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Connectivity issues Oracle cloud

I have an issue with my applications using oracle RDBMS version 12.1.0.2.0.
Although I am connecting to the database correctly, sometimes I get (A) some spurious disconnections with the exception
java.sql.SQLRecoverableException: IO Error: Connection reset
at java.lang.Thread.run(Unknown Source)
Suppressed: java.sql.SQLRecoverableException: Closed Connection
...
Caused by: java.net.SocketException: Connection reset
at java.net.SocketInputStream.read(Unknown Source)
at java.net.SocketInputStream.read(Unknown Source)
at oracle.net.ns.Packet.receive(Packet.java:311)
at oracle.net.ns.DataPacket.receive(DataPacket.java:105)
and (B) some other times I can't even create a connection
java.sql.SQLRecoverableException: IO Error: Software caused connection abort: recv failed
...
Caused by: java.net.SocketException: Software caused connection abort: recv failed
Or
Caused by: java.sql.SQLRecoverableException: IO Error: The Network Adapter could not establish the connection
at oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:673)
at oracle.jdbc.driver.PhysicalConnection.<init>(PhysicalConnection.java:715)
at oracle.jdbc.driver.T4CConnection.<init>(T4CConnection.java:385)
at oracle.jdbc.driver.T4CDriverExtension.getConnection(T4CDriverExtension.java:30)
at oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:564)
at org.jboss.jca.adapters.jdbc.local.LocalManagedConnectionFactory.createLocalManagedConnection(LocalManagedConnectionFactory.java:322)
... 6 more
Caused by: oracle.net.ns.NetException: The Network Adapter could not establish the connection
at oracle.net.nt.ConnStrategy.execute(ConnStrategy.java:445)
at oracle.net.resolver.AddrResolution.resolveAndExecute(AddrResolution.java:464)
at oracle.net.ns.NSProtocol.establishConnection(NSProtocol.java:594)
at oracle.net.ns.NSProtocol.connect(NSProtocol.java:229)
at oracle.jdbc.driver.T4CConnection.connect(T4CConnection.java:1360)
at oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:486)
... 11 more
Caused by: java.net.ConnectException: Connection refused: connect
at java.net.TwoStacksPlainSocketImpl.socketConnect(Native Method) [rt.jar:1.8.0_92]
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350) [rt.jar:1.8.0_92]
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206) [rt.jar:1.8.0_92]
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188) [rt.jar:1.8.0_92]
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172) [rt.jar:1.8.0_92]
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) [rt.jar:1.8.0_92]
at java.net.Socket.connect(Socket.java:589) [rt.jar:1.8.0_92]
at oracle.net.nt.TcpNTAdapter.connect(TcpNTAdapter.java:162)
at oracle.net.nt.ConnOption.connect(ConnOption.java:133)
at oracle.net.nt.ConnStrategy.execute(ConnStrategy.java:411)
Some of the applications are using wildfly v8.2 with the following standalone settings
<connection-url>connectionString</connection-url>
<driver-class>oracle.jdbc.OracleDriver</driver-class>
<driver>ojdbc7.jar</driver>
<pool>
<min-pool-size>12</min-pool-size>
<max-pool-size>24</max-pool-size>
<prefill>false</prefill>
<use-strict-min>true</use-strict-min>
</pool>
<security>
<user-name>user</user-name>
<password>password</password>
</security>
<validation>
<valid-connection-checker class-name="org.jboss.jca.adapters.jdbc.extensions.oracle.OracleValidConnectionChecker"/>
<validate-on-match>false</validate-on-match>
<background-validation>true</background-validation>
<background-validation-millis>300000</background-validation-millis>
<exception-sorter class-name="org.jboss.jca.adapters.jdbc.extensions.oracle.OracleExceptionSorter"/>
</validation>
<timeout>
<set-tx-query-timeout>false</set-tx-query-timeout>
<blocking-timeout-millis>0</blocking-timeout-millis>
<idle-timeout-minutes>8</idle-timeout-minutes>
<query-timeout>0</query-timeout>
<use-try-lock>0</use-try-lock>
<allocation-retry>0</allocation-retry>
<allocation-retry-wait-millis>0</allocation-retry-wait-millis>
</timeout>
<statement>
<track-statements>true</track-statements>
<share-prepared-statements>false</share-prepared-statements>
</statement>
And the rest are standalone applications using JDBC.
I already checked the listener logs and according to them, the application never sent a request (B scenario).
Please note that the application retries one second later and successfully connects and that the applications are deployed within the same network.
Can you please help identifying the cause of it ?
Thank you.

