flask server on raspberry pi stopped responding - python

I set up a flask server on my raspberry pi and set up a crontab to start the server on reboot. It was working fine for a while, for the past couple of days it stopped responding even after I rebooted the pi.
It seems like that the server is running because when I ssh in and try to run another server it says that the address is already in use.
Any ideas why my server is not responding anymore?
also, this may or may not be related but when I typed crontab -e I got the following error:
/tmp/crontab.Qqy98c: No space left on device
Creation of temporary crontab file failed - aborting

Address is already in use error indicates that some process is occupying the host/port that your Flask application is trying to use.
To resolve this problem, find out which processes are running on that port, then kill them. For example, if you use the default setting of port 5000, you can do the following in the terminal:
lsof -i:5000
This will show you the process that's running on port 5000 -- Take note of the process id. Let's say it's 12345 for example.
kill 12345
This should free up the address, allowing the Flask application to launch normally.
The error No space left on device Creation of temporary crontab file failed should be somewhat self-explanatory. If you're running so low on file space, you should strongly consider clearing up space. Otherwise, you're bound to run into all kinds of problems.

Related

Git bash "Watching for file changes with StatReloader" stuck and never loads

I have setup a Django project on a virtual environment on my PC. When using the command
python manage.py runserver 0.0.0.0:8000
Bit Bash stops doing anything and I have to end the program to start over. I have waited several minutes and when I end the session, a dialogue says:
Processes are running in session:
WPID PID COMMAND
14904 1534 c:\Users\mine\AppData\Loca
Close anyway?
I have looked at every related question to this and tried every solution but I cannot get this to work, on or off the virtual environment.
Not sure if this applies, but I also noticed that in my task manager, python3.9.exe appears twice when trying to start the server. The status says running, and the PIDs are different numbers.
This is because something already running on port 8000. You can run the Django server by hosting on another port like 8080 but, you can also kill the already running task on the port. Follow the link to know how exactly you can kill any running process.
It is highly likely that another application is running using the port 8000. Try running the server using another port, say 8088 and share if the same issue persists.
To run on specific port kill all pids which is showing you on Git bash
(ps -ef)... kill them using (kill -9 pid_no)... then run your runserver command.
Ex:
ps -ef
kill -9 123
I ended up paying someone to fix this. Here is the conversation I had with the person who found the issue. Hope this helps someone out there.
Also, I noticed sometimes it still does freeze up on the watching for file changes with StateReloader until I go the browser and type in http://localhost:8000/. Once I do that the rest of the text loads and my browser shows The install worked successfully! Congratulations!
it works, what did you do?
- We have existing processes on port 8000.I think, you had the server running and kept trying over and over. So, I killed process using 8000 port.
- Next, I run Django project again.
- So, now it's working well.
ok. Can you tell me what you did at the start to make it work? Or was it always working?
- I started git bash session again when I started. Maybe git bash session had problems.
But this was going on for a day, I restarted the computer several times and restarted git bash. Same issue.
You must have done something.
- Sorry, I didn't do anything except restart git bash
how did you restart it?
- right click top of window, select NEW
How do I turn server off?
- press Ctrl + C
- And you didn't quit the server exactly before. Maybe you closed git bash directly and server was still live
- So, we had many 8000 ports.
Ok. How can I see what is on that port now?
- You can use this cli
- netstat -ano | findstr :<PORT>
- We don't have running 8000 port now.
I have never found solutions to this problem even with killing ports, changing port etc.
It never display the following part:
Starting development server at http://127.0.0.1:8000/
However, when I use the Git Bash terminal include into vscode, it displays the url.
Terminal > New Terminal > then:
Result :
python manage.py runserver 127.0.0.1:8080

TCP server (Python) on Raspberry Pi bootup results in error: Address already in use

I have a TCP server created on a Python script, I want to execute it on Raspberry Pi boot up. I have put the Python script in .bashrc and it executes on the boot up, but it displays the following error:
s.bind(('', 5555))
socket.error: [Errno 98] Address already in use
I have created a TCP client on Matlab and the communciation works perfectly. I can manually execute the server from Raspberry Pi 3 command line send/recv data and close the socket, but even after properly closing if I restart my Raspberry Pi, on boot up it still displays the error.
I have also tried s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR,1), but I still get the error. I dont want to manually change the port number every time, therefore any help would be appreciated.
This message occurs when you try to use a port number that is already in use.
Because you start the server process with your .bashrc file, an attempt will be made to start it when your system boots, when you start a new shell, or when you ssh into the system.
This article makes some suggestions about other ways you could use.
Note that when you see this message, it comes from repeated attempts to start your server, but the good news is you should still be able to connect to the server - the message does imply it's already running.

