Develop Reference

java.net.URLConnection fails to connect via http or https

I am debugging an issue with my local Fiji/ImageJ installation failing to update through the Help -> Update UI. The ImageJ code that triggers the issue is this updater code: https://github.com/imagej/imagej-ui-swing/blob/78a3180b6bc830166d15c73a01443c7a642c3908/src/main/java/net/imagej/ui/swing/updater/ImageJUpdater.java#L360-L370
I wrote minimal test case to reproduce this pointing JAVA_HOME at the Fiji/ImageJ application (/Applications/Fiji.app/java/macosx/zulu8.60.0.21-ca-fx-jdk8.0.322-macosx_x64/jre/Contents/Home).
import java.net.URL;
import java.net.URLClassLoader;
import java.net.URLConnection;
import java.io.IOException;
import java.net.HttpURLConnection;
class HelloWorld {
public static void main(String[] args) {
try {
final URL url = new URL("http://neverssl.com");
final URLConnection urlConn = url.openConnection();
final HttpURLConnection httpConn = (HttpURLConnection) urlConn;
final int code = httpConn.getResponseCode();
} catch (IOException ioe) {
ioe.printStackTrace();
}
}
}
This code results in the following error:
java.io.IOException: Error writing to server
at sun.net.www.protocol.http.HttpURLConnection.writeRequests(HttpURLConnection.java:705)
at sun.net.www.protocol.http.HttpURLConnection.writeRequests(HttpURLConnection.java:717)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1598)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1505)
at java.net.HttpURLConnection.getResponseCode(HttpURLConnection.java:480)
at HelloWorld.main(HelloWorld.java:14)
If I change the URL to an https URL, the error changes to
javax.net.ssl.SSLException: Couldn't kickstart handshaking
at sun.security.ssl.Alert.createSSLException(Alert.java:127)
at sun.security.ssl.TransportContext.fatal(TransportContext.java:348)
at sun.security.ssl.TransportContext.fatal(TransportContext.java:291)
at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:449)
at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:410)
at sun.net.www.protocol.https.HttpsClient.afterConnect(HttpsClient.java:559)
at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(AbstractDelegateHttpsURLConnection.java:197)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1577)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1505)
at java.net.HttpURLConnection.getResponseCode(HttpURLConnection.java:480)
at sun.net.www.protocol.https.HttpsURLConnectionImpl.getResponseCode(HttpsURLConnectionImpl.java:352)
at HelloWorld.main(HelloWorld.java:14)
Suppressed: 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.SSLSocketOutputRecord.encodeAlert(SSLSocketOutputRecord.java:81)
at sun.security.ssl.TransportContext.fatal(TransportContext.java:379)
... 10 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.SSLSocketOutputRecord.flush(SSLSocketOutputRecord.java:251)
at sun.security.ssl.HandshakeOutStream.flush(HandshakeOutStream.java:89)
at sun.security.ssl.ClientHello$ClientHelloKickstartProducer.produce(ClientHello.java:580)
at sun.security.ssl.SSLHandshake.kickstart(SSLHandshake.java:510)
at sun.security.ssl.ClientHandshakeContext.kickstart(ClientHandshakeContext.java:112)
at sun.security.ssl.TransportContext.kickstart(TransportContext.java:231)
at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:432)
... 8 more
Comparing a tcpdump filtered on the attempted host on this machine compared to a working one, I see early FIN packets being sent before any PSH packets are sent, so I think that is related to connections closing early.
On another machine running the same OS X version, I ran the same snippet pointing JAVA_HOME at the same directory, and had no issues.