(A): The error indicates that the socket has been gracefully closed. This could be a micro network outage or it could be a firewall somewhere in the middle between the app and the Database that closes a socket when it detects no activity for more than x seconds. It may help to turn on keep alive by setting the oracle.net.keepAlive connection property to true. Note that this property can also be set as a Java system property using -D.
(B): The listener may refuse socket connection attempts if a rate limit has been configured which helps during logon storms. A proper client should retry with some delay. The JDBC thin driver in 12.1.0.2 supports these two parameters in the URL (values are in seconds). For example:
(DESCRIPTION_LIST=
(DESCRIPTION=
(CONNECT_TIMEOUT=10)(RETRY_COUNT=3)(RETRY_DELAY=3)
(ADDRESS_LIST=
(ADDRESS=(PROTOCOL=tcp)(HOST=myhost1)(PORT=1521))
(ADDRESS=(PROTOCOL=tcp)(HOST=myhost2)(PORT=1521)))
(CONNECT_DATA=(SERVICE_NAME=example1.com)))
(DESCRIPTION=
(CONNECT_TIMEOUT=60)(RETRY_COUNT=1)(RETRY_DELAY=5)
(ADDRESS_LIST=
(ADDRESS=(PROTOCOL=tcp)(HOST=myhost3)(PORT=1521))
(ADDRESS=(PROTOCOL=tcp)(HOST=myhost4)(PORT=1521)))
(CONNECT_DATA=(SERVICE_NAME=example2.com))))
The doc is here.

Java RMI starting server throws exception [duplicate]

This question already has an answer here:
RMI connection refused on localhost
(1 answer)
Closed 5 years ago.
I receive an error trying to start an RMI server and I can't figure out why. And another question: How do I set up the IP address of the server.
Here is the stack trace:
java.rmi.ConnectException: Connection refused to host: 127.0.1.1; nested exception is:
java.net.ConnectException: Connection refused
java.rmi.ConnectException: Connection refused to host: 127.0.1.1; nested exception is:
java.net.ConnectException: Connection refused
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:342)
at sun.rmi.registry.RegistryImpl_Stub.bind(Unknown Source)
at Main.main(Main.java:22)
Caused by: java.net.ConnectException: Connection refused
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:345)
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 java.net.Socket.connect(Socket.java:538)
at java.net.Socket.<init>(Socket.java:434)
at java.net.Socket.<init>(Socket.java:211)
at sun.rmi.transport.proxy.RMIDirectSocketFactory.createSocket(RMIDirectSocketFactory.java:40)
at sun.rmi.transport.proxy.RMIMasterSocketFactory.createSocket(RMIMasterSocketFactory.java:148)
at sun.rmi.transport.tcp.TCPEndpoint.newSocket(TCPEndpoint.java:613)
... 5 more
Thank you!

You haven't started the RMI Registry.

Why I cannot send email via Log4j SMTPAppender?

