Develop Reference

How to establish a FTPS data connection to a FileZilla Server 1.2.0

It is a known problem to use the Java FTPSClient of Apache commons-net with session resumption. Session resumption is a security feature which a FTPS server can require for data connections. The Apache FTPSClient does not support session resumption, and the JDK APIs make it hard to build a custom implementation. There are a couple of workarounds using reflection, see e.g. this answer and this commons-net bug entry.
I use such a workaround (see snipped below) in JDK 11 and tested it against a local FileZilla Server. It works with FileZilla Server 0.9.6, but it doesn't with FileZilla Server 1.2.0, which is the latest version at the time of writing. With that version, when trying to establish a data connection, the server responds with:
425 Unable to build data connection: TLS session of data connection not resumed.
As I said, FileZilla Server 0.9.6 is fine with how I do session resumption, and I made sure that the setting for requiring session resumption is activated.
In FileZilla Server 1.2.0, such settings are now set implicitly and cannot be changed via the GUI, maybe not at all. Are there some server settings that I can tweak for this to work? Or is it an issue with how I implemented the workaround? Does anyone experience similar issues?
This is the workaround I am using:
public class FTPSClientWithSessionResumption extends FTPSClient {
static {
System.setProperty("jdk.tls.useExtendedMasterSecret", "false");
System.setProperty("jdk.tls.client.enableSessionTicketExtension", "false");
}
#Override
protected void _connectAction_() throws IOException {
super._connectAction_();
execPBSZ(0);
execPROT("P");
}
#Override
protected void _prepareDataSocket_(Socket socket) throws IOException {
if (useSessionResumption && socket instanceof SSLSocket) {
// Control socket is SSL
final SSLSession session = ((SSLSocket)_socket_).getSession();
if (session.isValid()) {
final SSLSessionContext context = session.getSessionContext();
try {
final Field sessionHostPortCache = context.getClass().getDeclaredField("sessionHostPortCache");
sessionHostPortCache.setAccessible(true);
final Object cache = sessionHostPortCache.get(context);
final Method putMethod = cache.getClass().getDeclaredMethod("put", Object.class, Object.class);
putMethod.setAccessible(true);
Method getHostMethod;
try {
getHostMethod = socket.getClass().getMethod("getPeerHost");
}
catch (NoSuchMethodException e) {
// Running in IKVM
getHostMethod = socket.getClass().getDeclaredMethod("getHost");
}
getHostMethod.setAccessible(true);
Object peerHost = getHostMethod.invoke(socket);
InetAddress iAddr = socket.getInetAddress();
int port = socket.getPort();
putMethod.invoke(cache, String.format("%s:%s", peerHost, port).toLowerCase(Locale.ROOT), session);
putMethod.invoke(cache, String.format("%s:%s", iAddr.getHostName(), port).toLowerCase(Locale.ROOT), session);
putMethod.invoke(cache, String.format("%s:%s", iAddr.getHostAddress(), port).toLowerCase(Locale.ROOT), session);
}
catch (Exception e) {
throw new IOException(e);
}
}
else {
throw new IOException("Invalid SSL Session");
}
}
}
}
The address under which the socket is cached is determined using getPeerHost, getInetAddress().getHostName(), and getInetAddress().getHostAddress(). I tried several combinations of doing or not doing these three, but I always get the same result.
Edit:
Here is a screenshot of the server logs of the full session:

As stated in this StackOverflow post it is possible to tell the JVM that only TLS 1.2 should be used.
Here is the link to the original answer which worked for me: command for java to use TLS1.2 only
You have to add a command line parameter at the start of the JVM in this case this is: java -Djdk.tls.client.protocols=TLSv1.2 -jar ... <rest of command line here>
This simple parameter worked for me, now I can connect and transfer data from a FTP-Server wich runs FileZilla FTP-Server 1.3.0

