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I have a Raspberry Pi 3 (Model B). I want to use it as a terminal to operate a CNC machine as it has a Web Interface (Duet WiFi). I just need something with a browser and internet connection.

I first installed Raspbian and later on Ubuntu Mate, and both OSes show the same problem. They connect the first time and I can browse a little bit. From the second time on, the Raspberry Pi can see the WiFi and connect to it, but it does not load anything. Not even the CNC machine connected to the same WiFi router.

I have absolutely no experience with Raspberry Pis other than following Installation Instructions made for Dummies. So I don‘t know how to address it. Obviously I googled it, but none of the solutions helped me. I'm using a 3A power supply to be sure it has the juice it needs.

The Raspberry Pi is located literally 4 meters away from the router. I have another Raspberry Pi connected to that router and running Octoprint and it's never failed me, so I am assuming the router is not at fault here.

Any help would be appreciated. Thanks in advance.

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  • I don't understand. So when Rpi is connected to WiFi network through router, your browser cannot find the CNC website. But can you at least browse to other websites? If yes, then it is the CNC website's problem. And if WiFi is not working for now, can you try wired Ethernet?
    – tlfong01
    Sep 24, 2019 at 9:17
  • The Rpi won‘t connect to either the CNC nor any other websites. The CNC is not the problem. I have another Duet WiFI (the controller for the CNC) on another machine and it works flawlessly
    – Marcal
    Sep 24, 2019 at 12:23
  • Thank you for your clarification. I am not knowledgeable enough to offer more help. But I do think @Ljm Dullaart has good suggestions.
    – tlfong01
    Sep 24, 2019 at 13:07
  • With 4 meters from the router it is physically no problem to connect the RasPi wired with an ethernet cable for testing. Is this possible? Please address me with @Ingo, otherwise I won't see your reply.
    – Ingo
    Sep 25, 2019 at 18:48

1 Answer 1

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It could be anything, from the CNC machine not accepting connections, to more than one DHCP server on the network and a defective Pi.

Some debugging help for connectivity.

First, you must be sure that the WiFi is connected. Use ifconfig for that. The output will give you something like:

wlan0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.178.3  netmask 255.255.255.0  broadcast 192.168.178.255

(with some more lines). If your wlan0 does not have an IP address, your WiFi connection is lost. You could test if a wired connection stays up. Or you will need to debug the Wifi.

Can you reach the network? In general, there is a default gateway on a network segment that will answer to pings. Find out what is your default gateway with netstat -rn: 

Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
0.0.0.0         192.168.178.1   0.0.0.0         UG        0 0          0 wlan0
192.168.178.0   0.0.0.0         255.255.255.0   U         0 0          0 wlan0

Here, the destination 0.0.0.0 has the gateway 192.168.178.1. If you ping -c3 192.168.178.1, you will get a reply if your pi can reach the network. If you can't ping the default gateway, you will need to go back to debugging the connectivity. Note, that in some corporate networks, paranoid network engineers have disabled ping replies. But that should not be of concern here.

So, you are now at the network level be able to reach your CNC machine. Ping it to be sure.

If you reach this stage, your problem lies in the upper layers. That means it is an application problem.

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  • Your debugging help is very newbie friendly.
    – tlfong01
    Sep 24, 2019 at 11:57
  • I followed the steps you laid out for me and I could get the gateway address as 10.0.0.1 which is the WiFi router (i.e. this is the address I type in the browser to get into my router web interface). None of the 3 packages sent were transmitted and it reports „Host Unreachable“ also 3 times...
    – Marcal
    Sep 24, 2019 at 12:36

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