java.rmi.ConnectException: Connection refused to host: 127.0.0.1

I've tried to used RMI, here is server side. at first it worked without any exception, but now after three times whenever i try to run the below code, i will get some errors
The code is:
import java.rmi.server.UnicastRemoteObject;
/**
* Created by elyas on 12/11/14 AD.
*/
public class LogicImplement extends UnicastRemoteObject implements Logic
{
public LogicImplement() throws Exception
{
java.rmi.registry.LocateRegistry.createRegistry(6060);
java.rmi.Naming.rebind("Object1",this);
}
#Override
public int sum(int a, int b) throws Exception
{
int result = a + b;
System.out.println("ana sum executed");
return result;
}
public static void main(String[] args)
{
try
{
LogicImplement logicImplement = new LogicImplement();
} catch (Exception e)
{
e.printStackTrace();
}
}
}
The error is like this: i've tried to change the Object1 to for example Object2, but again i will get error, also i change the port number...
what is solution?
java.rmi.ConnectException: Connection refused to host: 127.0.0.1; 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:341)
at sun.rmi.registry.RegistryImpl_Stub.rebind(Unknown Source)
at java.rmi.Naming.rebind(Naming.java:177)
at LogicImplement.<init>(LogicImplement.java:12)
at LogicImplement.main(LogicImplement.java:27)
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 com.intellij.rt.execution.application.AppMain.main(AppMain.java:120)
Caused by: 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:392)
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:147)
at sun.rmi.transport.tcp.TCPEndpoint.newSocket(TCPEndpoint.java:613)
... 12 more

java.net.ConnectException: Connection refused
There could be couple of reasons for this exception:
You have not started your rmiregistry in background.
You are trying to connect to the wrong port number.
Your firewall maybe blocking the connections.

The Answer was very simple, By default, the registry runs on port 1099. To start the registry on a different port, specify the port number on the command line. Do not forget to unset your CLASSPATH environment variable. for more information check this link: Running the Example Programs
** So for fixing this code i must change the port number form 6060 to 1099
notice that: if 1099 is used by other services you have to test 1100, and if 1100 is used too, you have yo use 1101 and so on. :-)

Since this was a port number issue, there is another way to start the registry on the port number you want:
java.rmi.registry.Registry rmiRegistry = java.rmi.registry.LocateRegistry.
createRegistry(6060); // Creates a registry on 6060
rmiRegistry.rebind("Object1",this); // Binds to registry created on 6060

You haven't started the RMI Registry.
When you get past this, if it still happens when calling the remote method, see item A.1 of the RMI FAQ.

java tutorial - unknown host exception

I'm trying to read a URL using the tutorial : http://docs.oracle.com/javase/tutorial/networking/urls/readingURL.html
import java.net.*;
import java.io.*;
public class URLReader {
public static void main(String[] args) throws Exception {
URL oracle = new URL("http://www.google.com/");
BufferedReader in = new BufferedReader(new InputStreamReader(oracle.openStream()));
String inputLine;
while ((inputLine = in.readLine()) != null)
System.out.println(inputLine);
in.close();
}
}
But I'm getting below exception. www.google.com is a known host ?
Exception in thread "main" java.net.UnknownHostException: www.google.com
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:195)
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:395)
at sun.net.www.http.HttpClient.openServer(HttpClient.java:530)
at sun.net.www.http.HttpClient.<init>(HttpClient.java:234)
at sun.net.www.http.HttpClient.New(HttpClient.java:307)
at sun.net.www.http.HttpClient.New(HttpClient.java:324)
at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:970)
at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:911)
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:8)

Are you running behind a proxy ?
The article seems to suggest there is a configuration needed in that case.
Alternatively, the program might hang or you might see an exception stack trace. If either of the latter two events occurs, you may have to set the proxy host so that the program can find the Oracle server.

Are you behind a proxy? Try to set the proxy in eclipse or try
java -DproxySet=true -DproxyHost=10.0.0.14 -DproxyPort=6588 JavApp

I think its network error check your internet Connection....

Connection timed out. Why? [duplicate]

