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Dexter Networking

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JamesNewton edited this page Oct 15, 2018 · 69 revisions

Table of contents:

Connection

Dexter has an RJ-45 connector for CAT5 Ethernet connection. Because of issues with the Linux stack, WiFi adapters are not supported (as of September 2018). Although Dexter does have the ability to connect directly to the internet via a CAT5 cable to a local router, the easiest way to connect from a PC is to simply connect that CAT5 cable directly between the network port on the PC and Dexter. This is perfectly acceptable and works very well. The network adapter on the PC should be configured to the 192.168.1. network.

IP Address

Fixed IP

Dexter normally defaults to 192.168.1.142 so any other address is fine for the PC adapter. The PC's wifi adapter can remain connected to local WiFi at the same time as long as it's assigned IP address is in the same subnet.

To enable both WiFi and CAT5 to Dexter when the WiFi local network isn't on 192.168.1.#: First, download PuTTY or other SSH software (see below for setup and use). Make a note of the local IP address assigned to the WiFi then disconnect from WiFI, CAT5 to Dexter, SSH into Dexter or use a Serial USB connection. At the command prompt: nano /etc/network/interfaces and edit the ip address to 192.168.#.142 where the # matches the network IP address. Ctrl+X to exit, and follow the prompts to save.

DHCP assigned

Some Dexters may have been configured to use DHCP, and so need to be CAT5 cabled to a router with a DHCP service, or to a network with a DHCP server, and it's IP address will be whatever is assigned by DHCP. Your computer configuration needn't change. You can log into your router and look at the connected devices to find it, or

  • Android or iOS Smartphone: Install and use the Fing app
    https://www.fing.io/
  • on Linux / Mac use arp -a. You may need to ping broadcast first. Or sudo apt-get nmap and then nmap -rP _ip_/24 where ip is your local network address. e.g. 192.168.1.1
  • on Windows, arp -a returns the ip address, but no machine names. Or you can download and install
    http://www.advanced-ip-scanner.com

If you don't have a CAT5 connection to the network, you can connect directly via CAT5 to your computer, after making some changes to Dexters networking. See Issue 37 for more information. You may need to use a Serial USB connection to gain access to make those changes.

To disable DHCP and return to a static IP address, connect to Dexter and at the command line, enter
nano /etc/network/interfaces
Then edit the file to change the iface eth0 line to replace dhcp with static. It should look like this:

iface eth0 inet static
    address 192.168.1.142

Shell Access via SSH

Once you are connected, you can shell into Dexter to update the firmware or do development in the onboard Linux OS, or just connect via DDE to develop and run jobs.

To SSH into Dexter, you will need an SSH client (e.g. PuTTY). Configure the IP address in the client software to Dexter's address, set the port to 22, and select SSH.

Username: root
password: klg

Hint: Under Connection / Data you can specify the "Auto-login username" so you don't have to type root every time.

X-Windows

It is also possible to run GUI applications via X11 Forwarding from PuTTY on an X-Windows Server such as X-Ming.

In PuTTY, under Connection / SSH / X11, check "Enable X11 forwarding", set the display location to localhost:0.0 then save that session.

Individual applications

You can just start XMing, then PuTTY in with the X- forwarding commands set, and it will start a big blank "desktop" window. Alt tab to see the Windows taskbar, and minimize the empty desktop (you can't close it) by right clicking the preview from the taskbar and selecting "Minimize". Then you can start "nautilus" from the command line, but use "nautilus &" to run it in the background. Navigate to the /srv/samba/share folder to work, or to the /usr/share/applications folder to launch other applications. You can "Bookmark" these folders for faster access. This is kind of nice, because the applications each run in their own window in Windows making it easy to arrange them.

Desktop / Command line

You can also start the standard Ubuntu desktop from PuTTY with the command: gnome-session --session=ubuntu-2d & But if you have multiple monitors, you may wish to configure XMing to use only one monitor. XMing comes with XLaunch which allows you to configure how XMing display things. On the first "Display settings" panel, select "One window" and then keep the defaults for the other panels. Save that configuration file and use it to launch XMing in the future.

