Does "Connection Refused" and success of PING command means that RaspberryPi is connected?

Question

I would like to SSH into my RaspberryPi connected with Ethernet cable using Ubuntu OS.

I believe that the Pi device is indeed connected to my Laptop, because:

• after running

  ifconfig eth0
  

  command I get the result that

  inet addr:10.42.0.1
  

• Then running

  ping 10.42.0.1
  

  with the Ethernet cable plugged in I get such results:

  PING 10.42.0.1 (10.42.0.1) 56(84) bytes of data.
  64 bytes from 10.42.0.1: icmp_seq=1 ttl=64 time=0.031 ms
  64 bytes from 10.42.0.1: icmp_seq=2 ttl=64 time=0.030 ms
  ...
  6 packets transmitted, 6 received, 0% packet loss, time 4997ms
  

  whereas running the same command with PC and Pi disconnected the results are:

  PING 10.42.0.1 (10.42.0.1) 56(84) bytes of data.
  From 10.128.128.128 icmp_seq=1 Packet filtered
  From 10.128.128.128 icmp_seq=2 Packet filtered
  From 10.128.128.128 icmp_seq=3 Packet filtered
  3 packets transmitted, 0 received, +3 errors, 100% packet loss, time 2000ms
  

Finally, I want to connect SSH to the device by running the command:

sudo ssh [email protected]

which, when the cable is plugged in reports:

ssh: connect to host 10.42.0.1 port 22: Connection refused

whereas, when the cable is plugged off reports:

ssh: connect to host 10.42.0.1 port 22: No route to host

Do these results mean that there is a successfull connection between two devices (my laptop and RaspberryPi) and that they are actually able to communicate?

If yes, how to proceed to ssh from Laptop into RaspberryPi?

Some of the issues I thought of are:

• I am running incorrect command (i.e. it should be something different than

  sudo ssh [email protected]
  

• some firewall or antivirus blocks the connection

could it be one of these?

Answer 1

Connection refused likely indicates that the port is being blocked.

If you have access to the pi, you may want to check the iptables rules:

    iptables -L

Or to flush the current rules..

    iptables -F

It could also be that SSH has been configured to run on a different port, in which case you could use something like nmap to investigate.

By default Raspbian has SSH enabled on initial install, on port 22, so it could mean that SSH simply isn't running.

Answer 2

Silly thought perhaps: where are you executing your ifconfig eth0 command? It looks like you're running it on your laptop, in which case 10.42.0.1 is your laptop's ip address, and you are trying to ssh to yourself. You need to know the ip address of the Pi, and ssh to that. It doesn't really explain why the ping changes when the cable is disconnected though, so this may be a red herring.

Answer 3

Ok, so I finally managed to:

• 1) Connect RaspberryPi with laptop using crossover cable.
• 2) SSH into RaspberryPi and get virtual terminal on my Laptop.
• 3) Have Wifi on the virtual terminal.
• 4) Have Wifi on my PC, Linux OS.

Here are instructions that worked for me:

From PC go to networks tab (on the top right), then click Edit Connections. In Ethernet, click on Wired connection 1 (or however the cable connection will be called on your laptop), then click Edit.... Go to IPv4 settings and set Method to be Shared to other computers.

Now go back to Network Connections tab, find your Wi-fi connection, click Edit... go to IPv4 settings again and make sure that the Method is set to Automatic (DHCP).

Then connect your RaspberryPi and Laptop with crossover cable, and boot the RaspberryPi up. A message Connected to wired connection 1 might appear briefly on the top right corner.

Finally, open the terminal, type

ssh [email protected]

and hope that the terminal asks for a password. If you succeed up to here, the most of the work is done. Enter the RaspberryPi password (try raspberry if you don't know it) and you will get a virtual shell of RaspberryPi.

Checking that Wi-Fi connection has been established one can in the SSH'ed shell type

ping 8.8.8.8

to check for arriving packets. If that succeeds type

ping [SomeWebsiteName]

to check that DNS works.

If you failed to get "enter password" request, some of the problems can be:

• The /etc/network/interfaces files. My files are as follows.

  In Linux Laptop:

  auto lo
  iface lo inet loopback
  

  On Raspbian:

  # Note some lines might not be required
  
  auto lo
  iface lo inet loopback
  
  auto eth0
  allow-hotplug eth0
  iface eth0 inet manual
  
  auto wlan0
  allow-hotplug wlan0
  iface wlan0 inet manual
  wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf
  
  auto wlan1
  allow-hotplug wlan1
  iface wlan1 inet manual
  wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf
  

• ssh program is not installed.

• [email protected] does not detect the Pi's IP address.