This question already has answers here:
What is a connection timeout during a http request
(2 answers)
Closed last month.
I get an exception when I run this code. Why?
Exception in thread "main" java.net.ConnectException: Connection timed out: connect
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.URL;
public class MainClass {
public static void main(String[] args) throws Exception {
System.setProperty("java.protocol.handler.pkgs", "com.sun.net.ssl.internal.www.protocol");
URL url = new URL("https://www.verisign.com/");
BufferedReader in = new BufferedReader(new InputStreamReader(url.openStream()));
String line;
while ((line = in.readLine()) != null) {
System.out.println(line);
}
in.close();
}
}
Exception:
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: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 com.sun.net.ssl.internal.ssl.SSLSocketImpl.connect(SSLSocketImpl.java:550)
at com.sun.net.ssl.internal.ssl.BaseSSLSocketImpl.connect(BaseSSLSocketImpl.java:141)
at sun.net.NetworkClient.doConnect(NetworkClient.java:163)
at sun.net.www.http.HttpClient.openServer(HttpClient.java:394)
at sun.net.www.http.HttpClient.openServer(HttpClient.java:529)
at sun.net.www.protocol.https.HttpsClient.<init>(HttpsClient.java:272)
at sun.net.www.protocol.https.HttpsClient.New(HttpsClient.java:329)
at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.getNewHttpClient(AbstractDelegateHttpsURLConnection.java:172)
at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:801)
at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(AbstractDelegateHttpsURLConnection.java:158)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1049)
at com.sun.net.ssl.internal.www.protocol.https.HttpsURLConnectionOldImpl.getInputStream(HttpsURLConnectionOldImpl.java:204)
at java.net.URL.openStream(URL.java:1010)
at https.ssl.MainClass.main(MainClass.java:13)

We can't diagnose your networks for you. You need to do it yourself, or get your local admins to look at.
Things you should check before you bug your admins:
can you ping the host?
can you connect to http://www.verisign.com using a web browser?
can you connect to https://www.verisign.com using a web browser?
can you connect to http://www.verisign.com using your program?
can you connect to anything using your program?
The chances are that your problem is firewall related. My first guess would be that you don't have the correct environment variables or Java system properties set to tell the JVM to use a local proxy server for outgoing HTTP / HTTPS requests.
If it is not a problem with your settings, you will need to get help from someone local who can help you diagnose the problem.

java.net.SocketException: Software caused connection abort: connect [duplicate]

This question already has answers here:
java.net.SocketException: Software caused connection abort: recv failed, with java.net.SocketException: Connection reset [duplicate]
(3 answers)
Closed 9 years ago.
I am trying to programmatically (Java) open a URL that points to a modem on the network. I am connected to the network and can ping the device as well as fetch the URL within a browser. However, programmatically, I get the following stack trace when trying to open the connection.
java.net.SocketException: Software caused connection abort: 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:519)
at com.sun.net.ssl.internal.ssl.SSLSocketImpl.connect(SSLSocketImpl.java:550)
at com.sun.net.ssl.internal.ssl.BaseSSLSocketImpl.connect(BaseSSLSocketImpl.java:141)
at sun.net.NetworkClient.doConnect(NetworkClient.java:163)
at sun.net.www.http.HttpClient.openServer(HttpClient.java:394)
at sun.net.www.http.HttpClient.openServer(HttpClient.java:529)
at sun.net.www.protocol.https.HttpsClient.<init>(HttpsClient.java:272)
at sun.net.www.protocol.https.HttpsClient.New(HttpsClient.java:329)
at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.getNewHttpClient(AbstractDelegateHttpsURLConnection.java:172)
at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:793)
at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(AbstractDelegateHttpsURLConnection.java:158)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1041)
at sun.net.www.protocol.https.HttpsURLConnectionImpl.getInputStream(HttpsURLConnectionImpl.java:234)
Also, the URL uses the https protocol.
Here is my code:
try {
URL jipmURL = new URL("https://xxx.xxx.xxx.xxx/login.cgi");
URLConnection urlConnection = jipmURL.openConnection();
InputStreamReader streamReader = new InputStreamReader(
jipmURLConnection.getInputStream());
BufferedReader in = new BufferedReader(streamReader);
StringBuffer stringBuffer = new StringBuffer();
String inputLine;
while ((inputLine = in.readLine()) != null) {
stringBuffer.append(inputLine);
}
System.out.println("Results: " + stringBuffer);
in.close();
} catch (IOException e) {
e.printStackTrace();
}
Any help would be appreciated,
Steve

The exception message indicates that you're not even able to establish a TCP connection with the web server. It's difficult to guess what the exact problem is, since you're able to open the page from a browser, but could it simply be that you're running a software firewall, which refuses the Java process to connect to that address?