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UnknownHostException: while connecting to database server

I am trying to host MySQL database on 1nd1.com. I have created a database with few tables. Getting below error while connecting to 1and1 database from java application.
When pinging from the command prompt using "ping hostname" command, getting a failure in response.
Is there any way to connect to this host from java program?
com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception:
** BEGIN NESTED EXCEPTION **
java.net.UnknownHostException
MESSAGE: db726853948.db.1and1.com
STACKTRACE:
java.net.UnknownHostException: db726853948.db.1and1.com
at java.net.Inet6AddressImpl.lookupAllHostAddr(Native Method)
at java.net.InetAddress$2.lookupAllHostAddr(InetAddress.java:907)
at java.net.InetAddress.getAddressesFromNameService(InetAddress.java:1302)
at java.net.InetAddress.getAllByName0(InetAddress.java:1255)
at java.net.InetAddress.getAllByName(InetAddress.java:1171)
at java.net.InetAddress.getAllByName(InetAddress.java:1105)
at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:246)
at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:271)
at com.mysql.jdbc.Connection.createNewIO(Connection.java:2771)
at com.mysql.jdbc.Connection.<init>(Connection.java:1555)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285)
at java.sql.DriverManager.getConnection(DriverManager.java:664)
at java.sql.DriverManager.getConnection(DriverManager.java:247)
at Contct.insertDetails(Contct.java:11)
at Contct.main(Contct.java:28)
** END NESTED EXCEPTION **
Last packet sent to the server was 0 ms ago.

try adding your hostname to your host file
for example:
your_host_ip(122.2.2.1) hostname(db726853948.db.1and1.com)

Could not open JPA EntityManager for transaction; nested exception is javax.persistence.PersistenceException

when i run my code, i get this exception:
com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: 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:422)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1121)
at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:357)
at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2482)
at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2519)
at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2304)
at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:834)
at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)
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:422)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:416)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:346)
at java.sql.DriverManager.getConnection(DriverManager.java:664)
at java.sql.DriverManager.getConnection(DriverManager.java:208)
at org.springframework.jdbc.datasource.DriverManagerDataSource.getConnectionFromDriverManager(DriverManagerDataSource.java:153)
at org.springframework.jdbc.datasource.DriverManagerDataSource.getConnectionFromDriver(DriverManagerDataSource.java:144)
at org.springframework.jdbc.datasource.AbstractDriverBasedDataSource.getConnectionFromDriver(AbstractDriverBasedDataSource.java:155)
at org.springframework.jdbc.datasource.AbstractDriverBasedDataSource.getConnection(AbstractDriverBasedDataSource.java:120)
at org.hibernate.engine.jdbc.connections.internal.DatasourceConnectionProviderImpl.getConnection(DatasourceConnectionProviderImpl.java:139)
at org.hibernate.tool.hbm2ddl.SuppliedConnectionProviderConnectionHelper.prepare(SuppliedConnectionProviderConnectionHelper.java:51)
at org.hibernate.tool.hbm2ddl.DatabaseExporter.<init>(DatabaseExporter.java:52)
at org.hibernate.tool.hbm2ddl.SchemaExport.execute(SchemaExport.java:367)
at org.hibernate.tool.hbm2ddl.SchemaExport.create(SchemaExport.java:304)
at org.hibernate.tool.hbm2ddl.SchemaExport.create(SchemaExport.java:293)
at org.hibernate.internal.SessionFactoryImpl.<init>(SessionFactoryImpl.java:517)
at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1857)
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
Aug 25, 2015 8:23:45 PM com.sun.jersey.spi.container.ContainerResponse mapMappableContainerException
SCHWERWIEGEND: The RuntimeException could not be mapped to a response, re-throwing to the HTTP container
org.springframework.transaction.CannotCreateTransactionException: Could not open JPA EntityManager for transaction; nested exception is javax.persistence.PersistenceException: org.hibernate.exception.JDBCConnectionException: Could not open connection
at org.springframework.orm.jpa.JpaTransactionManager.doBegin(JpaTransactionManager.java:431)
at org.springframework.transaction.support.AbstractPlatformTransactionManager.getTransaction(AbstractPlatformTransactionManager.java:373)
at org.springframework.transaction.interceptor.TransactionAspectSupport.createTransactionIfNecessary(TransactionAspectSupport.java:457)
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:276)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:207)
at com.sun.proxy.$Proxy76.create(Unknown Source)
I don't know where is the problem. But yesterday i worked fine.
my database.properties:
jdbc.driverClassName=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/streaming
jdbc.username=root
jdbc.password=password
hibernate.dialect=org.hibernate.dialect.MySQLDialect
hibernate.showsql=true
hibernate.hbm2ddl.auto=create
It is possible for me to run mysql directly from command line. Where is the problem? Was is wrong.
I use spring 4 and hibernate with mysql as database language.
Has someone any ideas?
Thank.