I use Log4j 1.2.17 for loggining. I want to send error message to my email but I have some problems.
Here is my properies file:
log4j.appender.email=org.apache.log4j.net.SMTPAppender
log4j.appender.email.Threshold=WARN
log4j.appender.email.SMTPHost=smtp.gmail.com
log4j.appender.email.SMTPUsername=myGmailAddress
log4j.appender.email.SMTPPassword=passwordToMyGmailAddress
log4j.appender.email.From=myGmailAddress
log4j.appender.email.To=anotherGmailAddress
log4j.appender.email.Subject=Log of messages
log4j.appender.email.layout=org.apache.log4j.SimpleLayout
Where myGmailAddress and passwordToMyGmailAddress are my valid gmail and password. anotherGmailAddress - another valid gmail
When I run my app I get this:
log4j:ERROR Error occured while sending e-mail notification.
javax.mail.MessagingException: Could not connect to SMTP host: smtp.gmail.com, port: 25;
nested exception is:
java.net.ConnectException: Connection timed out: connect
at com.sun.mail.smtp.SMTPTransport.openServer(SMTPTransport.java:1282)
at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:370)
at javax.mail.Service.connect(Service.java:297)
at javax.mail.Service.connect(Service.java:156)
at javax.mail.Service.connect(Service.java:105)
at javax.mail.Transport.send0(Transport.java:168)
at javax.mail.Transport.send(Transport.java:98)
at org.apache.log4j.net.SMTPAppender.sendBuffer(SMTPAppender.java:416)
at org.apache.log4j.net.SMTPAppender.append(SMTPAppender.java:256)
at org.apache.log4j.AppenderSkeleton.doAppend(AppenderSkeleton.java:251)
at org.apache.log4j.helpers.AppenderAttachableImpl.appendLoopOnAppenders(AppenderAttachableImpl.java:66)
at org.apache.log4j.Category.callAppenders(Category.java:206)
at org.apache.log4j.Category.forcedLog(Category.java:391)
at org.apache.log4j.Category.error(Category.java:305)
at epam.lab.log4j.utils.Printer.printMessage(Printer.java:13)
at epam.lab.log4j.Launcher.main(Launcher.java:35)
Caused by: java.net.ConnectException: Connection timed out: connect
at java.net.DualStackPlainSocketImpl.connect0(Native Method)
at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:79)
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 java.net.Socket.connect(Socket.java:538)
at com.sun.mail.util.SocketFetcher.createSocket(SocketFetcher.java:232)
at com.sun.mail.util.SocketFetcher.getSocket(SocketFetcher.java:189)
at com.sun.mail.smtp.SMTPTransport.openServer(SMTPTransport.java:1250)
... 15 more
I spent several hours when tried to solve this, but I do not found solution.
I tried to change port, disable Antivirus&Firewall, use custom SMTPAppender etc...But it did not help...
Any ideas how to solve this?

org.apache.axis2.AxisFault connection refused

I'm getting the following error while tryng to suscribe to a service from client app.
Can somebody tell me the reason for this exception?
Thanks in advance
org.apache.axis2.AxisFault: Conexión rehusada
at org.apache.axis2.AxisFault.makeFault(AxisFault.java:430)
at org.apache.axis2.transport.http.HTTPSender.sendViaPost(HTTPSender.java:197)
at org.apache.axis2.transport.http.HTTPSender.send(HTTPSender.java:75)
at org.apache.axis2.transport.http.CommonsHTTPTransportSender.writeMessageWithCommons(CommonsHTTPTransportSender.java:404)
at org.apache.axis2.transport.http.CommonsHTTPTransportSender.invoke(CommonsHTTPTransportSender.java:231)
at org.apache.axis2.engine.AxisEngine.send(AxisEngine.java:443)
at org.apache.axis2.description.OutInAxisOperationClient.send(OutInAxisOperation.java:406)
at org.apache.axis2.description.OutInAxisOperationClient.executeImpl(OutInAxisOperation.java:229)
at org.apache.axis2.client.OperationClient.execute(OperationClient.java:165)
at com.tissat.echo.wsdl.EchoServiceStub.suscribe(EchoServiceStub.java:772)
at com.tissat.echo.servicios.ServicioLisa.cliSuscribirse(ServicioLisa.java:122)
at com.tissat.echo.servicios.ClienteLisa.Conectar(ClienteLisa.java:23)
at com.tissat.echo.rmi.ServidorLisaTomcat.connectSuscription(ServidorLisaTomcat.java:150)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:322)
at sun.rmi.transport.Transport$1.run(Transport.java:177)
at sun.rmi.transport.Transport$1.run(Transport.java:174)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Transport.java:173)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:556)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:811)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:670)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.net.ConnectException: Conexión rehusada
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:392)
at java.net.Socket.connect(Socket.java:579)
at sun.security.ssl.SSLSocketImpl.connect(SSLSocketImpl.java:618)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.commons.httpclient.protocol.ReflectionSocketFactory.createSocket(ReflectionSocketFactory.java:140)
at org.apache.commons.httpclient.protocol.SSLProtocolSocketFactory.createSocket(SSLProtocolSocketFactory.java:130)
at org.apache.commons.httpclient.HttpConnection.open(HttpConnection.java:707)
at org.apache.commons.httpclient.MultiThreadedHttpConnectionManager$HttpConnectionAdapter.open(MultiThreadedHttpConnectionManager.java:1361)
at org.apache.commons.httpclient.HttpMethodDirector.executeWithRetry(HttpMethodDirector.java:387)
at org.apache.commons.httpclient.HttpMethodDirector.executeMethod(HttpMethodDirector.java:171)
at org.apache.commons.httpclient.HttpClient.executeMethod(HttpClient.java:397)
at org.apache.axis2.transport.http.AbstractHTTPSender.executeMethod(AbstractHTTPSender.java:621)
at org.apache.axis2.transport.http.HTTPSender.sendViaPost(HTTPSender.java:193)
... 26 more
org.apache.axis2.AxisFault: Conexión rehusada

