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Java exception connecting to MySQL

SOLVED
The latest version of MySQL JDBC driver evidently attempts to create an SSL connection. The app which WORKED did NOT define javax.net.ssl.keystore (and other) values, so (I assume) it reverts to a non-SSL connection. The app which FAILED did define all of the keystore/certificate parameters and then the connection attempt failed - still not sure of exactly why, if someone could enlighten would appreciate. The exception thrown could also be more informative.
Anyway, adding "&useSSL=false&allowPublicKeyRetrieval=true" to the connection parameters works for both applications. (Although not a very good setup for any production app, can use for this POC!)
============= Original Posting Follows =========
This has had me stumped for a few days! AWS server (86_64), Fedora 29, Java 8 (1.8.0_201-b09), MySQL - all upgraded to the latest release. MySQL is running on the same server. Driver: com.mysql.cj.jdbc.Driver
Connection params: jdbc:mysql://172.31.10.222:3306?user=xxxx&password=xxxx. (IP is the AWS private IP for this server.)
Have 2 different utilities - separate 'main' routines, but all in the same JAR file. The first one works perfectly, the second one aborts with the stack pasted below. This is consistent over dozens of trials with minor variations.
The different main routines both use the 'connectToDB' method shown in the stack trace. Instrumented this to log all parameters and the class name of the driver in both cases and verified that they are identical.
Have already tried/verified:
Multiple Google searches of the same error
MySql is running and OK (connect thru another terminal window w no problem),
Same JAR used with all local code
Classpath is identical
Running under the same Linux user, using the same MySQL user/password
Verified the IP above (172.31.10.222)
Also changed the IP to 'localhost', 127.0.0.1, and a symbolic name from /etc/hosts
Added -Xmx2G to make sure not an OOM issue
These are 2 different 'main' methods, but don't do much more than load some properties (from the same property files) before trying to connect to the DB. Then they execute the same connectToDB routine.
Something in the context must be different! Hoping that someone here can at least provide some hints on where to look!
Thanks
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
at com.mysql.cj.jdbc.exceptions.SQLError.createCommunicationsException(SQLError.java:174)
at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:64)
at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:835)
at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:455)
at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:240)
at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:207)
at spc.tools.spcConnection.connectToDB(spcConnection.java:692)
at spc.tools.spcConnection.connectToLocalDB(spcConnection.java:1418)
at spc.tools.spcConnection.loadAllConnectionsOK(spcConnection.java:1112)
at spc.tools.spcConnection.initOneTime(spcConnection.java:1012)
at spc.tools.spcConnection.init(spcConnection.java:194)
at spc.ops.spcServerBase.environmentOK(spcServerBase.java:367)
at spc.ops.spcServerBase.environmentOK(spcServerBase.java:342)
at spc.run.daemon.spcDaemon.main(spcDaemon.java:1082)
Caused by: com.mysql.cj.exceptions.CJCommunicationsException: Communications link failure
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:61)
at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:105)
at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:151)
at com.mysql.cj.exceptions.ExceptionFactory.createCommunicationsException(ExceptionFactory.java:167)
at com.mysql.cj.protocol.a.NativeProtocol.negotiateSSLConnection(NativeProtocol.java:351)
at com.mysql.cj.protocol.a.NativeAuthenticationProvider.negotiateSSLConnection(NativeAuthenticationProvider.java:777)
at com.mysql.cj.protocol.a.NativeAuthenticationProvider.proceedHandshakeWithPluggableAuthentication(NativeAuthenticationProvider.java:486)
at com.mysql.cj.protocol.a.NativeAuthenticationProvider.connect(NativeAuthenticationProvider.java:202)
at com.mysql.cj.protocol.a.NativeProtocol.connect(NativeProtocol.java:1442)
at com.mysql.cj.NativeSession.connect(NativeSession.java:165)
at com.mysql.cj.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:955)
at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:825)
... 11 more
Caused by: java.net.SocketException: Broken pipe (Write failed)
at java.net.SocketOutputStream.socketWrite0(Native Method)
at java.net.SocketOutputStream.socketWrite(SocketOutputStream.java:111)
at java.net.SocketOutputStream.write(SocketOutputStream.java:155)
at sun.security.ssl.OutputRecord.writeBuffer(OutputRecord.java:431)
at sun.security.ssl.OutputRecord.write(OutputRecord.java:417)
at sun.security.ssl.SSLSocketImpl.writeRecordInternal(SSLSocketImpl.java:879)
at sun.security.ssl.SSLSocketImpl.writeRecord(SSLSocketImpl.java:850)
at sun.security.ssl.SSLSocketImpl.writeRecord(SSLSocketImpl.java:720)
at sun.security.ssl.Handshaker.sendChangeCipherSpec(Handshaker.java:1144)
at sun.security.ssl.ClientHandshaker.sendChangeCipherAndFinish(ClientHandshaker.java:1280)
at sun.security.ssl.ClientHandshaker.serverHelloDone(ClientHandshaker.java:1190)
at sun.security.ssl.ClientHandshaker.processMessage(ClientHandshaker.java:369)
at sun.security.ssl.Handshaker.processLoop(Handshaker.java:1037)
at sun.security.ssl.Handshaker.process_record(Handshaker.java:965)
at sun.security.ssl.SSLSocketImpl.readRecord(SSLSocketImpl.java:1064)
at sun.security.ssl.SSLSocketImpl.performInitialHandshake(SSLSocketImpl.java:1367)
at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:1395)
at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:1379)
at com.mysql.cj.protocol.ExportControlled.performTlsHandshake(ExportControlled.java:315)
====================================================== New Information =====
Here are the key lines from the connectToDB method (responding to comment below):
Driver dvr = (Driver)Class.forName(info.sDBDriver).newInstance();
if(dvr!=null) conn = dvr.connect(accessString(), null);
verified the expected driver and that accessString() returns the 'jdbc:mysql:...' string as above. The exception is thrown executing the 2nd line above.
Since the original post, put in code to run a 'netstat -ln' immediately before these lines and post the result to the log. This shows an active listener for port 3306.

