadcast, though figuring out the exact broadcast address since netmasks are not always /24 is another conundrum that I need to solve.
If you are on a local network that uses DHCP you might be able to look in the servers database to get the MAC of the last user with that address. In the future you could watch the network for ARP requests and cache the responses in some sort of table. You might also look at using RMON or SNMP to try and query the Address Tables on the switches and routers.
It should be noted that to use WoL across routers you either need to enable Directed Broadcasts or you need to have a relay server in the local segment.
Been a while since I played routers and swtiches but this might be a starting point for what to query using SNMP http://www.cisco.com/en/US/tech/tk648/tk362/technologies_tech_note09186a00801c9199.shtml
Use the following:
getmac /s destIp
To get the remote session Mac address.
I don't know if these might be helpful but take a look:
http://www.webdeveloper.com/forum/showthread.php?t=134120
http://www.qualitycodes.com/tutorial.php?articleid=19
You've said everything I can think of...
The source MAC address changes as a packet hops from device to device so unless the client is on the same subnet, the server won't be able to get the MAC address. (You would do it via ARP)
A signed java applet or activex control would be the easiest solution. It would be able to (almost passively) get all the networking info you need (IE doesn't even prompt to run a signed applet)
If you are fully aware of the network that is using the service then you could probably query a gateway's client-list via SNMP or CDP. You would be able to map out IP-Addresses to MAC addresses... but this is really vendor dependent (but common) and wouldn't be much better (imo) than having an applet.
Currently the application is using a Java 6 applet that allows me to extract both the hostname and the MAC address from the remote system. I don't like having this dependency on Java 6, but Snow Leopard and Windows both support it, so I can probably live with it.
On a related-front our networking folks approached me for some help with converting some existing code to ASP.NET. During the conversation I asked if they had live MAC address information (since they do port shutoffs based on suspicious network activity -- viruses/worms). Turns out they do and we may be able to leverage this project to get access to the information from the network database.
I don't think there is any way to accomplish this. When the IP packet goes via the first router the host's MAC information is lost (as you know MAC is only used in ethernet layer). If the router most close to your PC was capable of telling the remote MAC code to you, again it would only see the MAC of the next router between your PC and the "other end".
Start sacrificing.
There's no general way to do this in terms of the network unless you have no routers involved. With a router involved, you will never see the MAC address of the originating system.
This assumes that the originating system only ever has a single network interface, so has only a single MAC address.
In fact, are you even sure that your "magic packet" (whatever that is) will reach the system you want it to reach, through the routers? That sounds like a function the routers or other network infrastructure should be performing.
Mac address is only used on network segments, and is lost at each hop. Only IP is preserved for end-to-end - and even then the from ip address is rewritten when Natted. I guess my answer is, not possible unless everything is on the same network segment, or your routers are set up for proxy arp (which is not really realistic).
You can only get MAC entries in the ARP table for machines on the same network. If you connect to a machine via a router then you will only see the routers MAC address in the ARP table. So there is no way of knowing the foreign host’s MAC address unless it's a host on the same network (no routers involved).
And by the way there are many similar question already on SO.
if it's a windows system you can use NBTSTAT -A
this will return the netbios info and the IP is there
any Management system like SMS or Altiris will have this info
The DHCP server is a good idea
If it's local you can ping it and then quickly run ARP -a
look for the IP and the MAC will be there.
you might need to write a small batch file.
if you have access to the PC you can use WMI to access the info for the Nic with DHCP.
As said above we can get mac address from a known IP address if that host is in the same subnet. First ping that ip; then look at arp -a | grep and parse the string on nix* to get mac address.
We can issue system command from all programming languages standard API's and can parse the output to get mac address.Java api can ping an IP but I am not sure if we parse the ping output(some library can do it).
It would be better to avoid issuing system command and find an alternative solution as it is not really Platform Independent way of doing it.
Courtesy: Professor Saleem Bhatti
I have 2 network devices that talk to each other over Ethernet. I would like to sniff the traffic using Wireshark. But the devices are going through a switch. The switch routes the traffic to only the ports that need the data.
At another location I have a hub. All the traffic is repeated across all the ports.
Is there a way to tell the switch to send the traffic down my port also?
EDIT: This is an unmanaged switch.
You might want to look into ARP spoofing.
http://en.wikipedia.org/wiki/ARP_poisoning
Since this is an unmanaged switch, the only way that I can think of is to temporarily put a hub between the switch and one of the devices you want to monitor, then plug a laptop into that hub to do the monitoring. The laptop should now see all traffic between the device and the switch.
This is pretty easy since you can do it at the location of one of the devices. You just need a hub, two more lengths of CAT cable and the computer you are using to monitor with.
The switch may have a management interface that lets you do that. Be warned that if you do, you'll wreck performance on the switch since everything attached to it will now have to deal with collisions.
If the switch is a managed switch, it likely has a mode to act like a hub. Just be careful not to leave it like that.
Some will also have ways to mirror ports and such as well. You need to find out what kind of switch it is.
RE Edit: If it is unmanaged, then you are boned. Use a hub, a managed switch or run wireshark on the computer(s) affected.
You could try a port redirector, like this one. You would configure one device to talk to your computer instead of the other device, and the redirector will send the data to the real target. There are several programs like this out there, or you could write your own.