Develop Reference

Simple SocketHandler for java8 logging(java.util.logging) throws ConnectionException

The intention is to stream the log during runtime on a specific host:port, so that the logs are accessible to users outside the running system, from browser.
As you can see, i have created a simple SocketHandler for java8 logging(java.util.logging), is there something that i have missed?
import java.net.MalformedURLException;
import java.net.URL;
import java.io.IOException;
import java.util.logging.Handler;
import java.util.logging.Level;
import java.util.logging.LogRecord;
import java.util.logging.Logger;
import java.util.logging.SocketHandler;
import java.util.logging.XMLFormatter;
public class Main {
public static void main(String[] args) throws Exception {
Logger logger = Logger.getLogger("concrete.log");
SocketHandler handler = new SocketHandler("HOSTNAME", 19004);
LogRecord logRec = new LogRecord(Level.INFO, "Log recorded");
handler.publish(logRec);
handler.setFormatter(new XMLFormatter());
logger.addHandler(handler);
logger.info("socket handler info message");
}
}
When i run the code, i see the following exception, i have tried checking the system firewall settings on both local(mac/windows) and remote(Linux) and seen that the settings do not block 19004 port
Exception in thread "main" java.net.ConnectException: Connection refused (Connection refused)
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:476)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:218)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:200)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:394)
at java.net.Socket.connect(Socket.java:606)
at java.net.Socket.connect(Socket.java:555)
at java.net.Socket.<init>(Socket.java:451)
at java.net.Socket.<init>(Socket.java:228)
at java.util.logging.SocketHandler.connect(SocketHandler.java:167)
at java.util.logging.SocketHandler.<init>(SocketHandler.java:154)
at Main.main(Main.java:16)
UPDATE
As suggested by bosowski
When i create Socket to listen to a specific port, the log messages are getting printed on the console of the host. However, am unable to access hostname:port for the log to be streamed from the browser. Is there anything specific that needs to be performed after this step?
Please let me know
import java.io.*;
import java.net.*;
public class MyServer {
public static void main(String[] args)
{
try {
ServerSocket ss = new ServerSocket(19004);
Socket soc = ss.accept();
DataInputStream dis
= new DataInputStream(soc.getInputStream());
String str = (String)dis.readUTF();
System.out.println("message= " + str);
ss.close();
}
catch (Exception e) {
System.out.println(e);
}
}
}

SocketHandler does not open up a port to connect to, if that's what you're assuming. It tries to connect to the specified host and port, so you need to have a port that is listening on the host that you are trying to connect to.
https://docs.oracle.com/javase/8/docs/api/java/util/logging/SocketHandler.html#SocketHandler-java.lang.String-int-
<handler-name>.host specifies the target host name to connect to (no default).
<handler-name>.port specifies the target TCP port to use (no default).
If you do indeed have a listening TCP port on the hostname that you're trying to connect to, you can try running sudo nmap -F hostname to check if the port is indeed accessible from your machine.

How to connect to Apache Hive Using SSL certificate from Java JDBC?

I am currently trying to make a simple connection between a Java class and an Apache Hive server.
However, I have not been able to do it due to a javax.net.ssl.SSLPeerUnverifiedException error.
This is the Java code that I am executing:
import java.sql.Connection;
import java.sql.DriverManager;
import java.util.logging.Logger;
public class Main {
public static void main(String[] args) {
Connection con = null;
try {
String conStr = "jdbc:hive2://{{domain}}:{{port}}/default;ssl=true;sslTrustStore=C:/DBVisualization/gateway.jks;trustStorePassword=Password1;transportMode=http;httpPath=/gateway/default/hive";
Class.forName("org.apache.hive.jdbc.HiveDriver");
con = DriverManager.getConnection(conStr, "user", "password");
if(con != null)
System.out.println("Connected");
} catch (Exception ex) {
Logger.getAnonymousLogger().severe("There was an error while connecting to Hive");
}
}
}
And this is the error I am getting:
Could not open client transport with JDBC Uri: jdbc:hive2:{{url}}:{{port}}/default;ssl=true;sslTrustStore=C:/DBVisualization/cacerts;trustStorePassword=changeit;transportMode=http;httpPath=/gateway/default/hive: Could not establish connection to jdbc:hive2://{{url}}:{{port}}/default;ssl=true;sslTrustStore=C:/DBVisualization/cacerts;trustStorePassword=changeit;transportMode=http;httpPath=/gateway/default/hive: javax.net.ssl.SSLPeerUnverifiedException: Certificate for <IP> doesn't match any of the subject alternative names: []
As you can see I am pointing to the file where the certificate is, I used that same certificate for set up a DB visualizer connection and it worked. I am just do not know if for Java a different certificate is required. What am I doing wrong?

