Develop Reference

Unable to connect to Scylladb in Docker using C# driver

I have created a single node ScyllaDB in docker, which is up and running, and below is my docker-compose commands:
version: "3"
services:
scylla-node1:
container_name: scylla-node1
image: scylladb/scylla
restart: always
command: --smp 2 --memory 1500M --broadcast-rpc-address 127.0.0.1 --listen-address 0.0.0.0
ports:
- 9042:9050
networks:
web:
networks:
web:
driver: bridge
Reading the documentation for Scylla it recommends using the DataStax C# Driver for Apache Cassandra. So, I have used this in my solution. Following the basic examples, I am struggling to get it work. Thus,
var cluster = Cluster.Builder()
.AddContactPoints("0.0.0.0")
.Build();
var session = cluster.Connect("sample_keyspace");
When the code reaches the Connect command it throws the following error
Cassandra.NoHostAvailableException: 'All hosts tried for query failed (tried 0.0.0.0:9042: SocketException 'The requested address is not valid in its context.')'
Firstly, I can connect to Scylla through the CSQL Utility and can create a Keyspace and then run a query to confirm that the Keyspace has been created.
Is this a problem with C# Driver or am I doing something wrong?

This looks like a networking issue to me because your Docker container doesn't appear to be configured correctly.
The problem is that the C# driver (your application) is not able to connect to the container because there is no network connectivity. That is what this exception means:
Cassandra.NoHostAvailableException: 'All hosts tried for query failed (tried 0.0.0.0:9042: \
SocketException 'The requested address is not valid in its context.')'
I assume "CSQL utility" is a typo. The reason you are able to connect using cqlsh is because you are most likely connecting with:
$ docker exec -it scylla-node1 cqlsh
which isn't the same as connecting remotely. To be fair I'm making an assumption as you didn't provide details.
You've configured the container with --broadcast-rpc-address 127.0.0.1 so it will only listen for client connections on localhost. This means that you can't use 0.0.0.0 as the contact point.
I've also noted that you've mapped the container port 9050 to host port 9042:
ports:
- 9042:9050
By default, Cassandra listens for client connections on port 9042, not 9050. If nothing is listening on port 9050, there's nothing for the driver to connect to and will also lead to NoHostAvailableException. Cheers!

ASP.NET Core disable HTTPS

I have a dockerized ASP.NET Core app that I'm trying to run locally under Linux (Fedora 33). I'd like to disable HTTPS so I don't have to deal with constant certificate errors.
To do this I simply disabled the HTTPS redirect feature which is included by default, however the app then wasn't responding to any HTTP requests at all.
I managed to get the dev version of the app to run on HTTP by explicitly configuring Kestrel in Startup.cs:
webBuilder.UseKestrel(options => {
options.ListenAnyIP(5000);
});
However, it isn't working for the Production version of the app. Whenever I send a request to http://0.0.0.0:5000, I just get a curl: (56) Recv failure: Connection reset by peer error.
Running netstat -ap in the container doesn't show the app as being bound to the port:
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 localhost:46825 0.0.0.0:* LISTEN -
udp 0 0 localhost:36022 0.0.0.0:* -
Active UNIX domain sockets (servers and established)
Proto RefCnt Flags Type State I-Node PID/Program name Path
unix 2 [ ACC ] STREAM LISTENING 27739639 1/dotnet /tmp/dotnet-diagnostic-1-3889474-socket
During startup the app also doesn't display the same information that I would normally expect, e.g. the following from another of my dockerized ASP.NET Core apps that does use HTTPS:
web-prod_1 | Hosting environment: Production
web-prod_1 | Content root path: /app
web-prod_1 | Now listening on: https://[::]:443
web-prod_1 | Now listening on: http://[::]:80
web-prod_1 | Application started. Press Ctrl+C to shut down.
The app doesn't print any of this on start, which is a little concerning.
I'd really appreciate any help with this, I've tried just about everything I can think of and I'm pulling my hair out over it.
EDIT
The cause of this was unrelated to HTTPS - a HostedService with a StartAsync that didn't terminate was being added in Startup.cs. Somehow this was stopping the rest of the app from starting, but only in production builds. Moving the AddHostedService call to Program.cs resolved the issue.

