I am trying to run the program below, but I am getting this error:
Exception in thread "main" java.net.ConnectException: Connection refused: connect
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 com.rabbitmq.client.ConnectionFactory.createFrameHandler(ConnectionFactory.java:445)
at com.rabbitmq.client.ConnectionFactory.newConnection(ConnectionFactory.java:504)
at com.rabbitmq.client.ConnectionFactory.newConnection(ConnectionFactory.java:533)
at Recieve.main(Recieve.java:14)
The program I am trying to run is:
import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.ConnectionFactory;
public class Send {
private final static String QUEUE_NAME = "hello";
public static void main(String[] argv) throws java.io.IOException {
ConnectionFactory factory = new ConnectionFactory();
factory.setHost("localhost");
Connection connection = factory.newConnection();
Channel channel = connection.createChannel();
channel.queueDeclare(QUEUE_NAME, false, false, false, null);
String message = "Hello World!";
channel.basicPublish("", QUEUE_NAME, null, message.getBytes());
System.out.println(" [x] Sent '" + message + "'");
channel.close();
connection.close();
}
}
I am not aware of making a socket connection, please let me know how to resolve this.
Here are the steps you should follow for your code to work:
Download and install the latest Erlang.
Download the RabbitMQ server.
Install RabbitMQ Server
Compile and run your code and it should work by now.
Hope this helps.
Related
I am running rabbitmq in my local mac in docker container. I accessed it through the GUI (at port 15672) in browser and created a queue, exchange and published some messages in the queue. I am trying to write a java application which can read the messages from the queue and print it in the console but I am running in to this error.
rjashnani-ltm:rabbitmq rjashnani$ java -cp .:amqp-client-5.7.1.jar:slf4j-api-1.7.26.jar:slf4j-simple-1.7.26.jar Recv
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:350)
I created docker container using this command
docker run -d --hostname my-rabbit --name some-rabbit2 -p 15672:15672 -p 5672:5672 rabbitmq:3-management
Here is my Java application code
import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.ConnectionFactory;
import com.rabbitmq.client.DeliverCallback;
public class Recv {
private final static String QUEUE_NAME = "test-queue";
public static void main(String[] argv) throws Exception {
ConnectionFactory factory = new ConnectionFactory();
factory.setHost("localhost");
factory.setPort(5762);
factory.setUsername("guest");
factory.setPassword("guest");
factory.setVirtualHost("/");
Connection connection = factory.newConnection();
Channel channel = connection.createChannel();
channel.queueDeclare(QUEUE_NAME, false, false, false, null);
System.out.println(" [*] Waiting for messages. To exit press CTRL+C");
DeliverCallback deliverCallback = (consumerTag, delivery) -> {
String message = new String(delivery.getBody(), "UTF-8");
System.out.println(" [x] Received '" + message + "'");
};
channel.basicConsume(QUEUE_NAME, true, deliverCallback, consumerTag -> { });
}
}
docker run -it --rm --name rabbitmq -p 5672:5672 -p 15672:15672 rabbitmq:3-management
Running docker with -it argument, resolved the issue.
I am attempting to connect to an Oracle database through Java with the Oracle JDBC driver with the following code (obscuring the host, service, user, and password):
import java.sql.*;
public class Main {
public Main () {
try {
String host = "HOST_NAME";
String port = "1521";
String service = "SERVICE_NAME";
String user = "SCHEMA_USER";
String password = "SCHEMA_PASSWORD";
Class.forName("oracle.jdbc.driver.OracleDriver");
Connection connection = DriverManager.getConnection("jdbc:oracle:thin:#(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=" +
host +
")(PORT=" +
port +
")))(CONNECT_DATA=(SERVICE_NAME=" +
service +
")))",
user,
password);
connection.close ();
} catch (Exception e) {
e.printStackTrace();
}
}
public static void main (String args) {
new Main ();
}
}
However, I receive the following error:
java.sql.SQLException: IO Error: The Network Adapter could not establish the connection
at oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:458)
at oracle.jdbc.driver.PhysicalConnection.<init>(PhysicalConnection.java:546)
at oracle.jdbc.driver.T4CConnection.<init>(T4CConnection.java:236)
at oracle.jdbc.driver.T4CDriverExtension.getConnection(T4CDriverExtension.java:32)
at oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:521)
at java.sql.DriverManager.getConnection(Unknown Source)
at java.sql.DriverManager.getConnection(Unknown Source)
at com.acxiom.axle.reporting.database.DatabaseConnection.connect(DatabaseConnection.java:23)
at com.acxiom.axle.reporting.Reporting.establishDatabaseConnection(Reporting.java:53)