Easy Desktop

But the easiest way to set up the full desktop is to use XLaunch to make a workable config file for XMing and then use that config to launch it.

  • On the first "Display settings" panel, select "One window", on display 0. That zero is port 6000. e.g. 1 would be port 6001. If you use the "...without titlebar" version, you can't move the window. You can still alt tab, but if you have multiple monitors, it's nice to be able to put it elsewhere. Click "Next"
  • On the "Session type" panel select "Start a program", click "Next"
  • On the "Start Program" panel set the "Start program" to gnome-session --session=ubuntu-2d and under "Run Remote" do "Using PuTTY" then put in the IP address of Dexter under "Connect to computer" and also put in root and klg as the user and pass. Click "Next"
  • Leave the Clipboard and other stuff as default. Click "Next"
  • On the last "Finish" panel, check "Include PuTTY Password as insecure plain text" and save the config.
  • It will automatically start when you hit the "Finish" button. It does take some time to start; ~10 seconds. In the future, you can just XLaunch your configuration file.

Once in the desktop, you can start the file manager and navigate to the /srv/samba/share folder to edit files, or to the /usr/share/applications folder to launch other applications. This works a bit faster than the standard Dash home. If you "Browse Network" you may be able to access local NAS or other Linux shares, but Windows shared folders probably won't appear.

The default background logo really slows things down, but you can get rid of it under System Settings / Appearance. A solid black color seems fastest.

Terminal is very nice looking, with colors, a clear font, and nice size. It's even nicer if you go into Edit / Profile Preferences and uncheck "Use the system fixed width font".

File Sharing

SAMBA

Dexter provides a SAMBA share and an sFTP service for transferring files back and forth, in addition to the socket connection for commands via DexRun. Access the share at \\<dexters-ip>\share. Some versions of Windows or some Firewalls may block access to this share. Apparently this is because it isn't password protected.

SFTP

You can also transfer files via the /usr/lib/openssh/sftp-server service but you will need to supply the same username and password. And you will need a client which supports sftp such as
https://winscp.net/eng/download.php
Or if you want to integrate SFTP support into the Windows Explorer, you might try:
http://www.swish-sftp.org
Once installed, just go to "Swish" in the address bar and "Add SFTP Connection"

If you wish to disable or reconfigure the sftp daemon, see the /etc/ssh folder. Note: SFTP is not at all related to FTP.

Internet access

You generally should NOT need to actually give Dexter access to the internet, but if you need that for some reason, you will need that CAT5 cable to run between Dexter and your Router. After a restart, Dexter should automatically connect and have internet access. You can test that with ping www.google.com (press Ctrl+C to stop). If it works, great! If not, here are some common errors and how to resolve them.

  • "Network is unreachable" There is no internet connection. Check that Dexter is on the same network as your router. E.g. If your local network is 192.168.0. you will need to edit the IP address in both Dexter and DDE. In Dexter, sudo nano /etc/network/interfacesand edit the IP there. In DDE, you will need to change the default address for your Dexter robot in the dde_init.js file in your documents dde_apps folder. e.g. persistent_set("default_dexter_ip_address", "192.168.0.142")

  • "Unknown host" The DNS system could not resolve the name to an IP address. Try ping 8.8.8.8 instead. If you CAN ping 8.8.8.8 but still have no DNS (e.g. ping www.google.com) fails, then try adding nameserver 8.8.8.8 to a file called /etc/resolvconf/resolv.conf.d/base e.g. sudo nano /etc/resolvconf/resolv.conf.d/base type in
    nameserver 8.8.8.8 save it, and then restart.

See also

To search the Wiki, use the main search box in the black bar at the top, then select WiKi to filter the results or go to https://github.com/HaddingtonDynamics/Dexter/search?type=Wikis&q= and then add your search terms to the end of the URL.

To report errors, or request additional data, please chat with us on discord and/or raise a new issue

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