AWS Ubuntu SSH suddenly disconnects and can't reconnect - amazon-web-services

I created a new micro instance of Ubuntu Server 20.04 and connected with putty successfully. I did some work on the server, setting up nginx and other things. Out of the blue, my connection got disconnected and then when I try to reconnect using putty, I get a connection timeout. I spent a while trying to figure out what was wrong and gave up, so I created a new instance and did some work, and after about an hour, the same thing happened, disconnected and can't reconnect with a timeout error. What could cause this? How do I even troubleshoot?

So in the instructions for configuring NGINX on Ubuntu it gives instructions for configuring UFW, and says I needed to allow HTTP and HTTPS but made no mention of SSH, so I allowed SSH "ufw allow ssh" and then set ENABLED=yes in /etc/ufw/ufw.conf, and so far so good.

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Cannot reach react application via dns hosted on ec2

I just want to see my development working on an EC2, showing to some friends, and think in deploying it after all of the work is done, but react doesn't cooperate. :/
I did everything I always do.
Started a ubuntu server on EC2
applied a group with 3000/tcp opened in my instance
Installed all dependencies of my app, npm 11.1 and its packages via npm install.
npm started it
and...
Nope.. there is no "and"... just my tears over a bunch of attempts without reaching 3000/tcp via public ip and dns..
I even tested ping on it.. set ICMP echo request and response rules, tested and it worked, but when I try to reach the application by 3000/tcp port, nothing.
Does someone have any idea?
As an image talk more than a thousand words, there it is... My nighmare
PS: a curl on localhost:3000 inside the ec2 works just fine.. while
another curl outside the ec2 returns Connection Refused
Looks like the application is bound to localhost (127.0.0.1). Update your start property to include --host 0.0.0.0
Refer: https://github.com/webpack/webpack-dev-server/issues/147

Connecting to Could SQL from local machine via proxy

I am following these instructions to deploy a Django app on Google App Engine:
https://cloud.google.com/python/django/appengine
I have got as far as downloading the proxy .exe file (I am on a Windows machine) and connecting to it:
2019/01/08 16:14:08 Listening on 127.0.0.1:3306 for
[INSTANCE-NAME] 2019/01/08 16:14:08
Ready for new connections
When I try and create the Django migrations by running python manage.py createmigrations I see the connection received by the proxy file:
2019/01/08 16:15:06 New connection for
"[INSTANCE-NAME]"
However, after a couple of seconds pause I get this error:
2019/01/08 16:15:28 couldn't connect to
"[INSTANCE-NAME]": dial tcp
35.205.185.133:3307: connectex: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.
I have tried disabling my local firewall in case this was causing any issues, but the result is the same. I've also checked the username, password and Cloud SQL instance name, they are all correct.
What could be causing this error?

How to setup VirtualBox network property to make ClickHouse callable on default port 8123 from master OS?

I made VM Ubuntu 16.04 with one network adapter "network bridge" and second adapter "internal network". ClickHouse DBMS installed by default.
Test call within slave Ubuntu curl 'http://localhost:8123/' returns Ok.
But the same call from master Windows host returns nothing :(
Telnet and browser from master OS on http://assignedIP:8123 returns ERR_CONNECTION_REFUSED.
At the same time pings slave Ubintu from master OS and opposite are successful.
How to setup VM's network properly to be able to call ClickHouse on port 8123 from master OS?
Found it!
Have to change
<listen_host>::1</listen_host>
to
<listen_host>::</listen_host>
in /etc/clickhouse-server/config.xml
Could you please check Unbutu firewall status. If it is up, bring it down and try.

SSH tunnelling to a remote server with django

I'm trying to set up an SSH tunnel to access my server (currently an ubuntu 16.04 VM on Azure) to set up safe access to my django applications running on it.
I was able to imitate the production environment with Apache WSGI and it works pretty good but since I'm trying to develop the application I don't want to make it available to broader public right now - but to make it visible only for a bunch of people.
To the point: when I set up the ssh tunnel using putty on Windows 10 (8000 to localhost:8000) and I run http://localhost:8000/ I get the folowing error:
"Not Found HTTP Error 404. The requested resource is not found.".
How can I make it work? I run the server using manage.py runserver 0:8000.
I found somewhere that the error may be due to the fact that the application does not have access to ssh files, but I don't know whether that's the point here (or how to change it).
Regards,
Dominik
After hours of trying I was able to solve the problem.
First of all, I made sure putty connects to the server and creates the desired tunnel. To do that I right-clicked on the putty window (title bar) and clicked event log. I checked the log and found the following error:
Local port 8000 forwarding to localhost:8000 failed: Network error:
Permission denied
I was able to solve it by choosing other local port (9000 instead of 8000 in my instance).
Second of all, I edited the sshd_config file: sudo vi etc/ssh/sshd_config
and added these three lines:
AllowAgentForwarding yes
AllowTcpForwarding yes
GatewayPorts yes
I saved the file and restarted the ssh service:
sudo service ssh stop
sudo service ssh start
Now when I visit localhost:9000 everything works just fine.

Problems getting RabbitMQ and Django-Celery Running: Target Machine actively refused connection

I am trying to get Django-Celery running on my Django App. I cannot get the worker server to run. When I try I get the message: No Connection could be made because the target machine actively refused it
Here is what I have done so far. First, I installed the django celery package: http://pypi.python.org/pypi/django-celery
I can load it into python without problems. I also installed the RabbitMQ server per the windows install instructions: http://www.rabbitmq.com/install.html#windows
Starting the tutorials in pytho on the RabbitMQ site I saw the need to install pika: http://pypi.python.org/pypi/pika. It imports without any problems.
From there I start the RabbitMQ server by running this at the command line: rabbitmq-service start
I get the message back that Service RabbitMQ started
Here is where I start to have problems.
I attempted the first steps in django-celery: http://packages.python.org/django-celery/getting-started/first-steps-with-django.html and the "hello world" example on the rabbitMQ site: http://www.rabbitmq.com/tutorials/tutorial-one-python.html
In both cases I get the message: No Connection could be made because the target machine actively refused it
My first thought was that this sounded like a firewall problem. So I went into the windows 7 firewall and added inbound and outbound rules to open the local and remote ports 5672 and 5673 to TCP protocol, but I still get the same error message.
When I run rabbitmqctl status i get the message:
Error: unable to connect to node 'rabbit#hostname': nodedown
diagnostics:
- nodes and their ports on hostname: [{rabbitmqctl18856, 505031}]
Does that mean it that it is trying to operate on those ports? what about the default 5672?
Any suggestions?
UPDATE: This was actually a problem resulting from several failed rabbitmq installs conflicting with the latest installation. If you have to remove rabbitmq use the 'rabbitmq-service remove' command and not SC DELETE, which cause a lot of problems for me and I had to go in and clean up my windows registry file.
The nodedown error indicated by rabbitmqctl suggests that the server isn't running on that machine.
Try going though the steps in RabbitMQ's troubleshooting guide. In particular, pay close attention to the logs. Has the server crashed for some reason? Could you post the logs somewhere?