There is CommunicationsException: Communications link failure.
If you get a SQLException: Connection refused or Connection timed out or a MySQL specific
CommunicationsException: Communications link failure
then it means that the DB isn't reachable at all. This can have one or more of the following causes:
IP address or hostname in JDBC URL is wrong.
Hostname in JDBC URL is not recognized by local DNS server.
Port number is missing or wrong in JDBC URL.
DB server is down.
DB server doesn't accept TCP/IP connections.
DB server has run out of connections.
Something in between Java and DB is blocking connections, e.g. a firewall or proxy.
To solve the one or the other, follow the following advices:
Verify and test them with ping.
Refresh DNS or use IP address in JDBC URL instead.
Verify it based on my.cnf of MySQL DB.
Start the DB.
Verify if mysqld is started without the --skip-networking option.
Restart the DB and fix your code accordingly that it closes connections in finally.
Disable firewall and/or configure firewall/proxy to allow/forward the port.
Source: More Details

I see that #Amit Tamrakar have good answer but I want to add:
if you make a lot of requests to db, (I mean connections), may be that application (some app thread) just wait for use free connection from app db connection pool, but throws timeout exception.
.h.engine.jdbc.spi.SqlExceptionHelper : HikariPool-1 - Connection is not available, request timed out after 30005ms.
Could not open JPA EntityManager for transaction; nested exception is org.hibernate.exception.JDBCConnectionException: Unable to acquire JDBC Connection
You can try to increase db connection pool in application config file, for example:
spring.datasource.hikari.maximum-pool-size=20
You can set size which you need. This config in app by default is 8.
And we need remember that each db have own free db connection size which we don't need exceed.
I mean if db have 5 free connection and you want to use 10 connections in your app then we will receive so exceptions.

DB is down.
You must start the DB server and check connectivity with either telnet or mysql command line client first.

I was not unable to figure out the exact cause, but I realized that it was because of some thread pools since I was able to connect to the db using the terminal.
for checking the connectivity you can use the below command.
psql -h hostname -U username -d database
so restarting the server worked for me.

Exception while connecting to mysql in 000webhost [duplicate]

This question already has answers here:
Java mySQL with 000webhost
(4 answers)
Closed 9 years ago.
I have created a database on 000webhost.com and now I am trying to connect to the database through java as:
Class.forName("com.mysql.jdbc.Driver");
Connection conn = DriverManager.getConnection("jdbc:mysql://mysql14.000webhost.com/a2509514_Email", username, pass);
But when I execute it I am getting the following exception:
com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception:
** BEGIN NESTED EXCEPTION **
java.net.ConnectException
MESSAGE: Connection timed out: connect
STACKTRACE:
java.net.ConnectException: Connection timed out: connect
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)
at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)
at java.net.Socket.connect(Socket.java:525)
at java.net.Socket.connect(Socket.java:475)
at java.net.Socket.<init>(Socket.java:372)
at java.net.Socket.<init>(Socket.java:215)
at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:256)
at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:271)
at com.mysql.jdbc.Connection.createNewIO(Connection.java:2771)
at com.mysql.jdbc.Connection.<init>(Connection.java:1555)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285)
at java.sql.DriverManager.getConnection(DriverManager.java:582)
at java.sql.DriverManager.getConnection(DriverManager.java:185)
at trapack.Experiment.sample(Experiment.java:20)
at trapack.Experiment.main(Experiment.java:35)
** END NESTED EXCEPTION **
Last packet sent to the server was 0 ms ago.
at com.mysql.jdbc.Connection.createNewIO(Connection.java:2847)
at com.mysql.jdbc.Connection.<init>(Connection.java:1555)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285)
at java.sql.DriverManager.getConnection(DriverManager.java:582)
at java.sql.DriverManager.getConnection(DriverManager.java:185)
at trapack.Experiment.sample(Experiment.java:20)
at trapack.Experiment.main(Experiment.java:35)
There is no direct discussion about this specific topic so any help would be really appreciated.

I got a similar problem when I was using MySQL in AWS (Amazon Web Services - Cloud Computing)
I had to give permission to my computer IP in the site (AWS).
I recommend you to use http://www.heidisql.com/ to test if you can connect to your database in 000webhost. If you succed, the error is in your Java code, if you fail to connect it can be your credentials, security configuration of your host site or just a horrible connection link you have there.
Give us more information about your problem so we can help you.

Use the connection string provided by 000webhost when you create the user.
000webhost.com creates their own string or host name for creating connection..
Hope it will works.
Thanks

The answer is you must upgrade your account.
The free MySQL from 000webhost doesn't allow you to connect from external applications, just from within pages hosted in their domain.
Please check: How can I connect to MySQL from my computer?

