Working around name-resolution problems for your OctoPrint-based 3D printer
OctoPrint is the amazing web interface for controlling 3D printers.
Bonjour is the hostname-broadcasting protocol which is used by OctoPrint so that anyone using an OSX-based computer can refer to their printer by its hostname.
ARP is a protocol for caching network adapter addresses versus their bound IP addresses.
DNS is the UNIX/Linux way of turning a hostname like
octopi.localinto an IP address.
WINS is the Microsoft way of turning a hostname into an IP address, treating it as if it were a NETBIOS hostname.
It appears that most Windows- and Linux-based users can't easily get to their OctoPrint printer and resort to using the IP address of that printer in order to connect via their browser.
The current wisdom is to simply: "install iTunes". Behind-the-scenes, this will also install the Bonjour name-resolution service and suddenly, it "just works". Unfortunately, this then inserts the Bonjour service into the Microsoft Windows setup and I can tell you from years' of experience as an I.T. Manager that this causes other problems for the user and they're too numerous to list.
I can confirm that Microsoft Windows (without iTunes) and Ubuntu cannot by default see an OctoPrint installation unless you use the IP address.
At a DOS or Terminal prompt, the standard PING command will broadcast on your local network and can place the OctoPrint's hostname into something called your ARP cache.
$ ping octopi.local.
PING octopi.local. (192.168.0.20) 56(84) bytes of data.
64 bytes from 192.168.0.20: icmp_seq=1 ttl=64 time=5.79 ms
...
Once this has succeeded, the Windows- or Linux-based user may then just open their browser and try again, using the hostname http://octopi.local and this should work until the next reboot of either workstation or printer.
It looks like this will stay cached for some time. Even after clearing the arp cache and rebooting, the browser itself also appears to be caching the DNS lookup as well so that's good news.
On a Windows-based computer and opening a cmd shell as Administrator, it's easy enough to edit the c:/windows/system32/drivers/etc/hosts file to add an entry for your computer but you would need to know its IP address first (editing for your printer's address):
192.168.1.20 octopi octopi.local
The proper way to do something like this is to get the Raspberry Pi 3 (or similar hosting computer) to broadcast its NETBIOS name, making Windows computers happier.
Samba is a royalty-free Linux package that allows computers to behave like Microsoft servers.
# It's important to run this next command before any attempt to update using apt-get later
$ sudo apt-get update
# Save a copy of your existing configuration file; you can always revert without ill effect
$ sudo cp /etc/samba/smb.conf /etc/samba/smb.conf.save
$ sudo apt-get install samba samba-common-bin
Now it will be necessary to edit the Samba configuration file, find the [global] section and add these lines.
$ sudo nano /etc/samba/smb.conf
[global]
workgroup = WORKGROUP
wins support = yes
netbios name=octopi
server string=OctoPrint on Raspbian
Having saved the file and exited (Ctrl-O, Enter, Ctrl-X), now parse it to verify that SMB likes what you did.
$ sudo testparm /etc/samba/smb.conf
Assuming that it's happy, now reboot to load those changes.
$ sudo reboot
To verify that your OctoPrint is now broadcasting, in Finder, press Cmd-K and then the Browse button. Although it appears here, we didn't share any folders so you can drill into it. This should suffice for testing the NETBIOS broadcast, though.
Perhaps the best way to test this is to try visiting http://octopi/ from your browser, noting the absence of .local as would normally be seen in these URLs.
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