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Connection refused occured when I trying to connect to Redis that run in Docker in WSL2 (Ubuntu 18.04)

Never happened before, but today I upgrade Windows preview version, and an exception occured (Connection Refused: connect).
Redis runs in a Docker container and Docker runs in WSL2 (Ubuntu 18.04), and also there are a Mongodb database and a Mysql database running in docker.
I cannot connect to Mongodb(by Java) or Redis (by Jedit) but Mysql is well (by Navicat or Java).
Then, I write a simple java program with Jedis to connect to Redis, it works failed in Windows but successful in WSL2. And I also connect to Redis with telnet command, it works successful in Windows and WSL2.
Windows Version: 10.0.20175.1000, Insider Preview, Build 20175.re_prerelease.200717-1349
Linux in WSL2: Ubuntu 18.04
Docker Version: 19.03.8
Mongodb and Redis: latest
Mysql: 5.6
Jedis: 2.7.2
Exception in thread "main" redis.clients.jedis.exceptions.JedisConnectionException: java.net.ConnectException: Connection refused: connect
at redis.clients.jedis.Connection.connect(Connection.java:155)
at redis.clients.jedis.BinaryClient.connect(BinaryClient.java:83)
at redis.clients.jedis.Connection.sendCommand(Connection.java:94)
at redis.clients.jedis.BinaryClient.set(BinaryClient.java:100)
at redis.clients.jedis.Client.set(Client.java:29)
at redis.clients.jedis.Jedis.set(Jedis.java:65)
at com.ty.tissue.config.TissueConfig.main(TissueConfig.java:105)
Caused by: java.net.ConnectException: Connection refused: connect
at java.net.DualStackPlainSocketImpl.waitForConnect(Native Method)
at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:85)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
at java.net.Socket.connect(Socket.java:589)
at redis.clients.jedis.Connection.connect(Connection.java:149)
... 6 more
help me, thanks.

Netbeans Debugging with Tomcat Connection Refused

I am using Netbeans 8.2 with the Java EE Base 1.31.1 and EJB and EAR 1.27.1 plugins installed. I installed Tomcat 9.0.4 and added it as a server to Netbeans. Netbeans can successfully start the tomcat server and launch my web app, but it will not debug. When I attempt to debug my webapp, I get the following error in my webapp log:
ant -f /Users/jryan/JDev/SVN/trunk/Java/CollaborationServer -Dnb.internal.action.name=debug -Ddirectory.deployment.supported=true -DforceRedeploy=false -Dnb.wait.for.caches=true -Dbrowser.context=/Users/jryan/JDev/SVN/trunk/Java/CollaborationServer debug
init:
deps-module-jar:
deps-ear-jar:
deps-jar:
library-inclusion-in-archive:
library-inclusion-in-manifest:
compile:
compile-jsps:
debug:
Stopping Tomcat process...
Waiting for Tomcat...
Tomcat server stopped.
Starting Tomcat process...
Waiting for Tomcat...
Tomcat server started.
connect-debugger:
/Users/jryan/JDev/SVN/trunk/Java/CollaborationServer/nbproject/build-impl.xml:1206: The following error occurred while executing this line:
/Users/jryan/JDev/SVN/trunk/Java/CollaborationServer/nbproject/build-impl.xml:1216:
org.netbeans.api.debugger.jpda.DebuggerStartException: Connection refused (Connection refused)
at org.netbeans.modules.debugger.jpda.JPDADebuggerImpl.waitRunning(JPDADebuggerImpl.java:405)
at org.netbeans.modules.debugger.jpda.JPDADebuggerImpl.waitRunning(JPDADebuggerImpl.java:387)
at org.netbeans.api.debugger.jpda.JPDADebugger.attach(JPDADebugger.java:324)
at org.netbeans.modules.debugger.jpda.ant.JPDAConnect$1.run(JPDAConnect.java:235)
at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1443)
at org.netbeans.modules.openide.util.GlobalLookup.execute(GlobalLookup.java:68)
at org.openide.util.lookup.Lookups.executeWith(Lookups.java:303)
at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:2058)
Caused by: java.net.ConnectException: Connection refused (Connection refused)
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
at java.net.Socket.connect(Socket.java:589)
at com.sun.tools.jdi.SocketTransportService.attach(SocketTransportService.java:222)
at com.sun.tools.jdi.GenericAttachingConnector.attach(GenericAttachingConnector.java:116)
at com.sun.tools.jdi.SocketAttachingConnector.attach(SocketAttachingConnector.java:90)
at org.netbeans.api.debugger.jpda.AttachingDICookie.getVirtualMachine(AttachingDICookie.java:231)
at org.netbeans.modules.debugger.jpda.actions.StartActionProvider.doStartDebugger(StartActionProvider.java:188)
at org.netbeans.modules.debugger.jpda.actions.StartActionProvider.access$200(StartActionProvider.java:80)
at org.netbeans.modules.debugger.jpda.actions.StartActionProvider$1.run(StartActionProvider.java:165)
... 4 more
BUILD FAILED (total time: 7 seconds)
The tomcat log says Listening for transport dt_socket at address: 8000
And the Netbeans Debugger Console says:
Attaching to localhost:8000
Connection refused.
Does anyone know what is happening here, and what I can do to fix it?
Thanks!