java.rmi.ConnectException: Connection refused to host:

java.rmi.ConnectException: Connection refused to host: IPSERVER0.0.0.0.0; nested exception is:
java.net.ConnectException: Connection timed out
at sun.rmi.transport.tcp.TCPEndpoint.newSocket(TCPEndpoint.java:619)
at sun.rmi.transport.tcp.TCPChannel.createConnection(TCPChannel.java:216)
at sun.rmi.transport.tcp.TCPChannel.newConnection(TCPChannel.java:202)
at sun.rmi.server.UnicastRef.newCall(UnicastRef.java:340)
at sun.rmi.registry.RegistryImpl_Stub.lookup(Unknown Source)
at java.rmi.Naming.lookup(Naming.java:101)
at StartRMI.go(StartRMI.java:14)
at StartRMI.main(StartRMI.java:6)
Caused by: java.net.ConnectException: Connection timed out
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:339)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:200)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:182)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:391)
at java.net.Socket.connect(Socket.java:579)
at java.net.Socket.connect(Socket.java:528)
at java.net.Socket.<init>(Socket.java:425)
at java.net.Socket.<init>(Socket.java:208)
at sun.rmi.transport.proxy.RMIDirectSocketFactory.createSocket(RMIDirectSocketFactory.java:40)
at sun.rmi.transport.proxy.RMIMasterSocketFactory.createSocket(RMIMasterSocketFactory.java:146)
at sun.rmi.transport.tcp.TCPEndpoint.newSocket(TCPEndpoint.java:613)
... 7 more
I get this exception when I try to connect a remote client to my server. My Server is running RMI Server fine, and there no firewall installed. How to fix that issue ?

Check all you network adapters ,some time a VM network adapter interferes in this way .
Which is you current localhost or 127.0.0.1 is not any more referring to you host name or current machine ,which then create a connection refused problem. My General Recommendation is:
1.To check or disable unwanted VM or Network Adapters
2.Ping 127.0.0.1
3.Disable Firewall and Test if all the above doesn't work
4.Add security Manager with a policy file on you server if you haven't done that.

You have not mentioned which OS you are using, if everything is correct in terms of code and firewall then you may need to check the host entries or ip table rules.

Is IPSERVER mapped in /etc/hosts file to the IP address you want?
Check what you get when you do a hostname -i or hostname.
Try putting your IP address instead of the domain name.

Try to start the RMI registry using
start rmiregistry
for default port or
rmiregistry <port_no>
for a specified port.

Java Socket exception while trying to reach .NET WCF web service on IIS

When I call, the service's method, I have Web Service Exception happening which I couldn't figure out for now.
The issue is this, I am running NetBeans 6.8 against IIS 7.0 with the Web Service written using WCF:
javax.xml.ws.WebServiceException: java.net.SocketException: Connection reset
at com.sun.xml.internal.ws.transport.http.client.HttpClientTransport.readResponseCodeAndMessage(HttpClientTransport.java:201)
at com.sun.xml.internal.ws.transport.http.client.HttpTransportPipe.process(HttpTransportPipe.java:151)
at com.sun.xml.internal.ws.transport.http.client.HttpTransportPipe.processRequest(HttpTransportPipe.java:83)
at com.sun.xml.internal.ws.transport.DeferredTransportPipe.processRequest(DeferredTransportPipe.java:105)
at com.sun.xml.internal.ws.api.pipe.Fiber.__doRun(Fiber.java:587)
at com.sun.xml.internal.ws.api.pipe.Fiber._doRun(Fiber.java:546)
at com.sun.xml.internal.ws.api.pipe.Fiber.doRun(Fiber.java:531)
at com.sun.xml.internal.ws.api.pipe.Fiber.runSync(Fiber.java:428)
at com.sun.xml.internal.ws.client.Stub.process(Stub.java:211)
at com.sun.xml.internal.ws.client.sei.SEIStub.doProcess(SEIStub.java:124)
at com.sun.xml.internal.ws.client.sei.SyncMethodHandler.invoke(SyncMethodHandler.java:98)
at com.sun.xml.internal.ws.client.sei.SyncMethodHandler.invoke(SyncMethodHandler.java:78)
at com.sun.xml.internal.ws.client.sei.SEIStub.invoke(SEIStub.java:107)
at $Proxy30.getTwo(Unknown Source)
at HighBeamWcfClient.Main.main(Main.java:28)
Caused by: java.net.SocketException: Connection reset
at java.net.SocketInputStream.read(SocketInputStream.java:168)
at java.io.BufferedInputStream.fill(BufferedInputStream.java:218)
at java.io.BufferedInputStream.read1(BufferedInputStream.java:258)
at java.io.BufferedInputStream.read(BufferedInputStream.java:317)
at sun.net.www.http.HttpClient.parseHTTPHeader(HttpClient.java:687)
at sun.net.www.http.HttpClient.parseHTTP(HttpClient.java:632)
at sun.net.www.http.HttpClient.parseHTTP(HttpClient.java:652)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1072)
at java.net.HttpURLConnection.getResponseCode(HttpURLConnection.java:373)
at com.sun.xml.internal.ws.transport.http.client.HttpClientTransport.readResponseCodeAndMessage(HttpClientTransport.java:198)
How to fix it?

"Connection reset" typically means that someone/something between you and the server is resetting the connection or somehow blocking it. Check that you can connect to the server on the port correctly without any issue, and that there are no firewalls in the way.
A very simple test that you can connect to the port in question is to simply telnet to it with telnet serverhostname portnum, for example telnet stackoverflow.com 80.