But is the container engine actually starting with the flags to bind the container and hosts ports? Conection reset means that the port is closed and actively rejecting connection.
You mention you did a netstat from inside the container, can you run another one from the host while the container is running? I like to use netstat -plnt
If your container is exposing the correct ports to the OS you should see it and be able to reach it at localhost:port, here I have a mysql proxy exposing 3306
❯ sudo netstat -plnt
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
1/init
tcp6 0 0 :::3306 :::* LISTEN 300988/containers-r
Which I had to specify the port binding when launching it (depending on your container engine this is done in different flags/options)
docker run -ti -p 3306:3306 eu.gcr.io/xxx-xx/svc-xx-xx-tests

1st cheek by other browser
or
cheek blocking antivirus or firewall of your PC may interrupted it.
then
change the port number before by cheeking the ip and port number by ip scanner.
as you now when you need change http to https need SSL certificate , so set disable option Tools->option->environment->webbrowsers

Cannot connect to Mysql service from c# front-end in kubernetes

I have a kubernetes cluster with front end as C# console application written in .NET Core and a backend Mysql db. Both of these applications are deployed as deployments in kubernetes in different pods. I have also created a mysql service to be able to connect with Mysql db. But, I can't seem to connect to mysql server from .NET core console app to kubernetes Mysql service. However, I can pretty much connect with Mysql pod using the IP address from the console app.
I will try my best to describe the situation here.
$ kubectl -n radiomicsapp get pods -o wide
NAME READY STATUS RESTARTS AGE IP NODE
anonymizer-pod-586548ddd9-kv8cj 2/2 Running 0 21s 10.244.0.187 aks-agentpool-35971152-1
mysql-744bfb878c-scwz9 1/1 Running 0 19h 10.244.1.244 aks-agentpool-35971152-2
$ kubectl -n abcapp get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
mysql ClusterIP 10.0.54.120 <none> 3306/TCP 104d
If I use IP address from the pod (10.244.1.244) to connect with db, it works. However, if I use IP address (10.0.54.120) from mysql service, it throws
Error: Unable to connect to any of the specified MySQL hosts.
Since, the IP address of the mysql pod changes whenever the pod is restarted/recreated, I will have to change the db connection string in my anonymizer console app, I created a mysql service with type ClusterIP as given below:
apiVersion: v1
kind: Service
metadata:
name: mysql
namespace: abcapp
labels:
app: abc
spec:
type: ClusterIP
ports:
- name: mysql
port: 3306
protocol: TCP
targetPort: 3306
selector:
app: abc
Also, my anonymizer pod, mysql pod as well as mysql service are all in the same namespace.
Any help would be much appreciated. Thanks for taking your time.

You have to use the service name on your code and leave kube-dns to handle the IP resolution for you to be sure your code works no matter if the pod is recreated or moved and it takes a different IP address during the process.
From another answer is easy to extrapolate an approximate example
How to connect to MySQL Database?
string connstring = string.Format("Server=mysql; database={0}; UID=UserName; password=your password", databaseName);
connection = new MySqlConnection(connstring);
Notice that only need to put on the Server mysql

Cannot get Mosquitto to Allow Connection from Outside Local Network

I have Linux Ubuntu 18.04 laptop, and I installed the Mosquitto MQTT broker there. On my Windows 10 laptop, I am running a C# application written in Visual Studio 2013 that uses the M2Mqtt Libraries.
If I connect via the localhost, everything is fine. I start up the Mosquitto server, connect via the C# application, subscribe to a topic, and then can send messages back and forth all day long.
But when I try to connect through the internet address, I consistently get a uPLibrary.Networking.M2Mqtt.Exceptions.MqttConnectionException:
"No connection could be made because the target machine actively
refused it 95.XXX.XXX.134:1883" error. (The address there is what I got via "WhatsmyIP")
Here's what I have done so far:
First, I went to my router, which is a TP-LINK AC1200. I set the port to forward to the local IP address of the Linux box.
Then I went to my Linux box and used ufw to enable port 1833 and enable the firewall
From there I have tried everything I can think of -- I've run Mosquitto with the port declared at the command line, I have changed the conf file to say:
Listener 1883 0.0.0.0
and
Listener 1883 192.168.0.144
I have removed the port assignment and listener assignment entirely (since that is its default anyway) and always I get the same result.
I downloaded 2 different utilities -- one on an android phone and one is an app available from Windows store, and I cannot connect with either of them, either. The Android phone simply will not connect (it is not on the same network so localhost is not an option) and the other app will connect locally, but not when I change to the internet address.
I get the sense I'm just missing one small thing, but I can't figure out what it is. There are other stackoverflow questions that show the same error, but they don't help me.
If it matters, the actual C# code that is being run is:
try
{
System.Security.Cryptography.X509Certificates.X509Certificate caCert = null;
Boolean useSecureProtocol = false;
int OpenPort = 1883;
// external IP address
String PublicIPAddress = "95.XXX.XXX.134";
// local IP address
String LocalIPAddress = "192.168.0.144";
System.Net.IPAddress ipaddress = System.Net.IPAddress.Parse(PublicIPAddress);
client = new MqttClient(ipaddress, OpenPort, useSecureProtocol, caCert, MqttSslProtocols.TLSv1_0);
// certificate and Protocol are irrelevant because security set to false??
}
catch (System.Net.Sockets.SocketException SException )
{
string SEX = SException.Message;
}
* * *
try
{
Byte retVal = client.Connect(ClientId);
}
catch (uPLibrary.Networking.M2Mqtt.Exceptions.MqttConnectionException ex)
{
string m = ex.Message;
}
Config File: conf.d (which I run explicitly with the -C option)
# Place your local configuration in /etc/mosquitto/conf.d/
#
# A full description of the configuration file is at
# /usr/share/doc/mosquitto/examples/mosquitto.conf.example
#
pid_file /var/run/mosquitto.pid
persistence true
persistence_location /var/lib/mosquitto/
log_dest file /home/mark_admin/mosquitto.log
include_dir /etc/mosquitto/conf.d
As I said, I have changed it and tried many things:
Listener 1883 192.168.0.144
Listener 1883 0.0.0.0
Listener 1883
And none of the above. Just left it blank. None of them worked.

