Raspberry Pi Forums

knute

In debian I entered: sudo ufw default deny . I don't know if that blocks outgoing or not but it is not required and if it blocks outgoing you are going to have all sorts of issues. And ftp uploading and downloading just works. As you now know there are two types of FTP, passive and active. I have f...

knute

thesisPi20 wrote: ↑
Fri May 22, 2020 6:15 pm
Hi all,

As the title says, I need to create a system with multiple Raspberry Pis that the Pis can send simple socket messages among them. Do you have any suggestion how I can start this?

Are you talking messages as in data acq/dist or text messages for humans?

knute

You don't want to open a port range. You want the firewall to take care of it for you. What you need to do is add the following to the end of /etc/ufw/before.rules: *raw :PREROUTING ACCEPT [0:0] -A PREROUTING -p tcp --dport 21 -j CT --helper ftp COMMIT That will make inbound passive FTP work. You on...

knute

Well I have a couple of questions: Are there more rules in UFW than you posted? Are your problems with outgoing FTP or incoming? And a couple of observations: Your rules seem too complex for a simple installation. There is a fault in UFW that prevents inbound passive FTP from working correctly. If t...

knute

Did you get it running? If not, post your code and I'll take a look.

knute

For embedded Java take a look at bell-sw.com. For IDEs you are on your own

.

knute

Take a look at my website, pi.knutejohnson.com, there is a complete set of instructions to operate the camera and serve the image with apache.

knute

I have been found it is hard to use ArrayList in the multithreaded environment. I want a solution to use ArrayList in a multithreaded environment. There are many ways but it depends a lot on what your use case is. Here is the quote from the docs: "Note that this implementation is not synchronized. ...

knute

See post below.

knute

There is a problem with Pi 0s and 1s with newer Javas. There are four openjdks available in the repository, 8, 9, 10 and 11. 8, 9 and 10 will run on a Pi 0 if you install openjdk-?-jre-zero and use the -zero command line option. openjdk-8 also appears to run without that on a Pi 0. There is no openj...

knute

Não sei qual software foi usado para esse gráfico, mas esse tipo de coisa é muito fácil de fazer em Java.

knute

DougieLawson wrote: ↑
Mon Mar 02, 2020 5:58 pm
Add
Code: Select all
 dtoverlay=i2c-rtc,ds3231
to /boot/config.txt and your RTC will be recognised when you poweroff, connect it and reboot.

Dougie do you still need to kill off the fake-hwclock and modify /lib/udev/hwclock-set?

knute

So enabling CGI is very simple with current apache. You don't need to edit ANY files. Just run the command: sudo a2enmod cgid Next put your CGI files in the /usr/lib/cgi-bin directory. They need to be executable by www-data. That's it! I would guess that your 500 error is caused by some permission p...

knute

I have website1.com inside of "/var/www/website1.com/public_html/index.php" and I have website2.com inside of "/var/www/website2.com/public_html/index.php" "<VirtualHost *:80> ServerAdmin admin@Website1.com ServerName Website1.com ServerAlias www.Website1.com DocumentRoot /var/www/Website1/public_h...

knute

Two NICs? /etc/hosts has no 205. address?

You don't need the two Port ### lines if you have the ListenAddress lines with the same ports. I want to see ip a too.

knute

Post an SSCCE and I'll look at the problem for you.

knute

I've got a Pi2B with a USB WiFi dongle that hangs up every now and then. I originally thought it was the Pi dying but the WiFi dongle goes deaf. If I pull it out of it's socket and put it back my Pi is back up and running just fine. Is there a way to power cycle the USB ports with software so I can ...

knute

Anyhow. Which buffers did you change to what size? We've got about 200 NUCs running Xubuntu 18.04. We send them a lot of UDP datagrams. For those we created a file 80-sysctl.conf in /etc/sysctl.d. In that we put: net.core.rmem_max=4194304 This improved the lost packet situation for us. I've seen fo...

knute

AJ Hunter wrote: ↑
Wed Feb 05, 2020 10:20 am
Well i am basically going for a VoIP solution

Take a look at the intercom code I wrote for the Pi, http://knutejohnson/pi. It is basically VoIP. You could cludge up an old phone handset with a USB mic and speaker.

knute

Don't know if this will help you but we found that increasing the receive buffer size significantly reduced the number of lost UDP packets.

knute

I'm sorry, I really don't know anything about Maven or even what it does.

knute

That problem had me going for some time. The OpenJDK 11 in the repository won't run on a Pi 0 or 1. I think you can still install JDK 8 from the repository and get it to work but the best answer is to download the Zulu OpenJDK for Arm from azul.com. Azul has both a JDK 8 and JDK 11 available for the...

knute

You can't get it from the repository but you can download it from https://gluonhq.com/products/javafx/ or you can get a complete JDK from BellSoft, https://bell-sw.com/ with their version of JavaFX. They have three versions available, I like the full version that includes JavaFX and the DeviceIO API...

knute

creative-2008 wrote: ↑
Thu Jan 30, 2020 8:56 pm
What am I missing? Is it that I don't have the latest version of Raspbian, and I can't update Apache without updating that first.

Most likely. My Raspbian Buster is up to date and I have apache version 2.4.38.

knute

The permissions for apache can drive you crazy. The thing to remember is that apache runs as www-data and needs to be able to read HTML files. They can be owned by anybody as long as they are readable by www-data. Usually this means world readable. The directory /var/www/html is owned by root and of...

Search found 612 matches

Re: UFW is blocking my ftp traffic.

Re: Socket communication among multiple Raspberry Pis

Re: UFW is blocking my ftp traffic.

Re: UFW is blocking my ftp traffic.

Re: Running multithreaded application on RPi

Re: Remote Java IDE for Raspberry Zero, where to start?

Re: Turn the pi into a webcam

Re: How to use ArrayList in multi-threaded environment?

Re: How to use ArrayList in multi-threaded environment?

Re: Pi Zero w and Java

Re: GUI

Re: Will a real time clock be found/configured on a new OS install?

Re: Apache2 & CGI Setup

Re: Hosting Multiple Websites on RPi 4 - Help Needed

Re: Can't ssh into raspberry pi from internet unless 0.0.0.0 Listen address is in sshd_config

Re: Terminal printing over JavaFX application

USB WiFi hangs intermittently

Re: RPi4 - serious (UDP) network issues

Re: Building a small Raspberry Pi phone

Re: RPi4 - serious (UDP) network issues

Re: Install OpenJFX 13 on Raspberry Pi 3B and Raspbian

Re: How to install jre / jdk on RPi zero

Re: Install OpenJFX 13 on Raspberry Pi 3B and Raspbian

Re: Apache Update

Re: Apache2 website permissions???