BrowserMob Proxy’s - WebDriver / Error: The proxy server is refusing connections

I try to use BrowserMob Proxy’s with WebDriver. I use the next code:
public static void main(String[] args) throws Exception {
String strFilePath = "";
// start the proxy
ProxyServer server = new ProxyServer(4455);
server.start();
//captures the moouse movements and navigations
server.setCaptureHeaders(true);
server.setCaptureContent(true);
// get the Selenium proxy object
Proxy proxy = server.seleniumProxy();
// configure it as a desired capability
DesiredCapabilities capabilities = new DesiredCapabilities();
capabilities.setCapability(CapabilityType.PROXY, proxy);
// start the browser up
WebDriver driver = new FirefoxDriver(capabilities);
// create a new HAR with the label "apple.com"
server.newHar("assertselenium.com");
// open yahoo.com
driver.get("http://assertselenium.com");
driver.get("http://assertselenium.com/2012/10/30/transformation-from-manual-tester-to-a-selenium-webdriver-automation-specialist/");
// get the HAR data
Har har = server.getHar();
FileOutputStream fos = new FileOutputStream(strFilePath);
har.writeTo(fos);
server.stop();
driver.quit();
}
And I got the next error: The proxy server is refusing connections: Firefox is configured to use a proxy server that is refusing connections.
I try also to run the browsermob-proxy.bat with port 4455, and then I get the next error when I run the main:
java.net.BindException: Address already in use: JVM_Bind
How I can use BrowserMob Proxy’s?

The code for stating the proxy seems to be correct. For the BindException, it should be obvious that something is already using the port 4455. You can check it (on Windows machine, written from memory):
netstat -ano | find "4455"
in Linux use lsof -i:4455 to get the PID and kill it.
Anyway, for your proxy refusing connections, try setting the proxy explicitly, see if you have any luck, something like
proxy.setHttpProxy("localhost:4455");
proxy.setSslProxy("localhost:4455");
Also, make sure you are using up-to-date versions of FF and BMP.

java.net.BindException: Address already in use: JVM_Bind
You get this error because on the mentioned port there is already one server running. May be you run your code again without stopping the server you started it at first instance.

Try disabling internet explorer proxy on your pc.

Open browser with proxy setting set from Java

I need to open a browser from Java code. I understand this can be done as follows :
java.awt.Desktop.getDesktop().browse(java.net.URI.create("http://google.com"));
But i need the browser to use certain proxy settings as well. (i.e. when the browser opens, its proxy settings must be set to certain values.) I tried using the follwoing code but it doesnt work :
public static void main(String asf[]){
System.setProperty("java.net.useSystemProxies", "true");
System.setProperty("http.proxyHost", "127.0.0.1");
System.setProperty("http.proxyPort", "8080");
try {
java.awt.Desktop.getDesktop().browse(java.net.URI.create("http://google.com"));
} catch (IOException e) {
e.printStackTrace();
}
System.out.println("done");
}
Setting the proxy from command line using
java -Dhttp.proxyHost=webcache.example.com -Dhttp.proxyPort=8080
is not an option for me. How do i accomplish this?

Your code is largely correct which deals with setting the proxy, but in case it is not working there is another way to set the proxy via Java code and that is via the proxy class.
SocketAddress addr = new InetSocketAddress("socks.example.com", 1080);
Proxy proxy = new Proxy(Proxy.Type.SOCKS, addr);
Socket socket = new Socket(proxy);
InetSocketAddress dest = new InetSocketAddress("server.example.org", 1234);
socket.connect(dest);
Here the socket will try to connect to its destination address (server.example.org:1234) through the specified SOCKS proxy.
For more detail you can go through the Standard Java Documentation for Proxies
Your solution for opening a browser can be improved by adding a check
if(Desktop.isDesktopSupported())
{
Desktop.getDesktop().browse(new URI("http://www.google.com"));
}
this is in addition to your solution .... maybe you can call it an alternate way
try {
Process p=Runtime.getRuntime().exec("cmd /c start http://www.google.com");
}
catch(IOException e1) {
System.out.println(e1);
}

The Google Chromes proxy switches can be useful here. We can just make a shortcut for the chrome browser whose target contains the switch --proxy-server=127.0.0.1:8080 . Now this shortcut can be opened from java code using the Runtime class' exec method. The arguments to exec will be "cmd /c start /d \"d:\" chrome.lnk" where d: is the path of my shortcut. A detailed description of this technique can be found here http://sleepingthreads.blogspot.in/2013/07/open-browser-with-proxy-settings-set.html
Note that Google states that the use of switches is not recommended. So use this as a temporary solution only.