How to give certificate to Java Websocket?

Forgive me for the newb question, but I am confused and obviously not understanding the fundamentals or explanations of how to use a Websocket server hosted over HTTPS. Everything I find online leads me to have more questions than answers.
I have a Websocket server hosted on my HTTPS website using Java code.
This is my WebsocketServer.java file:
import org.java_websocket.WebSocket;
import org.java_websocket.handshake.ClientHandshake;
import org.java_websocket.server.WebSocketServer;
import java.net.InetSocketAddress;
import java.util.HashSet;
import java.util.Set;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
public class WebsocketServer extends WebSocketServer {
private static final Logger logger = LogManager.getLogger(WebsocketServer.class);
private static int TCP_PORT = 6868;
private static Set<WebSocket> conns;
public WebsocketServer() {
super(new InetSocketAddress(TCP_PORT));
conns = new HashSet<>();
}
#Override
public void onOpen(WebSocket conn, ClientHandshake handshake) {
conns.add(conn);
logger.info("New connection from " + conn.getRemoteSocketAddress().getAddress().getHostAddress());
logger.info("Size of connection list: " + conns.size());
}
#Override
public void onClose(WebSocket conn, int code, String reason, boolean remote) {
conns.remove(conn);
logger.info("Closed connection to " + conn.getRemoteSocketAddress().getAddress().getHostAddress());
}
#Override
public void onMessage(WebSocket conn, String message) {
logger.info("Message from client: {}", message);
// for (WebSocket sock : conns) {
// sock.send("SENDING BACK" + message);
// }
}
#Override
public void onError(WebSocket conn, Exception ex) {
// ex.printStackTrace();
try {
if (conn != null) {
conns.remove(conn);
// do some thing if required
}
logger.info("ERROR from {}", conn.getRemoteSocketAddress().getAddress().getHostAddress());
} catch (Exception e) {
logger.info("onError: WebSocketServer may already be running");
}
}
public Set<WebSocket> getConns() {
return conns;
}
}
Then I started the WebsocketServer like this:
WebsocketServer websocketServer;
// Start socket server
websocketServer = new WebsocketServer();
websocketServer.start();
And on the client side, I connect to it like this:
// APP_WEB_SOCKET is the url to my site: api.my_custom_domain.com
var connection = new WebSocket("wss://" + APP_WEB_SOCKET + ":6868");
QUESTIONS:
I keep reading that I need a certificate if I want to use wss over HTTPS, but cannot find any documents that explain what this means in a way that I can understand.
My app is hosted in AWS Elastic Beanstalk environment. Do I need to somehow add a certificate to the setup of the WebsocketServer in my Java code?
Example:
WebsocketServer websocketServer;
// Start socket server
websocketServer = new WebsocketServer();
// example guessing
websocketServer.cert = "SOMETHING";??
websocketServer.start();
Does the client code need to be changed at all?
Who needs the certificate?
If someone could please explain what I am missing or point me in the correct direction, I would really appreciate it.

Keep it easy.
Certs inside your application are complex - they are hard to manage and you will get problems to run your application in a modern cloud environment (start new environments, renew certs, scale your application, ...).
Simple conclusion: Dont implement any certs.
How-to get encrypted connections?
As Mike already pointed out in the comments: WebSockets are just upgraded HTTP(S) connections. A normal webserver (nginx, apache) takes care about the certs. It can be done in kubernetes (as ingress-controller) or with a "bare-metal" webserver.
Both of them should act as a reverse-proxy. This means: Your java-application doesn't know anything about certs. It has just unencrypted connections - like in your code on port 6868.
But the client will not use this port. 6868 is only internally reachable.
The client will call your reverse-proxy at the normal HTTPS port (=443). The reverse-proxy will forward the connection to your java-application.
Here some links for further information:
nginx reverse-proxy
nginx reverse-proxy for websocket
tutorial for java behind reverse-proxy
LetsEncrypt for automatic and free certs