It would be great if you can post connectToDB() method.
According to this sentence " The first one works perfectly, the second one aborts with the stack pasted below.", you must have closed the db connection in the first connectToDB() call.
So that second call is broken as the DB connection was terminated by first call.
The good way to setup is to use dependency injection for database object.
Hope this helps!

Spring boot mongo mongoSocketException

I am using spring boot for my rest api but I have a problem about mongo database. Application sometimes throws mongo socket exception and does not execute following codes, when endpoint which needs mongo operation is triggred. I assign true to value of socketkeepalive but it did bot solve my problem. How can I get rid of this problem and can you offer me spring boot mongo db configuration values that are suitable?
By the way, program is working properly. But sometimes it throws this exception.
Thanks
INFO org.mongodb.driver.cluster - Exception in monitor thread while connecting to server **.***.***.***:42015
com.mongodb.MongoSocketOpenException: Exception opening socket
at com.mongodb.connection.SocketStream.open(SocketStream.java:63)
at com.mongodb.connection.InternalStreamConnection.open(InternalStreamConnection.java:115)
at com.mongodb.connection.DefaultServerMonitor$ServerMonitorRunnable.run(DefaultServerMonitor.java:127)
at java.lang.Thread.run(Thread.java:748)
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.mongodb.connection.SocketStreamHelper.initialize(SocketStreamHelper.java:57)
at com.mongodb.connection.SocketStream.open(SocketStream.java:58)
... 3 common frames omitted

Spring Boot has a feature called "auto configuration". In this case, as soon as the Mongo driver is detected on the classpath, the MongoAutoConfiguration is activated with default values, which point to localhost:27017. If you don't want that behaviour, you can now either configure the properties for MongoDB (see http://docs.spring.io/spring-boot/docs/current/reference/htmlsingle/#boot-features-mongodb for valid property keys) or disable the MongoAutoConfiguration:
#SpringBootApplication(exclude = {MongoAutoConfiguration.class, MongoDataAutoConfiguration.class})
Spring boot throws this exception when Mongo DB is not running. Please make sure that Mongodb is running. It got resolved for me after starting Mongo DB.
you can check if mongoDB is running on 27017 is running or not. use this code in your terminal
netstat -plntu
And Please show me your configurations file or properties file.

Got the same issue while running mongo inside a docker stack and i just missed the port mapping from 27017 (external) to 27017 (internal), so applying
ports:
- 27017:27017
to my docker-compose.yml file worked for me.