WebSockets, GlassFish, Grizzly -- can't connect

I am trying to get started with WebSockets, and trying to write a simple application to send messages back and forth via a websoket.
However, it looks like the socket that I am trying to create never gets connected. Why can that be?
Below is the code of my WebSockets class. When .onConnect() is called, it logs:
I am socket, I was connected. Am i connected? - false
Update: in JavaScript, where I create the socket in question, the readyState is 1, which means "socket open, communication is possble".
import a.b.Misc; //writes logs.
import com.sun.grizzly.websockets.BaseServerWebSocket;
import com.sun.grizzly.websockets.DataFrame;
import com.sun.grizzly.websockets.WebSocketListener;
public class ChatWebSocket_v2 extends BaseServerWebSocket {
private String user;
public ChatWebSocket_v2(WebSocketListener... listeners) {
super(listeners);
}
public String getUser() {
if (user == null) {
Misc.print("User is null in ChatWebSocket");
throw new NullPointerException("+=The user is null in chat web socket");
}
return user;
}
public void setUser(String user) {
Misc.print("Just set user: " + user);
this.user = user;
}
#Override
public void onMessage(String message) {
Misc.print(message +"\n");
}
#Override
public void onMessage(byte[] message) {
Misc.print(new String(message) +" << Bytes\n");
}
#Override
public void onConnect() {
Misc.print("I am socket, i was connected. Am i connected? - " + this.isConnected());
}
#Override
public void onClose(DataFrame df) {
Misc.print("I am socket, i was closed");
}
}

If you're just trying to make a connection somewhere, you might want to try this instead. There is a live working demo and you can download the javascript code and play with it yourself. Note that the javascript code only works if you have it installed on a server (due to browser security because it's 'fancy'.) There is also a step by step browser-based client tutorial in the works that I will post as soon as it's ready. Most proxy servers haven't been upgraded to handle websockets so they will screw up connection request and most people won't be able to connect to websocket servers from work. Firefox 7 (release) or Google Chrome 14 or later support the latest version of the websocket protocol that the demo server runs.
If you want to try to get the grizzly demo working, you might have some debugging to do and maybe I'll help with that. Note that in comments below the article, other people said they couldn't get it working either and I haven't found any follow up. At this point it seems no better than the echo app above even if we do get it running and is possibly overly complicated and underly documented if you're just trying to get started. But if you want to try to get it running, you should 'git' the latest version of the code here, which was at least committed recently and may be fixed.
Then make sure that app.url in the application javascript file is set to your installation directory. His is hard-coded as:
url: 'ws://localhost:8080/grizzly-websockets-chat/chat',
If you're using Firefox 7, the javascript needs to be modified to use the Moz prefix, for example:
if (typeof MozWebSocket != "undefined") { // window.MozWebSocket or "MozWebSocket" in window
ok
} else if (window.WebSocket) { // he uses if ("WebSocket" in window)
ok
} else {
do your print "browser doesn't support websockets"
}
.... then if the browser supports websockets
websocket = new WebSocket(app.url); or
websocket = new MozWebSocket(app.url);
// depending on which it is.
The HLL websocket server demo code has this all sorted out.
(another) UPDATE: As I work through grizzly myself, I found on the Quick Start in the glassfish admin console, there's a hello sample that's pretty easy to set up and run. You'll find instructions there. The sample directory also contains a war file named: websocket-mozilla; so I guess its supposed to use websockets. Someone who's familiar with jsp should review the source code. All I can see is that it's using an http session. No mention of a websocket at all. It's a lot like the hello sample.

How to get proxy settings from system settings in Java

I'm looking form way how to get system proxy information in Java under Windows, but I've found just one way. But it does not work for me.
public static void main(String[] args) throws Throwable {
System.setProperty("java.net.useSystemProxies", "true");
System.out.println("detecting proxies");
List<Proxy> pl = ProxySelector.getDefault().select(new URI("http://ihned.cz/"));
for (Proxy p : pl)
System.out.println(p);
Proxy p = null;
if (pl.size() > 0) //uses first one
p = pl.get(0);
System.out.println(p.address());
System.out.println("Done");
}
When I run the program, I get:
detecting proxies
DIRECT
null
Done
Java means, that I'm situated directly on internet. But it's wrong. I'm behind proxy. I'm unable to get the solution for my computer.

As we discussed in the comments the proxy settings is just applied for some of browsers you use.
If you want Java to use the same settings you need to manually put it into the java network settings (check this web page for details).

Thanks to Dacwe. The problem is, that browser does not use any system proxy, but it sets proxy self using a script. Thus there are not any proxies in the system and Java cannot reach them.