at com.acxiom.axle.reporting.Reporting.beginReporting(Reporting.java:20)
at com.acxiom.axle.reporting.Entry.<init>(Entry.java:28)
at com.acxiom.axle.reporting.Entry.main(Entry.java:118)
Caused by: oracle.net.ns.NetException: The Network Adapter could not establish the connection
at oracle.net.nt.ConnStrategy.execute(ConnStrategy.java:392)
at oracle.net.resolver.AddrResolution.resolveAndExecute(AddrResolution.java:434)
at oracle.net.ns.NSProtocol.establishConnection(NSProtocol.java:687)
at oracle.net.ns.NSProtocol.connect(NSProtocol.java:247)
at oracle.jdbc.driver.T4CConnection.connect(T4CConnection.java:1102)
at oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:320)
... 11 more
Caused by: java.net.UnknownHostException: null
at java.net.Inet6AddressImpl.lookupAllHostAddr(Native Method)
at java.net.InetAddress$2.lookupAllHostAddr(Unknown Source)
at java.net.InetAddress.getAddressesFromNameService(Unknown Source)
at java.net.InetAddress.getAllByName0(Unknown Source)
at java.net.InetAddress.getAllByName(Unknown Source)
at java.net.InetAddress.getAllByName(Unknown Source)
at oracle.net.nt.TcpNTAdapter.connect(TcpNTAdapter.java:117)
at oracle.net.nt.ConnOption.connect(ConnOption.java:133)
at oracle.net.nt.ConnStrategy.execute(ConnStrategy.java:370)
... 16 more
The strange thing is, I can connect to the database from PL/SQL Developer, I can ping the remote host, and I can telnet to the remote host on port 1521.
Why would only Java appear to give an UnknownHostException, but I can connect and ping the host with other applications?
EDIT: I removed "hr/hr" from the connection string above. I have tried the connection as-is with it removed and still receive the same error. I've also tried changing the connection string to match the version morgano listed in his answer, with the same result. Finally, I tried to change the port number to a port I know it's not listening on, and it still receives the same error.
The connection string is of the correct format. The problem is that the host isn't set. It's null, or perhaps the string "null". There's simply no other way to generate the error message java.net.UnknownHostException: null
In your sample code, you write String host = "HOST_NAME";. This makes it look like in your real code you are assigning a constant string to the variable host. However, I'm going to stick my neck out and say that in your real code you are not doing this. You are looking up the host name from somewhere, this lookup fails for some reason, you don't check this, and hence you pass a null value into the connection string.
Your JDBC url is wrong, according to the documentation it should be something like:
jdbc:oracle:driver_type:[username/password]#//host_name:port_number/service_name
In your case your code would be something like:
import java.sql.*;
public class Main {
public Main () {
try {
String host = "HOST_NAME";
String port = "1521";
String service = "SERVICE_NAME";
String user = "SCHEMA_USER";
String password = "SCHEMA_PASSWORD";
Class.forName("oracle.jdbc.driver.OracleDriver");
Connection connection = DriverManager.getConnection(
"jdbc:oracle:thin:#//" + host
+ ":" + port + "/" + service, user, password);
connection.close ();
} catch (Exception e) {
e.printStackTrace();
}
}
public static void main (String args) {
new Main ();
}
}
I am new to RabbitMQ and trying out simple example on it.
Below is my java source:
import com.rabbitmq.client.ConnectionFactory;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.Channel;
public class Send {
private final static String QUEUE_NAME = "hello";
public static void main(String[] argv) throws Exception {
ConnectionFactory factory = new ConnectionFactory();
factory.setHost("localhost");
Connection connection = factory.newConnection();
Channel channel = connection.createChannel();
channel.queueDeclare(QUEUE_NAME, false, false, false, null);
String message = "Hello World!";
channel.basicPublish("", QUEUE_NAME, null, message.getBytes());
System.out.println(" [x] Sent '" + message + "'");
channel.close();
connection.close();
}
}
And am getting below error:
Exception in thread "main" java.net.ConnectException: Connection refused: connect
at java.net.DualStackPlainSocketImpl.connect0(Native Method)
at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:79)
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.PlainSocketImpl.connect(PlainSocketImpl.java:172)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
at java.net.Socket.connect(Socket.java:579)
at com.rabbitmq.client.impl.FrameHandlerFactory.create(FrameHandlerFactory.java:32)
at com.rabbitmq.client.ConnectionFactory.newConnection(ConnectionFactory.java:588)
at com.rabbitmq.client.ConnectionFactory.newConnection(ConnectionFactory.java:612)
at .Send.main(Send.java:15)
Any suggestions please?