Perhaps try adding the flags detailed in this Answer.
This is how we currently do it.

Oops. It turns out that I had commented out the 127.0.0.1 localhost entry in my /etc/hosts file. When I re-enabled localhost, it worked fine! And as an aside, I thought I had to comment out the default localhost line because I had another line in there for a locally hosted site I was testing, but according to this answer, there's no need to do that!

mongoDB, connection refused

Show my code
conf.set( "mongo.input.uri" , "mongodb://127.0.0.1/stackoverflow.mrtest" );
conf.set( "mongo.output.uri" , "mongodb://127.0.0.1/stackoverflow.mrtest_out2" );
the code runs without error when the host is localhost or 127.0.0.1. But when the host changed to my ip wlan0 192.168.1.102, it returned the following error
Cluster created with settings {hosts=[192.168.1.102:27017], mode=SINGLE, requiredClusterType=UNKNOWN, serverSelectionTimeout='30000 ms', maxWaitQueueSize=500}
Exception in monitor thread while connecting to server 192.168.1.102:27017
com.mongodb.MongoSocketOpenException: Exception opening socket
at com.mongodb.connection.SocketStream.open(SocketStream.java:63)
at com.mongodb.connection.InternalStreamConnection.open(InternalStreamConnection.java:114)
at com.mongodb.connection.DefaultServerMonitor$ServerMonitorRunnable.run(DefaultServerMonitor.java:127)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.net.ConnectException: connection refused
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
at java.net.Socket.connect(Socket.java:589)
at com.mongodb.connection.SocketStreamHelper.initialize(SocketStreamHelper.java:50)
at com.mongodb.connection.SocketStream.open(SocketStream.java:58)
... 3 more
I have open the port 27017.
sudo iptables -A INPUT -ptcp --dport 27017 -j ACCEPT
My OS is Ubuntu 14.04.
How should I fix it? Thank you!

By default MongoDB only binds to the loopback interface which makes it only accessible from localhost. To change that you need to edit this line in mongod.conf file;
# /etc/mongod.conf
# Listen to local interface only. Comment out to listen on all interfaces.
bind_ip = 127.0.0.1
you can change it to bind_ip = 127.0.0.1,192.168.1.102 to allow LAN and local connections or you can remove or comment out that line to allow all connections.
For more info : MongoDB – Allow remote access

There could be several reasons of it , which in short can be concluded as Your Application is unable to Communicate mongoDB service
1.Check your MongoDB using the same IP configured in your application.yml file,
If not then configure the same used by MongoDB:
spring:
profiles:
active: dev
---
spring:
profiles: dev
data:
mongodb:
host: localhost
port: 27017
Here i assumed my mongo running on localhost, and port 27017, so i configured accordingly.
Check whether your MongoDB service up and running , How to check ?
Execute following command in your terminal
sudo service mongodb status
<pre><code>
● mongodb.service - An object/document-oriented database
Loaded: loaded (/lib/systemd/system/mongodb.service; enabled; vendor preset: enabled)
Active: active (running) since Fri 2020-07-03 20:10:15 IST; 1min 54s ago
Docs: man:mongod(1)
Main PID: 14305 (mongod)
Tasks: 23 (limit: 4915)
CGroup: /system.slice/mongodb.service
└─14305 /usr/bin/mongod --unixSocketPrefix=/run/mongodb --config /etc/mongodb.conf</pre></code>
If Status not visible as active and running, you need to start/restart the service
sudo service mongodb restart

I was able to determine that it was an issue with the bind parameter in the /etc/mongod.conf. Instead of commenting it out I set it to 0.0.0.0 to all for remote access.
# network interfaces
net:
port: 27017
bindIp: 0.0.0.0

Exception: com.mongodb.MongoSocketOpenException: Exception opening socket
Solution:
Verify whether you have started "mongo daemon" or not.
Windows Terminal: mongod.exe
Linux Termina: mongod