Connect to RServe from JAVA using authentication

I am running RServe from Server machine using cmd
Rserve.exe --RS-conf Rserv.conf --RS-port 12306
Rserv.conf file has following content:
pwdfile RserveAuth.txt
auth required
remote enable
plaintext disable
RserveAuth.txt has following contents:
Admin 123456
I am connecting to R Server from JAVA
import org.rosuda.REngine.REXPMismatchException;
import org.rosuda.REngine.REngineException;
import org.rosuda.REngine.Rserve.RConnection;
import org.rosuda.REngine.Rserve.RserveException;
import org.rosuda.REngine.REXP;
import org.rosuda.REngine.*;
public class ConnecttoR
{
...
...
public void connectR()
{
try
{
RConnection connection = new RConnection("172.16.33.242",12306); // Works if authentication is not required in Rserv.conf
}
catch (RserveException e) {
e.printStackTrace();
}
catch(REXPMismatchException e){
e.printStackTrace();
}
catch(REngineException e){
e.printStackTrace();
}
}
}
Connection to Rserve is open to all without username & Password. How shall I add security and allow connection only with valid credentials to access Rserve

As you have enabled the authentification after creating the connection as a first command you need to execute the login command. The Java library has a special wrapper for it.
See code below for example use case.
RConnection connection = new RConnection("127.0.0.1",12306);
connection.login("Admin", "123456");
REXP x = connection.eval("R.version.string");
System.out.println(x.asString());
Also, I would recommend using full path as the pwdfile value.

WebSphere admin client connection error

I am getting connection error on WebSphere admin client creation process.
I read many forums but cannot fix it.
"Exception creating Admin Client Connection: com.ibm.websphere.management.exception.ConnectorException: ADMC0016E: The system cannot create a SOAP connector to connect to host "111.xxxx.." at port 8879."
My dmgr port is 8879
Host name is "111.xxxx.."
Servers config files located c:\temp\soap.client.props, DummyClientTrustFile.jks, DummyClientKeyFile.jks
My code is below:
import java.util.Date;
import java.util.Properties;
import java.util.Set;
import javax.management.InstanceNotFoundException;
import javax.management.MalformedObjectNameException;
import javax.management.Notification;
import javax.management.NotificationListener;
import javax.management.ObjectName;
import com.ibm.websphere.management.AdminClient;
import com.ibm.websphere.management.AdminClientFactory;
import com.ibm.websphere.management.exception.ConnectorException;
public class AdminClientConnection
{
private AdminClient adminClient;
public static void main(String[] args)
{
AdminClientConnection aClient = new AdminClientConnection();
// Create an AdminClient
aClient.createAdminClient();
}
private void createAdminClient()
{
// Set up a Properties object for the JMX connector attributes
Properties clientProps = new Properties();
clientProps.setProperty(
AdminClient.CONNECTOR_TYPE, AdminClient.CONNECTOR_TYPE_SOAP);
clientProps.setProperty(AdminClient.CONNECTOR_HOST, "111.xxxx..");
clientProps.setProperty(AdminClient.CONNECTOR_PORT, "8879");
clientProps.setProperty(AdminClient.CONNECTOR_SECURITY_ENABLED, "true");
clientProps.setProperty(AdminClient.USERNAME, "usr");
clientProps.setProperty(AdminClient.PASSWORD, "pass");
clientProps.setProperty(AdminClient.CONNECTOR_SOAP_CONFIG, "c:/temp/soap.client.props");
clientProps.setProperty("javax.net.ssl.trustStore", "c:/temp/DummyClientTrustFile.jks");
clientProps.setProperty("javax.net.ssl.keyStore", "c:/temp/DummyClientKeyFile.jks");
clientProps.setProperty("javax.net.ssl.trustStorePassword", "WebAS");
clientProps.setProperty("javax.net.ssl.keyStorePassword", "WebAS");
// Get an AdminClient based on the connector properties
try
{
adminClient = AdminClientFactory.createAdminClient(clientProps);
}
catch (ConnectorException e)
{
System.out.println("Exception creating Admin Client Connection: " + e);
System.exit(-1);
}
System.out.println("Connected to Application Server");
}
}

Be sure that CONNECTOR_PORT is true, CONNECTOR_SECURITY_ENABLED is not neccassary. Be sure that soap.client.props and jks files are gathered from the connector host.