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We have an Automatic Weather Station. I connected my PC using an ethernet cable to it directly. I accessed the AWS using the IP 192.168.1.115 and changed the IP to some other class fixed IP. After two months the AWS has some problem. Now I want to access but I don't remember the IP address. How can I know the address?

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  • Hi, may I know what's the OS version of your PC? And do you remember the hostname of the AWS?
    – Sunny
    Dec 14, 2020 at 9:32
  • Hello, I have windows 10 enterprise installed. sorry, I don't remember the hostname. Dec 15, 2020 at 10:14

2 Answers 2

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On Windows, you can use arp -a and arp -av commands in command prompt to see all MAC<>IP mappings OS knows about, which will include the weather station if it sends some outgoing requests, like, for example, checks for software updates.

If it's silent though, and just waits for incoming requests, you'll may have to scan the network. Disconnect the internet before doing so, otherwise you might get locked out at provider (sometimes ISP ToS denies scanning).

There's nmap port for Windows, but it will require pcap drivers which have their own problems. Maybe start with something simplier, like Angry IP Scanner.

If IP of the station is outside of your PC's subnet, it might still not respond to TCP and UDP, and even ARP might get filtered, so you might have to extend your IP mask to something like 128.0.0.0 before scanning, and switch IP to another half of address space (just add or substract 128 to first number, for example, 192.168.1.5 → 64.168.1.5) before doing another scan. Switching IP might reset ARP, so check ARP table before doing this.

After scanning one or the other half of address space, station should at least appear in the ARP table even if it would not respond. Then reduce mask again and change IP of your PC to get into same subnet with the station, if you want to access it by TCP or UDP.

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You have multiple options to find the device on your network. The simplest approach would be to check the ARP table of another machine in the same LAN. On a linux machine, you can run arp -a.

In a different way, you can access your DHCP server (which is often just your router) and check the DHCP leases. Depending on the firmware of your router it might not show since you said that the IP address was fixed on the device.

Finally, you can discover devices in your network by probing or by using a discovery protocol. For example, you can check your network using nmap by running nmap -sP 192.168.1.0/24. You will need to carefully use the right prefix but it may be possible that the former is already correct since many homegrade router use a /24 prefix as a DHCP pool. Alternatively you can use mDNS to do this, for example by running avahi-browse -a.

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  • thanks. There is no router between my LAPTOP and the AWS. PC is connected directly to the AWS through the ethernet cable. Dec 12, 2020 at 16:33

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