If you're using Spring Boot and are following the Quick Start, make sure you put this configuration in your application.properties
spring.data.mongodb.uri=[YOUR_URI]

spark standalone cluster slave unable to connect slave to master

i have the bin for spark-1.6.0-bin-hadoop2.6 im having issue trying to connect the slave to the master
so far i have tried(on ubuntu 14.04 live usb):
apt-get purge and install openssh-client and server on both systems
I have stated explicitly the ip address of the master in the spark url for the worker
spark://< master ip>:7077 and also tried changing the SPARK_MASTER_IP in /conf/spark-env.sh the worker executes but the log has the following error
im assuming there must be some ssh setup involved but i have tried ssh-keygen and ssh-copy-id # it also doesnt give any reuslts
16/02/22 07:49:16 INFO Worker: Connecting to master 192.168.0.208:7077...
16/02/22 07:49:16 WARN Worker: Failed to connect to master 192.168.0.208:7077
java.io.IOException: Failed to connect to /192.168.0.208:7077
at org.apache.spark.network.client.TransportClientFactory.createClient(TransportClientFactory.java:216)
at org.apache.spark.network.client.TransportClientFactory.createClient(TransportClientFactory.java:167)
at org.apache.spark.rpc.netty.NettyRpcEnv.createClient(NettyRpcEnv.scala:200)
at org.apache.spark.rpc.netty.Outbox$$anon$1.call(Outbox.scala:187)
at org.apache.spark.rpc.netty.Outbox$$anon$1.call(Outbox.scala:183)
at java.util.concurrent.FutureTask.run(FutureTask.java:262)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.net.ConnectException: Connection refused: /192.168.0.208:7077
at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:740)
at io.netty.channel.socket.nio.NioSocketChannel.doFinishConnect(NioSocketChannel.java:224)
at io.netty.channel.nio.AbstractNioChannel$AbstractNioUnsafe.finishConnect(AbstractNioChannel.java:289)
at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:528)
at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:468)
at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:382)
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:354)
at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:111)
... 1 more
16/02/22 07:49:27 INFO Worker: Retrying connection to master (attempt # 2)
i am however able to open the master webUI by typing :8080 on my browser . i am also able to access the webUI of the slave from the master . im almost at the point of giving in so please helllppp.

Make sure that each master and worker has a firewall exception to allow connections for all other workers and masters.
Here's a simplified example from one of our master machines (master0):
$iptables -L
...
ACCEPT all -- worker0.company.com master0.company.com
ACCEPT all -- worker1.company.com master0.company.com
ACCEPT all -- master1.company.com master0.company.com
...
Of course you can also use IPs instead of hostnames.

What is wrong with this Java code for a RMI JMX connection?

What is wrong with this Java code for a RMI JMX connection? I am clearly not trying to connect to localhost but the error implies that I am. On the remote server, I enabled JMX options on port 1099 (no authentication).
Here is my groovy script:
import javax.management.remote.*;
JMXServiceURL u =
new JMXServiceURL("service:jmx:rmi://10.222.244.185:9999/jndi/rmi://10.222.244.185:1099/jmxrmi");
JMXConnector c = JMXConnectorFactory.connect(u);
And here is the error I get:
C:\Temp>groovy jmx.gv
Caught: java.io.IOException: Failed to retrieve RMIServer stub: javax.naming.ServiceUnavailableException [Root exception is java.rmi.ConnectException: Conn
ection refused to host: 10.222.244.185; nested exception is:
java.net.ConnectException: Connection refused: connect]
java.io.IOException: Failed to retrieve RMIServer stub: javax.naming.ServiceUnavailableException [Root exception is java.rmi.ConnectException: Connection r
efused to host: 10.222.244.185; nested exception is:
java.net.ConnectException: Connection refused: connect]
at jmx.run(jmx.gv:5)
Caused by: javax.naming.ServiceUnavailableException [Root exception is java.rmi.ConnectException: Connection refused to host: 10.222.244.185; nested except
ion is:
java.net.ConnectException: Connection refused: connect]
at com.sun.jndi.rmi.registry.RegistryContext.lookup(RegistryContext.java:101)
at com.sun.jndi.toolkit.url.GenericURLContext.lookup(GenericURLContext.java:185)
... 1 more
Caused by: java.rmi.ConnectException: Connection refused to host: 10.222.244.185; nested exception is:
java.net.ConnectException: Connection refused: connect
at com.sun.jndi.rmi.registry.RegistryContext.lookup(RegistryContext.java:97)
... 2 more
Caused by: java.net.ConnectException: Connection refused: connect
... 3 more

This is the famous java.rmi.server.hostname problem. Usually caused by /etc/hosts misconfiguration in some Linux distributions. 127.0.0.1 should map to localhost, and your real hostname should map to your real IP address. See item A.1 in the RMI FAQ for another solution.
EDIT: Now that you've edited the IP addresses in your question, it is more probable that the JMX service you are looking up simply isn't running at that IP address.

Somehow your code trying to connect to 127.0.0.1 instead of remote
Connection refused to host: 127.0.0.1; nested exception is:
I suspect the code you are executing is different from the code you have in question. Make sure what ever the code you have in question is being executed.

This is more of configurtion issue where you have to explicitly mention how are you going to access the stubs. Try setting jmxremote options through JVM args. Following options might resolve your issue. I tried same for my own project.
-Dcom.sun.management.jmxremote
-Dcom.sun.management.jmxremote.port=8091
-Dcom.sun.management.jmxremote.rmi.port=8091
-Dcom.sun.management.jmxremote.ssl=false
-Dcom.sun.management.jmxremote.authenticate=false