Julia as a bridge between windows and raspberry pi

General Usage
1

Hello everyone,

I’m trying to create project that runs in raspberry pi and windows and I want that Julia works as a bridge between both platforms.
I will try to explain.
I run Julia in my raspberry pi in order to process some data and create some particular files. This part is ok.
Now, I want to from my windows machine get those files to be treated using for that julia.

I already created an ssh connection between raspberry and windows but what i need, and what i don’t know how to do, is a piece of code in julia that allows me to go to the location of my files in my raspberry pi and copy them to a specific location in my windows machine.

Do you have any idea how this can be done?
Thanks in advance.

2

OpenSSH for Windows

It sounds like you have an ssh connection setup, so I think you continue to use that. The key command line tool to use is either sftp or scp. I recommend scp.

Installing OpenSSH for Windows is pretty easy. Microsoft has OpenSSH as an Optional Feature of Windows now:

Once you have that you can run scp from julia as follows.

julia> run(`scp`)
usage: scp [-346BCpqrTv] [-c cipher] [-F ssh_config] [-i identity_file]
            [-J destination] [-l limit] [-o ssh_option] [-P port]
            [-S program] source ... target
ERROR: failed process: Process(`scp`, ProcessExited(1)) [1]

Above you can see scp printed some help messages. What you want to do is something like

run(`scp username@raspberry_pi.host.name:/path/on/rpi C:\\path\\to\\local\\windows\\folder`)

LibSSH2_jll

If you wanted to do this on hard mode, you could use LibSSH2_jll and call the libssh2 API. Here’s an example for the C function libssh2_version:

julia> using Pkg

julia> pkg"activate --temp"
  Activating new project at `C:\Users\username\AppData\Local\Temp\jl_0N2fUl`

julia> pkg"add LibSSH2_jll"
    Updating registry at `C:\Users\kittisopikulm\.julia\registries\General.toml`
   Resolving package versions...
    Updating `C:\Users\username\AppData\Local\Temp\jl_0N2fUl\Project.toml`
  [29816b5a] + LibSSH2_jll v1.10.2+0
    Updating `C:\Users\username\AppData\Local\Temp\jl_0N2fUl\Manifest.toml`
  [56f22d72] + Artifacts
  [8f399da3] + Libdl
  [29816b5a] + LibSSH2_jll v1.10.2+0
  [c8ffd9c3] + MbedTLS_jll v2.28.2+0

julia> using LibSSH2_jll

julia> version = ccall((:libssh2_version,LibSSH2_jll.libssh2_path), Cstring, (Cint,), 0)
Cstring(0x000000006eabc3a0)

julia> unsafe_string(version)
"1.10.0"

See the following documentation about how to call C from Julia.

3

Hello @mkitti ,
I tryied the first option but Im getting the following error:

error
error1079×302 79.9 KB

What am I doing wrong?
Thank you in advance.

4

Note how I have \\ instead of \. This is because Julia regards the \ as an escape character.

Alternatively, you might consider using raw strings.

raw_str_path = raw"C:\Users\Username\Documents"
run(`scp rduarte@raspberrypi:/media $raw_str_path`)
5

Hi @mkitti
I just tried but the result remains

erro2
erro21081×362 87.7 KB

Do you have any idea why?
Thanks

6

It looks like you have a space in your folder name. This is a common cause for headaches and why I usually avoid spaces in file or directory names.

Try putting quotes around the paths.

Scp seems to think C is a host. I’m not sure why.

Can you confirm where you got ssh and scp from?

7

Hello @mkitti
I tried already without space and I get the same error.
To do: ssh my.raspberypi.ip.adress -l rduarte
I installed windows server through the following link:

For the scp I just typed the lines you wrote in the first post.
I’m really new on this, sorry if I miss some point.
Thanks

8

The problem is that scp is confused by C:\.... It thinks anything before the colon should be a hostname and it cannot find a host called C.

You might need to use quotes or d
or some alternative way to provide the path.

Try some variants of the following:

  • scp rduarte@rapsberrypi:/some/path "C:\\User\\Duarte\\Desktop"
  • scp rduarte@rapsberrypi:/some/path "C:/User/Duarte/Desktop"
  • scp rduarte@rapsberrypi:/some/path "C/User/Duarte/Desktop"

Maybe cd first and then try the following. The . means to copy it to the current directory.

cd(raw"C:\User\Duarte\Desktop")
run(`scp rduarte@rapsberrypi:/some/path .`)
9

If you want to have a shared filesystem between a R PI (Linux) and Windows you have many choices.
A very easy one is to use MobaXterm which has a built in graphical SFTP browser/transport utility

10

Other choices are creating an NFS share on the RPI and mounting that on Windows
Or you could use a CIFS share on either Windows or RPI and use Samba on RPI

You say you have an ssh connection availalbe. There are ssh based filesystems
SSHFS: How to Mount Remote File Systems Over SSH | phoenixNAP KB.

Please contact me if you want some help setting this up.

11

Thank you @johnh but this is not the kind of solution i’m looking for.
I what to pass files between raspberry and windows. Let’s say, when using windows, through an ssh connection I want to open julia in raspberrypi and then copy some files to my windows.
Thanks anyway.

12

Hello @mkitti,
Still not working.
Can you describe me what should I do to have a succefull scp connection between both os?
Maybe is there the error.
Thank you

13

@rduarte That is exactly how the SFTP browser works in MobaXterm.
Please install MobaXterm on your Windows laptop and try it.

14

What’s the current error? Is it changing at all?

I would expect this to create a different error than the ones you have been encountering.

cd(raw"C:\User\Duarte\Desktop")
run(`scp rduarte@rapsberrypi:/some/path .`)

Have you tried opening up Cmd.exe or Powershell.exe and executing the commands directly there?

15

Hello @mkitti
The error I getting now is:
erro3

16

Is it important that this should happen from inside Julia, and from running a single command, perhaps inside a larger workflow? Or is it okay if the file transfer happens in the end, possibly requiring user input, more like a seperate step?

17

Hello @TheLateKronos
Yes, I need that happens from inside Julia.
Thanks

18

I would first try do debug this outside of julia. You say that you have ssh working. I assume that is from powershell or something like that. So go to powershell:

ssh <username>@<raspberrypi>

should get you into the raspberry pi (with <username> and <raspberrypi> of course replaced by the appropriate values). There running touch somefile will create a file on your pi. Exiting the raspberry pi, you should then be able to do:

scp <username>@<raspberrypi>:somefile ./

If not then there is something wrong. If it works, but asks for a password, you will probably first have to set up loging in using keys; as typing in passwords from julia will be impractical. For that see, for example, How To Configure SSH Key-Based Authentication on a Linux Server | DigitalOcean. If that works, then running the same commands from julia should also work.

19

It probably is that directory does not exist. Specifically, are you sure the path is “User” not “Users” with an “s”?

20

Hello @djvanderlaan
I was able to connect to raspberry and create the “somefile” on it. However, when I try to do the scp (outside julia) i get the following message:
scp: .:not a regular file
Thanks