While running google app engine application I encountered Bind error? [duplicate]

I am trying to run a Python app in Google App Engine. The UI doesn't work so I tried using the command lines. I tried restarting my PC, I tried changing port with "dev_appserver.py --port=9999 ." but it still says Unable to bind localhost:8000:
raise BindError('Unable to bind %s:%s' % self.bind_addr)
google.appengine.tools.devappserver2.wsgi_server.BindError: Unable to bind localhost:8000
The app server starts two servers; one for your application, the other for the development console. It is that second server that is causing the problem here; it normally would be run on port 8000.
Change the ip address for the development console with the --admin_port switch:
dev_appserver.py --admin_port=9000
You may still want to change the port for the main application server too, of course.
Also see the command-line arguments documentation for dev_appserver.py.
It is possible some application is binding to your port in autostart event.
It's highly probable to be the same service you are trying to run. In that case try killing the process
ps -ef | grep 'process_name'
Use kill -9 'pid' to end the process.
A computer restart did it, closing google app engine launcher, restarting the computer then launching again did the trick...
terminate old terminal and start in new, its the easiest way I
could find
Being unable a port is usually a sign of one of two things:
You don't have permissions
Something is already running there.
You can try hitting the local port 8080 with your browser to see what is there, and kill it if it shouldn't be.
As for permissions - only look for this afterwards. Presuming you are in windows (you didn't specify this), then you should be able to bind this as a normal user.
As for the command line - have you tried replacing the "=" with a space - I've seen both forms in documentation for app-engine.
dev_appserver.py --port 9999 .

Python process suspends on SSH logout after nohup/screen

I have a remote server through Blue Host that's intended to run a server based on Twisted for Python. The only access I have to it is over SSH, so to keep Python running after I log out I tried using nohup python server.py & and screen -dm python server.py, getting the same results for each. Everything works fine until I log out of SSH - even though Python is running in the background as expected, once I've logged out, my client can no longer communicate with the server. The strange part is that if I log back in over SSH and check the running processes with ps aux, I see Python running and my client can successfully communicate with the server again. Even if I don't type anything at all once I log back in, everything works as expected. But, of course, as soon as I log back out, it's as if the server is gone.
I've contacted support for the hosting service in case this is some oddity on their end, but hopefully this is something that can be resolved on my end instead.
Edit: Looks like Blue Host doesn't want me doing server-y stuff without buying the VPS upgrade so it looks like that's the big problem.
Edit 2: Okay, so in case anybody ends up having a similar problem, here's what the main issue turned out to be. I was mistaken in my original description; I was able to connect to the server but I was getting kicked off immediately for what turned out to be a MySQL error. I guess trying to connect to a localhost database with no active connection somehow causes problems, so instead I changed the MySQL connection command to connect to my site's IP address instead, even though it was the same IP as the server. That seemed to do the trick in terms of my main issue.
Don't use this method to keep the server process running. Instead try using supervisor (apt-get install supervisor). It allows you to daemonize your process, and ability to stop/restart etc.
Here's a sample config entry (/etc/supervisor/supervisord.conf):
[program:my_server]
command=python /path/to/server/server.py
directory=/path/to/server/
autostart=true
autorestart=true
stdout_logfile=/var/log/server.log
stderr_logfile=/var/log/server_error.log
user=your_linux_user_name
After you edit your config, do
sudo service supervisor stop
sudo service supervisor start #need to do this - doing a `restart` doesn't reload the config file!
your server should now be running properly. You can manage its lifecycle via sudo supervisorctl

google compute engine connection keeps disconecting

I have an instance on google compute engine, connecting to it by terminal: gcutil ssh, on it I have several DJango servieces. I run the server using: python manage.py runserver 0.0.0.0:8000. the services are being called from an iPhone application IOS 6.1
the problem I'm facing is that every few minutes (between 10- 15) I'm getting disconnected and have to reconnect and run the server again.
Why is my server being disconnected and how can I keep the it running?
Try using supervisor.d. It sounds like for what your trying to do, supervisor can keep your process up and running. http://supervisord.org/
Here's an example conf:
[program:app]
process_name = app-%(process_num)s
command =python /home/ubuntu/production/current/app/src/app.py --port=%(process_num)s
# Increase numprocs to run multiple processes on different ports.
# Note that the chat demo won't actually work in that configuration
# because it assumes all listeners are in one process.
numprocs = 4
numprocs_start = 8000
This is for running multiple processes of the same program. Just change around the args and it should work for you.
SSH normally times out after a period of inactivity, and that may be what is happening here. If so, this article might be useful to help configure SSH to send a regular message so connections are less likely to be dropped.
However, the core issue is that you'd like software you started at the terminal to keep running even when you're logged out. Consider using screen or tmux to host your shell sessions. This will allow your shell software to run even when you are not connected, and for you to pick up right where you left off when you reconnect. Here is a nice getting started post about tmux.
Once you're ready for production, take a look at the Django deployment docs.

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