Do you have your RabbitMQ server installed?
Also do you have the rabbitmq-client.jar and its dependencies on the classpath?
Try running this from your terminal:
java -cp .:commons-io-1.2.jar:commons-cli-1.1.jar:rabbitmq-client.jar Send
I am trying to fetch and download file in html format. Following is the code block:
import java.net.*;
import java.io.*;
public class URLReader {
public static void main(String[] args) throws Exception {
System.setProperty("http.proxyHost", "webcache.mydomain.com");
System.setProperty("http.proxyPort", "8080");
URL url = new URL("http://www.java2s.com/");
BufferedReader in = new BufferedReader(new InputStreamReader(url.openStream()));
String inputLine;
while ((inputLine = in.readLine()) != null)
System.out.println(inputLine);
in.close();
}
}
Here, when i am trying to Run this java file it show me following error:
D:\Build>javac URLReader.java
D:\Build>java URLReader
Exception in thread "main" java.net.ConnectException: Connection timed out: connect
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 java.net.Socket.connect(Socket.java:478)
at sun.net.NetworkClient.doConnect(NetworkClient.java:163)
at sun.net.www.http.HttpClient.openServer(HttpClient.java:388)
at sun.net.www.http.HttpClient.openServer(HttpClient.java:523)
at sun.net.www.http.HttpClient.<init>(HttpClient.java:227)
at sun.net.www.http.HttpClient.New(HttpClient.java:300)
at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:977)
at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:925)
at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:836)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1172)
at java.net.URL.openStream(URL.java:1010)
at URLReader.main(URLReader.java:12)
I don't think there any problem with code because When i tried to run this code at Home it worked for me. But when i tried it in my office it showed me the error!
So i guess there must be some kind of blockage in my office.
Can i set any proxy here in code so that it might work?
If you are behind a proxy you need to configure Java to use it. Read here on how to set your proxy for your network program
Try this as mentioned in this link http://docs.oracle.com/javase/6/docs/technotes/guides/net/proxies.html
//Set the http proxy to webcache.mydomain.com:8080
System.setProperty("http.proxyHost", "webcache.mydomain.com");
System.setPropery("http.proxyPort", "8080");
// Next connection will be through proxy.
URL url = new URL("http://java.sun.com/");
InputStream in = url.openStream();
// Now, let's 'unset' the proxy.
System.setProperty("http.proxyHost", null);
// From now on http connections will be done directly.
I am communicating using TCP Socket.
While Working, a problem arises
Client can't make 'Socket' Instance.
Strange Point is that (In Server using Python)
Using 'socket' class in python don't cause problem,
but using 'SocketServer.TCPServer' class in python cause problem
This is my environment.
Server : Python
Client : Java / Many Users will try connect.
Server Code (using Python):
SooMain.py
if name == "main":
server = SooServer('localhost', PORT_DEBUG, SooRequestHandler)
server.serve_forever()
SooServer.py
class SooServer(SocketServer.TCPServer):
"This is Server For Project201201"
def __init__(self,
host='localhost',
port=PORT_DEBUG,
handler=SooRequestHandler):
#SocketServer.ThreadingTCPServer.__init__(self, (host, port), handler)
SocketServer.TCPServer.__init__(self, (host, port), handler)
print "SooServer <State> __init__"
self.abort=0
self.timeout=10
def shutdown(self):
SocketServer.ThreadingTCPServer.shutdown(self)
print "SooServer <State> shutdown"
Client Code (using Java):
TestJava.java
public class TestJava {
public static void main(String[] args) throws Exception{
// TODO Auto-generated method stub
try {
String[] aStrData = {
"Test",
"Test" };
InetAddress m_oInetAddr = InetAddress.getByName(DEBUG_ADDR);
Socket m_oSocket = new Socket(m_oInetAddr, DEBUG_PORT); //This Line Makes Exception!!!!!
PrintWriter out =
new PrintWriter(
new BufferedWriter(
new OutputStreamWriter(m_oSocket.getOutputStream())), true);
int nNumData = aStrData.length;
out.println(Integer.toString(nNumData));
for (int i=0 ; i<nNumData ; i++) {
out.println(aStrData[i]);
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
Error Code (using Java):
Releated Line : Socket m_oSocket = new Socket(m_oInetAddr, DEBUG_PORT);
java.net.ConnectException: Connection refused
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:241)
at TestJava.main(TestJava.java:51)