Java org.neo4j.driver.v1 Unable to connect to Neo4j 3.3.2

I have a neo4j database set up which I've logged into via the browser and properly set up the password:
The following python code WORKS:
>>> from neo4j.v1 import GraphDatabase, basic_auth
>>> driver = GraphDatabase.driver("bolt://localhost:7687", auth=("neo4j", "pass"))
However when I try connecting with Java (org.neo4j.driver:neo4j-java-driver:1.4.4):
Driver driver = GraphDatabase.driver( "bolt://localhost:7687", AuthTokens.basic("neo4j", "pass") );
I get a constant connection refused:
org.neo4j.driver.v1.exceptions.ServiceUnavailableException: Unable to connect to localhost:7687, ensure the database is running and that there is a working network connection to it.
...
Caused by: java.net.ConnectException: Connection refused
This leads to be believe that there is some kind of authentication issue going on (wrong password?) but that obviously isn't the case since I am connecting successfully via Python.

Connecting Application to OpenShift MongoDB

I had a MongoDB on MongoLab, which I was using with my Android Application and everything was just fine.
But well, they decided to upgrade the MongoDB version to 3.0.x and now I’m not able to connect again because the java driver 3.0 don’t seem to work very well on Android. We can see some discussion about the situation here: mongodb 3.x driver Android compatibility
Then I decided to try OpenShift, which has version 2.4 of MongoDB.
But I’m not being able to connect to the database like I use to do with MongoLab. I feel like I might be misunderstanding the purpose of OpenShift.
Caused by: java.net.ConnectException: Connection refused: connect
[...]
Exception in thread "main" com.mongodb.MongoTimeoutException: Timed out after 30000 ms while waiting for a server that matches ReadPreferenceServerSelector{readPreference=primary}. Client view of cluster state is {type=UNKNOWN, servers=[{address=127.XX.XXX.X:27017, type=UNKNOWN, state=CONNECTING, exception={com.mongodb.MongoSocketOpenException: Exception opening socket}, caused by {java.net.ConnectException: Connection refused: connect}}]
Does anyone have any experience with OpenShift that could give me some advice?
If OpenShift is not an option, could anyone give some suggestion about a free MongoDB cloud service that is not 3.0.X+?
Just would like to remind that this is for college study that’s why we are not investing money on it.
Thanks in advance.

Cassandra-cli cant connect to remote cassandra server

I have a cassandra server running on a server(serv1). cassandra-cli can connect to it when run on serv1. However, when i try to connect to it through some other server(serv2), i get the following exception:
org.apache.thrift.transport.TTransportException: java.net.ConnectException: Connection refused
at org.apache.thrift.transport.TSocket.open(TSocket.java:183)
at org.apache.thrift.transport.TFramedTransport.open(TFramedTransport.java:81)
at org.apache.cassandra.cli.CliMain.connect(CliMain.java:80)
at org.apache.cassandra.cli.CliMain.main(CliMain.java:256)
Caused by: java.net.ConnectException: Connection refused
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:351)
at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:213)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:200)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)
at java.net.Socket.connect(Socket.java:529)
at org.apache.thrift.transport.TSocket.open(TSocket.java:178)
... 3 more
Exception connecting to jckstore/9160. Reason: Connection refused.
I looked in cassandra.yaml and found that the property "listen_address" is configured to "localhost" and using 0.0.0.0 is severely discouraged. I tried to change localhost to serv2, ip address of serv1 but nothing worked. Even commenting out didnt help.
Is there a way i can make my cassandra server listen on all the ip's without using 0.0.0.0

I was able to solve the problem as following:
changing the rpc_address property in cassandra.yaml to 0.0.0.0 instead of localhost.
set the broadcast_rpc_address property in cassandra.yaml to a value other than 0.0.0.0
Then I can access.

Cassandra cli uses thrift to connect to Cassandra. The rpc_address decides how the thrift clients can connect to Cassandra. Setting it to 0.0.0.0 will work, but setting it to the hostname of the server and then using the same hostname to connect will also work.

I also had the same problem, and I was constantly surprised because it was configured correctly. In the end, I found out it was permission issues:
chown -R cassandra: /var/lib/cassandra
chown -R cassandra: /var/log/cassandra
Hope it helps :-)

I had the same problem. I fixed this by updating the snappy temp dir VM option to point to the right directory.
VM_OPTS="$JVM_OPTS -Dorg.xerial.snappy.tempdir=/home/users/local/user/cassandra_home/snap
Hope this helps!

I also had the same problem "Connection refused". Changing the rpc_address from "localhost" to the same hostname as listen_address worked for me.

I also had the same problem "Connection refused". Changing start_rpc: to true fixed it for me.