Connection refused means the following:
The host exists, nothing is listening for connections on that port.
Alternatively, a firewall is blocking that port.
More at: http://axis.apache.org/axis/java/client-side-axis.html

We faced similar issue and we were getting Read Time Out while trying to invoke a secured webservice, after a long analysis we found out that there was a mismatch in the transport protocol version. Web-service was servicing on http1.0 and we were invoking it using http1.1. We modified the protocol version in our client code which resolves this issue:
Below is the code to specify http version-1.0
options.setProperty(org.apache.axis2.transport.http.HTTPConstants.HTTP_PROTOCOL_VERSION, org.apache.axis2.transport.http.HTTPConstants.HEADER_PROTOCOL_10);

It seems that the Service is not running where you think it is running. Check whether it is running properly in the desired port. That's why ConnectionRefused Exception is thrown. Make sure you don't have firewall blocking the port.
if service on that machine has NOT created a socket and is NOT listening on that port.you will see the message connection refused.

Send mail using rnote domino in Java

I'm working on some application which should send mail sometimes. Unfortunately administrator said that I can't send mail over traditional smtp protocol because he blocks it.
He told me that there is 2 ways to do it:
1) "set relay server to application in this case somestringrnotesmtp.domain.com"
In this case it looks like some smtp server provided by Lotus rnotes. But when I try to send mail using org.apache.commons.mail I'm getting exception
Caused by: javax.mail.MessagingException: Could not connect to SMTP host: somestringrnotesmtp.domain.com, port: 465;
nested exception is:
java.net.ConnectException: Connection refused
at com.sun.mail.smtp.SMTPTransport.openServer(SMTPTransport.java:1972)
at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:642)
at javax.mail.Service.connect(Service.java:295)
at javax.mail.Service.connect(Service.java:176)
at javax.mail.Service.connect(Service.java:125)
at javax.mail.Transport.send0(Transport.java:194)
at javax.mail.Transport.send(Transport.java:124)
at org.apache.commons.mail.Email.sendMimeMessage(Email.java:1388)
... 40 more
Caused by: java.net.ConnectException: Connection refused
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.AbstractPlainSocketImpl.doConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.connectToAddress(Unknown Source)
at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
at java.net.SocksSocketImpl.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at sun.security.ssl.SSLSocketImpl.connect(Unknown Source)
at com.sun.mail.util.SocketFetcher.createSocket(SocketFetcher.java:317)
at com.sun.mail.util.SocketFetcher.getSocket(SocketFetcher.java:207)
at com.sun.mail.smtp.SMTPTransport.openServer(SMTPTransport.java:1938)
... 47 more
"use unix sendmail for this purpose"
I have no idea how to do it this way. Is there any java library which does that?