The OT-2 communicates with the Opentrons App via standard HTTP and WebSockets over a network connection. The OT-2 can connect via two available networking interfaces:
- USB, via an internal USB-to-Ethernet adapter
Over both interfaces, the robot “advertises” itself to the Opentrons App via multicast DNS (mDNS, also known as Bonjour) so that the app can know which IP address to reach out to for a given robot.
The OT-2 can connect to WiFi networks with the following types of security:
Open (no security)
- Note: captive portal logins are not supported
WPA2 with EAP / 802.1x (e.g. enterprise and eduroam networks)
- EAP-TTLS with TLS
- EAP-TTLS with MS-CHAP v2
- EAP-TTLS with MD5
- EAP-PEAP with MS-CHAP v2
Please see our “Connecting your OT-2 to Wi-Fi” support document for instructions on how to connect your robot to a wireless network.
USB (Ethernet) requirements
When you plug your robot’s USB connection into your computer, a new USB-to-Ethernet networking adapter will appear in your computer’s network adapter list. The robot will self-assign itself a link-local IPv4 address for this adapter.
Please make sure your computer is also set up to self-assign a link-local IPv4 address. Windows and macOS should do this automatically, but on Linux you may have to set this up manually or install Avahi.
Unless your computer happens to have avahi installed, you will probably need to set the robot’s network interface to “Link-Local” explicitly.
Assuming that you cannot connect to a wired robot:
- Open the “Settings” application
- Navigate to “Network”
- Find the wired network adapter that is either “Connecting” (and failing to connect) or “Off”
- When you plugged in the robot, after a few minutes you may have already seen a notification for a failure to connect to network
- Click the gear icon and navigate to the IPv4 tab
- Set “IPv4 Method” to “Link-Local Only”
After a few seconds, the interface should self-assign a link-local IP address. Try opening the app to see if the robot appears.
By default, macOS self-assigns a link-local IP address to any adapter that does not receive a DHCP-provided IP address. To ensure your computer can access the wired robot, confirm that the adapter interface is configured with its default settings, which should look something like this:
The robot’s adapter will appear in the “Network” panel of “System Preferences” as something like “USB 10/100 LAN”
- “Configure IPv4” must be set to its default value of “Using DHCP”
- “IP Address” should have been populated with something in the `169.254` range
- “Subnet Mask” should be “255.255.0.0”
If for some reason the IP address isn’t self-assigning to link-local, you can manually refresh the IP:
- Click “Advanced”
- In the “TCP/IP” tab, click “Renew DHCP Lease”
- Click OK
Note: If all else fails, restarting your computer can often help.
By default, Windows self-assigns a link-local IP address to any adapter that does not receive a DHCP-provided IP address. To ensure your computer can access the wired robot, confirm that the adapter interface is configured with its default settings:
Go to “Control Panel” > “Network and Internet” > “Network Connections”
You should see an Ethernet adapter of type “Realtek USB FE Family Controller”. Right click on the adapter and click “Properties”. Once the properties are open, select “Internet Protocol Version 4 (TCP/IPv4)” and click “Properties”:
Under “General”, ensure “Obtain an IP address automatically” and “Obtain DNS server address automatically” are selected. Under “Alternate Configuration”, ensure “Automatic private IP address” is selected.
If your computer is still unable to communicate with your robot via the USB to Ethernet adapter, you may try releasing the adapter’s IP address via the command line to try to force it to pick up a new link-local address. Open the Command Prompt, type “ipconfig /all” to find your adapter’s name (look for Realtek USB again), and then enter ‘ipconfig /release “Adapter name”’ (Probably “Ethernet 2” or something similar).
Note: If all else fails, restarting your computer often helps.
To ensure the app can successfully find and talk to your robot, your router’s firewall and your computer’s firewall need to allow the following connections:
- mDNS discovery: UDP on port 5353
- Robot communication: TCP on port 31950