I'm posting this as an answer so I can give more detail in case anyone stumbles upon this in the future.
Setting up the MOSQUITTO MQTT Server in Ubuntu 18.04 is actually not hard, but the steps are important.
Step 1: Install Mosquitto Software
sudo apt-add-repository ppa:mosquitto-dev/mosquitto-ppa
sudo apt-get update
sudo apt-get install mosquitto
Step 2: Open Port 1883 and start firewall
sudo ufw allow 1883
sudo ufw enable
Step 3: Verify Mosquitto is not already running
pgrep mosquitto
[Note, if any number shows, that is the PID of an already running Mosquitto. You can just kill it. Also, you can try: sudo service mosquitto stop]
Step 4: Start Mosquitto with verbose option
mosquitto -v
[Note: This starts Mosquitto without using any config file. It echos connection and status information to the screen. Easiest for quick debugging.]
Step 5: Check connectivity using local host
Go to your client machine (in my case a Windows 10 laptop) and run the MQTT client, connecting to the local address of the Linux Mosquitto server (in my case 192.168.0.144). You should be able to connect. In fact, you can do this step before you even open the firewall, since this is all on the local network, the firewall rules are irrelevant at this point. Until next step which is...
Step 6: Check Connectivity using web tool
use either: www.yougetsignal.com/tools/open-ports/ or
https://canyouseeme.org/
[NOTE: You will not get an OPEN state UNLESS THE MOSQUITTO BROKER IS RUNNING]
Step 7: If Port Shows Closed When coming In from Internet (ie not localhost)
Here's where I got tripped up. In my case, I have a Verizon Modem that ALSO has a firewall (because it has a router). I have my own wireless router, a tp-link Archer C1200, that I have plugged into the Fios Modem/Router. I started by putting the port forwarding in the tp-link. But that firewall comes after the Fios firewall so I needed to go to the first wall and do the port forward there.
And this is the second thing that is tricky. All of the online how-to's said I should forward port 1883 to the local IP address of my Linux Server, which in my case was 192.168.0.144. But that was not correct in my case. The Archer C1200 was actually the device that I needed to forward to -- it handled the correct distribution from there. It had an address of 192.168.0.152 assigned to it from the Verizon router. I still have both forwardings in place (ie the Fios and the tp-link) and my guess is that I need them both.
Now all pathways are open, you can follow the other Mosquitto instructions regarding logging, config files, Daemons, etc.
Hope this saves someone some time down the road!

Telnet to the RabbitMQ Stomp adapter just hung

I am using RabbitMQ server 3.5.6 on windows 8.1 and Windows 7 x64.
I have to access the Stomp Adapter embedded with the RabbitMQ Server.
So i have configured it from https://www.rabbitmq.com/stomp.html
it shows that it is successfully enabled and configured the rabbitmq_stomp.
After doing this i have restarted my computer and try to telnet to the localhost 61613 (the default socket of the rabbitmq_stomp) and it just hung in there saying connecting.
The RabbitMQ server log says:
=INFO REPORT==== 4-Dec-2015::17:53:29 ===
accepting STOMP connection <0.327.0> ([::1]:49397 -> [::1]:61613)
what did i do wrong? any help would be appreciated.

I find out a way to test the STOMP with RabbitMQ, you can issue the following command to test it. The solution here is by using nc, I didn't find a way using telnet under Windows though.
echo -e 'CONNECT\naccept-version:1.0,1.1,1.2\n\n\0' | nc -q10 127.0.0.1 61613
Normally the client should send the first byte in that protocal, usually something like CONNECT\naccept-version:1.0,1.1,1.2\nhost:yourstomp, needs a null byte , in this case is Ctrl-#, at the end to terminate, so that would be easier to send via echo -e or similar.