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Raspberry Pi network connections

When starting a Raspberry Pi with an AvNav image, the network connections for the Raspberry Pi are also controlled via AvNav functions.

This primarily concerns the connection from display devices (web browser) to the Raspberry Pi, but also the possibilities for connecting the Raspberry Pi to the Internet or an onboard (IP) network.

In addition to access via web browser, the images are also prepared for access via command line (SSH). Normally, this is not required, as all important functions can be controlled directly from within AvNav.

However, for troubleshooting or for further interventions or adjustments to the system, it is very useful to have such access to the system.

If the image has been configured for a local screen, you can work directly with a connected monitor and, if necessary, a keyboard and mouse.

However, you should still prepare one of the connections described below in this case – you might find them useful in error situations.

Connecting to the Raspberry Pi

In principle, you can connect to the Raspberry in several ways:

  1. via Ethernet cable
    This is done either by connecting to a router or switch or via a simple connection, e.g., directly to a laptop.
  2. via internal WLAN
    By default, the Pi creates an access point with the SSID chosen in the configuration. It appends a number to it. If you connect additional WLAN adapters, you can also create multiple access points.
  3. via USB from an Android device
    Modern Android devices usually have a "USB tethering" function, which can be used to share the WLAN or mobile connection via USB. Unfortunately, this usually only applies to devices with mobile data.
    You can also connect to the Pi via this path.
  4. Via another WLAN.
    This requires one of the other connection options first, as you have to set the access credentials. It also requires an additional WLAN adapter.

Connection via Ethernet cable

If you connect the Pi to a router (e.g., in a home network), it will receive an IP address from it. You can connect to the Pi using this address.
Since it is often tedious to find this address, the Pi announces itself in the network via mDNS (Bonjour, Avahi).
In this way, you can easily connect to AvNav, e.g., with a browser:

http://xxxx.local:8080

xxx is the hostname selected in the image configuration.
Access via SSH (under Windows, e.g., via putty) is also possible in this way – the access password for the user "pi" has already been set in the image configuration.

If you connect directly to a laptop using a network cable, the Pi will independently set up an IP address after some time. This can take 1...2 minutes. This belongs to the so-called "Automatic Private IP Addressing" range 169.254.x.x. Most desktop systems support this as well. On Linux, you may need to enable it explicitly.
So, if the laptop has also set up such an address on its Ethernet interface, a connection should work as described via xxxx.local.

If access via the xxx.local address does not work, you must try to determine the IP address of the Pi, e.g., via the administration of your home router or a suitable app.

Connection via the built-in WLAN

You can use the WLAN network created by the Raspberry. The SSID and password were defined in the "avnav.conf" file as described in the image configuration (with an appended number).

Here, too, you face the problem of having to find the IP address of the Pi first. As described for the Ethernet access, access via mDNS should also work here.

http://xxx.local

If that does not work, you can try the fixed IP addresses defined in the image configuration. The default address is 192.168.30.10.

http://192.168.30.10

This should load the main page of AvNav. It should also be possible to use xxxx.local if you want to connect to the Raspberry via SSH (e.g., via putty on Windows).

One limitation remains: Unfortunately, xxx.local does not work on Android devices. Therefore, it is recommended to use a tool there that can utilize mDNS – a BonjourBrowser. For iOS, there is a comparable tool – even if the entry "xxx.local" works in the browser there. You will find your Raspberry with the AvNav image in the browsers under the name "avnav-server". Typically, you will see a second entry "avnav" – behind this is the SignalK server on the Raspberry.
If you can see your Raspberry in the Bonjour browser, but calling the page fails, it may be due to a peculiarity of Android when, for example, an Internet connection is additionally active via mobile data. In this case, you should temporarily switch off mobile data.

As of version 1.12, the "Android Bonjour Browser App" also supports SSH. The AvNav image (as of 20220421) also announces its SSH access via mDNS. If you then install a suitable SSH client on Android (for example JuiceSSH), you can also connect to the Pi via SSH in this way. This is usually not very comfortable for normal work, but for an emergency, you can enter a few commands.

When connecting via SSH, the username is "pi". The user password was (hopefully) set in the "avnav.conf" file.

If the password set in the configuration does not work, you can try the default password again. It is "raspberry". Perhaps the avnav.conf was not saved correctly beforehand.
You can get a root shell with sudo -i.

Connection from Android via USB

For this, you need an Android device that supports USB tethering. This is usually recognizable in the connection settings. After you have connected the device to the Pi via USB, you must switch on USB tethering. This is usually switched off automatically when you disconnect the connection.
In addition to the possibility of connecting the Pi to the Internet this way, you can also access the Pi with the browser or via SSH. Since the IP address must be determined again here as well, I recommend installing the Bonjour Browser App again – see under WLAN. For SSH access, again JuiceSSH.

You can also access the Pi via this path if, for example, the WLAN is not working. In the Bonjour browser, you will find at least 2 http: addresses: Port 8080 for AvNav and Port 3000 for SignalK, plus (as of version 20220421) an SSH access.

Connection via another WLAN

If you have set up a WLAN connection to another network as described below, which requires a WLAN stick, you can enable access to the Pi via this network ("external access" during setup).

However, you should only do this in a protected network, e.g., in the network of your own LTE router. Under no circumstances should you allow this in a public WLAN – the access is not protected, and in principle, anyone from the network can access the Pi.

Once connected to the client network, you can access the Pi again as described under WLAN.

Connecting the Pi to the Internet

For some functions, e.g., for updating software, the Pi requires an Internet connection. This is, of course, not required for the basic navigation functions.

Before image version 20220421, it should be noted that the Pi does not automatically set its system time as long as no GPS is connected. This can lead to problems with many Internet access attempts.
As of version 20220421, the Pi automatically synchronizes its system time with the network (NTP) after a certain waiting period.

For the connection to the Internet, the following options are available:

  1. Ethernet connection to a router
  2. Connection via another WLAN
  3. Connection via an Android device connected via USB

The Pi basically makes its Internet connection available to connected devices via its own WLAN.

Connection via Ethernet cable

Here, the Pi is connected to a router via an Ethernet cable.
There is nothing further to set up on the Pi; this should happen automatically.
On some Pi3 models, it may happen that a network cable connected only after the booting process is not recognized correctly. In this case, restart the Pi with the network cable connected.

Connection via another WLAN

An additional WLAN adapter (USB stick) is required for this. Please check compatibility with the Pi beforehand – e.g., here.

Via

 -> ->

you can call up the Wifi dialog.

Connection via an Android device connected via USB

As already described for access, you can connect an Android device with USB tethering. Internally, a network interface usb0 is created.
The Pi can also access the Internet via this.

This can be a simple option if you only need access temporarily and do not have an additional WLAN adapter available.
If you were connected to the Internet in another way before, it may be that the Pi only really uses the USB connection after a restart.

Attention: Switch USB tethering on the Android device back on, it is normally switched off when the Pi is restarted.

Technical details

A NetworkManager is used for network configuration on the Raspberry. The package avnav-raspi-network provides basic configurations that ensure the Ethernet interface retrieves its IP via DHCP and a hotspot is set up on the internal Wifi interface. Some parameters can be adjusted for the images. In addition, a firewall is set up with firewalld so that Ethernet and hotspot are in a "trusted zone" – and a potentially additional Wifi connection is either also in this zone depending on the configuration (externalAccess enabled) or in a separate "public zone".

For most actions, however, command-line access should not be necessary. For updates, use the pre-installed update plugin.