RPi Connects To iPhone hotspot, but Termius cannot ssh into RPi (Ubuntu 20.04 64-bit Server)

Question

I would like to be able to ssh into my RPi3B+ based robot (running Ubuntu 20.04 64-bit Server) when away from my home WiFi.

I have configured the bot to recognize either my home network or my iPhone hotspot network.

/etc/netplan/50-cloud-init.yaml:

network:
    ethernets:
        eth0:
            dhcp4: true
            optional: true
    version: 2
    wifis:
        wlan0:
            access-points:
                SSIDHOME:
                    password: pwhome
                SSIDHOTSPT:
                    password: pwhotspot
            dhcp4: true
            optional: false

I see that the bot successfully connects to the hotspot.

Launching Termius on the iPhone, I created a host with the hostname of the bot - "ROSbot".

Clicking on the bot in Termius:Hosts shows "(ROSbot:22) Username / Select Identity" dialog, to which I select the desired identity (username/password) on the bot.

Termius reports:

Connection could not be established:
Connecting...
Disconnected
Connection closed with error: unknown node or service

Looking in the /var/log/auth.log there are two sshd entries:

Oct  3 10:24:56 ROSbot sshd[1921]: Server listening on 0.0.0.0 port 22.
Oct  3 10:24:56 ROSbot sshd[1921]: Server listening on :: port 22.

but no successful or failed login attempts are listed like when I remote in when the bot is connected via my home WiFi:

Oct  3 10:41:48 ROSbot sshd[2319]: Accepted password for pi from XX.0.0.XXX port XYZ ssh2
Oct  3 10:41:48 ROSbot sshd[2319]: pam_unix(sshd:session): session opened for user pi by (uid=0)

Any ideas how to debug what is happening and get this to work?

Answer 1

Found a solution:

• install the iNet Pro app
• after bot connects to hotspot, run iNet Pro network scan to determine the bot IP
• Tell Termius the bot's hostname is that IP
• ssh to the bot, authorize the unknown key, and I'm in!

Answer 2

In the ensuing year the iNet Pro app stopped working to show the iPhone hotspot clients.

What I have found good is to create a service that uses text-to-speech to read the IP address at boot to an attached speaker on my robot.

This takes the form of /home/ubuntu/utils/ip_feedback.sh

$ more ip_feedback.sh 
#!bin/bash

# FILE:  ip_feedback.sh
# This script is run once at boot by ip_feedback.service

echo "starting"
COUNT=0
IPs=$(hostname --all-ip-addresses)
while [ -z "$IPs" ]
do
    echo "loop"
    sleep 1;
    IPs=$(hostname --all-ip-addresses)
    COUNT=$((COUNT+1))
    echo "count: "$COUNT > /home/ubuntu/ipcount
done

echo "done looping "

echo "count: "$COUNT > /home/ubuntu/ipcount

ifconfig wlan0 | grep 'inet ' | awk '{print $2}'  > /home/ubuntu/ip.number
read -r IP_NUMBER < /home/ubuntu/ip.number
echo $IP_NUMBER

# remove previous IP info
sudo rm /boot/*.assigned_ip &>/dev/null
# sudo rm /home/pi/Desktop/*.assigned_ip &>/dev/null

# remove previous Failed IP
FAILED=/home/ubuntu/failedIP
if test -f "$FAILED"; then
    sudo rm $FAILED &>/dev/null
fi
# sudo rm /home/pi/Desktop/failedIP &>/dev/null

if [ ! -z "$IP_NUMBER" ]
then
        echo "saving IP info"
        sudo bash -c "echo $IP_NUMBER > /boot/$IP_NUMBER.assigned_ip"
#       echo $IP_NUMBER > /home/ubuntu/Desktop/$IP_NUMBER.assigned_ip
        echo "IP info saved"

        su -c "espeak-ng 'WiFi IP'" pi
        su -c "espeak-ng $IP_NUMBER" pi
        su -c "espeak-ng repeating "  pi
        su -c "espeak-ng $IP_NUMBER" pi
else
#       espeak-ng "no IP number"
        echo "no IP number"
        echo "no IP" > /home/ubuntu/failedIP
#       echo "no IP" > /home/ubuntu/Desktop/failedIP

fi
echo "done with IP feedback"

and the service definition /etc/systemd/system/ip_feedback.service:

[Unit]
Description=IP Feedback on Boot
After=syslog.target network.target


[Service]
Type=simple
user=pi
WorkingDirectory=/home/ubuntu
ExecStart=/bin/bash /home/ubuntu/utils/ip_feedback.sh

[Install]
WantedBy=multi-user.target

and running the commands:

• chmod 777 ip_feedback.sh
• sudo systemctl daemon-reload
• sudo systemctl enable ip_feedback
• sudo service ip_feedback start

Now every boot announces the WiFi IP.