Tag Archives: linux

Transfer UDP over SSH

When you want to transfer some UDP protocol from a remote server not directly accessible from your local host you can use a combination of SSH and socat to make this communication possible.

The application case is, as an exemple, a SNMP communication with a server in a DMZ to get metrics in a local area dashboard. Like in this exemple.

You have an intermediate host where SSH is accessible you can use as a gateway.

1- on the local host (on the left side), create a SSH tunnel with a TCP port forwarding (here 10000).

ssh -L 10000:localhost:10000 **gateway_host_ip**

2- on the gateway host, route the traffic received from the port we have previously associated to the UDP target host:port

socat tcp4-listen:10000,reuseaddr,fork UDP:**target_host_ip**:**udp_port**

3 – on the local host, route the traffic received from the given UDP port to the previously associated TCP port for tunnelling

socat -T15 udp4-recvfrom:**udp_port**,reuseaddr,fork tcp:localhost:10000

That’s it.

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Pi Day – Sigma Lambda Pi

Sigma Lambda Pi is the perfect thing to talk about on the 3/14 Pi day!

This crazy machine is a 16 Raspberry Pi-4 cluster in a 2U server rack, set to execute FaaS (Function as a Service) with a green-it approach. Don’t make a dream of Raspberry-Pi high performance demonstration, you will be disappointed and it’s not the purpose of this project. This is not a commercial product, the objective of the company who made it, was research, team building and team skills improvement. This has been made by friends of my, working at Be|ys, a team of 9 people, under the lead of Christophe Prugnaud. They made a demo of it during the Clermont’Tech Api Hour #46, the video will be soon accessible.

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Fongwah S9 NFC Reader

I’m actually working on a device using a NFC chip from ST. Unfortunately, this chip is not using the ISO-14443 norms but the less usual ISO-15693 one. As a consequence the NFC reader I had were not compatible with this norms. I found a solution (there are not a lot) in Amazon to covert this need. The Fongwah S9 NFC Reader. I made this post to share my test experience of this device.

Precision: this is not a post made for Fongwah, I really have to crash my head on this device and the purpose of this post is to save your time. The fondwah S9 is a nice tool with a multi-language (on top of C library) SDK but it is delivered with no easy documentations, broken links and no reference on ISO-15693 support… I was a bit disappointed once the box opened.

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RF433 – Raspberry PI GPIO kernel driver for interrupt management

You may have read some of my post about RF433 and Raspberry PI. Basically with RPI 1, I was using wiringPi interrupt handler to manage the RF433 decoding. The problem is that with RPI2 and RPI B+ the delay to take an interrupt that was becomes unpredictable. And the timing constraints are not respected. As a consequence part of the messages are loss because for these delay.

One of the solution (the software one) is to be more efficient to proceed the interrupts and the way to do this is to compile a kernel driver for directly handling the interrupts. This is what this post is about. This comes to complete the RFRPI code and associated hardware. A complete source code and software for using it is on the rfrpi bitbucket repository.

Challenge of the coming days : write a kernel driver to manage interruption quicker on a raspberry pi 2. I’m happy to find a lot of example on Internet and in particular this one, that is really looking like what I’m trying to do. This post is describing all the step needed to do this.

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Configure internal Lan & OpenVPN on Azure

If you want to create a company like infrastruture on Azure you could expect to create a VPN to have a secured access to it and have an internal lan to protect you servers against external access. Basically the system provides all that you need but, as usual in the closed world of MicroSoft. The VPN server based on SSTP protocol sound hard and not documented to be used with MacOsX or Linux.

I’ll describe in this post how I fixed this issue par using an OpenVpn gateway server.

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