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Send data from php to java

I have found quite a lot of other posts on this topic but none seem to have the answer I need.
I have written a Bukkit plugin for Minecraft that can send post data to a PHP page and get a return from the page.
Now the one thing I can't figure out. I would like to have a button on the page, and when the button is clicked, send data to the Java plugin and have the plugin print the message.
I have seen something about sockets. But after reading about them I can't figure out how to set them up.
Pretty much at any time you should be able to click the button and it sends data to the Java plugin and I can use that data however I like.
Does anyone know how I can have the Java plugin constantly waiting for data from the page?
My current code:
(This sends the players name to the website.)
String re = "";
URL url = new URL("address here");
URLConnection con = url.openConnection();
con.setDoOutput(true);
PrintStream ps = new PrintStream(con.getOutputStream());
ps.print("player=" + player.getName());
con.getInputStream();
BufferedReader rd = new BufferedReader(new InputStreamReader(con.getInputStream()));
String line;
while ((line = rd.readLine()) != null) {
re += line + "\n";
}
rd.close();
ps.close();
And my php just returns any post data it gets.
It works fine, but I would like to listen in my java plugin for data from the php page.

There are many ways to make communication between two servers. I'd use one of them:
Sockets
JMS - Java Message Service such as ActiveMQ
Both of them have tutorials available, just google.

You could use a database, or setup a json/xml api on the PHP end, and access the database, or access the json/xml from Java with this example code to open the url.
URL url = new URL("site.com/api/foo.json");
try (BufferedReader reader = new BufferedReader(new InputStreamReader(url.openStream(), "UTF-8"))) {
for (String line; (line = reader.readLine()) != null;) {
System.out.println(line);
}
}
You can look at this tutorial to parse JSON with Java.

Taking text from a response web page using Java

I am sending commands to a server using http, and I currently need to parse a response that the server sends back (I am sending the command via the command line, and the servers response appears in my browser).
There are a lot of resources such as this: Saving a web page to a file in Java, that clearly illustrate how to scrape a page such as cnn.com. However, since this is a response page that is only generated when the camera receives a specific command, my attempts to use the method described by Mike Deck (in the link above) have met with failure. (Specifically, when my program requests the page again the server returns a 401 error.)
The response from the server opens a new tab in my browser. Essentially, I need to know how to save the current web page using java, since reading in a file is probably the most simple way to approach this. Do any of you know how to do this?
TL;DR How do you save the current webpage to a webpage.html or webpage.txt file using java?
EDIT: I used Base64 from the Apache commons codec, which solved my 401 authentication issue. However, I am still getting a 400 error when I attempt to connect my InputStream (see below). Does this mean a connection isn't being established in the first place?
URL url = new URL ("http://"+ipAddress+"/axis-cgi/record/record.cgi?diskid=SD_DISK");
byte[] encodedBytes = Base64.encodeBase64("root:pass".getBytes());
String encoding = new String (encodedBytes);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setRequestMethod("POST");
connection.setDoInput (true);
connection.setRequestProperty ("Authorization", "Basic " + encoding);
connection.connect();
InputStream content = (InputStream)connection.getInputStream();
BufferedReader in = new BufferedReader (new InputStreamReader (content));
String line;
while ((line = in.readLine()) != null) {
System.out.println(line);
}
EDIT 2: Changing the request to a GET resolved the issue.

So while scrutinizing my code above, I decided to change
connection.setRequestMethod("POST");
to
connection.setRequestMethod("GET");
This solved my problem. In hindsight, I think the server was not recognizing the HTTP because it is not set up to handle the various trappings that come along with post.

How to read JavaScript response from a URL in java

I need to write a simple java function that takes a URL and processes the response which is in JavaScript, I tried using HttpUrlConnection, but it could not. Is there any java library for handling javascript response?
thanks.
EDIT: My code:
Url url = new url("https://login.live.com/oauth20_authorize.srf");
HttpURLConnection con = (HttpURLConnection) url.openConnection();
BufferedReader reader = new BufferedReader( new InputStreamReader(url.openStream()));
while(reader.readLine()!=null){
System.out.println(reader.readLine());
Response:
<html dir="..... Windows Live ID requires JavaScript to sign in. This web browser either does not support JavaScript, or scripts are being blocked......<body onload="evt_LoginHostMobile_onload(event);">
But I want to read those javascript response. Is it possible in java?

I found the way, HtmlUnit does this, it can handle javascript response
Thanks all those negative raters .....

Download file programmatically

I am trying to download an vcalendar using a java application, but I can't download from a specific link.
My code is:
URL uri = new URL("http://codebits.eu/s/calendar.ics");
InputStream in = uri.openStream();
int r = in.read();
while(r != -1) {
System.out.print((char)r);
r = in.read();
}
When I try to download from another link it works (ex: http://www.mysportscal.com/Files_iCal_CSV/iCal_AUTO_2011/f1_2011.ics). Something don't allow me to download and I can't figure out why, when I try with the browser it works.

I'd follow this example. Basically, get the response code for the connection. If it's a redirect (e.g. 301 in this case), retrieve the header location and attempt to access the file using that.
Simplistic Example:
URL uri = new URL("http://codebits.eu/s/calendar.ics");
HttpURLConnection con = (HttpURLConnection)uri.openConnection();
System.out.println(con.getResponseCode());
System.out.println(con.getHeaderField("Location"));
uri = new URL(con.getHeaderField("Location"));
con = (HttpURLConnection)uri.openConnection();
InputStream in = con.getInputStream();

You should check what that link actually provides. For example, it might be a page that has moved, which gives you back an HTTP 301 code. Your browser will automatically know to go and fetch it from the new URL, but your program won't.
You might want to try, for example, wireshark to sniff the actual traffic when you do the browser request.

I think too that there is a redirect. The browser downloads from ssl secured https://codebits.eu/s/calendar.ics. Try using a HttpURLConnection, it should follow redirects automatically:
HttpURLConnection con = (HttpURLConnection)uri.openConnection();
InputStream in = con.getInputStream();

Downloading a web page with Android

I'm downloading a web page then extracting some data out of it, using regex (don't yell at me, I know a proper parser would be better, but this is a very simple machine generated page). This works fine in the emulator, and on my phone when connected by wi-fi, but not on 3G - the string returned is not the same, and I don't get a match. I can imagine it has something to do with packet size or latency, but I can't figure it out.
My code:
public static String getPage(URL url) throws IOException {
final URLConnection connection = url.openConnection();
HttpGet httpRequest = null;
try {
httpRequest = new HttpGet(url.toURI());
} catch (URISyntaxException e) {
e.printStackTrace();
}
HttpClient httpclient = new DefaultHttpClient();
HttpResponse response = (HttpResponse) httpclient.execute(httpRequest);
HttpEntity entity = response.getEntity();
BufferedHttpEntity bufHttpEntity = new BufferedHttpEntity(entity);
InputStream stream = bufHttpEntity.getContent();
String ct = connection.getContentType();
final BufferedReader reader;
if (ct.indexOf("charset=") != -1) {
ct = ct.substring(ct.indexOf("charset=") + 8);
reader = new BufferedReader(new InputStreamReader(stream, ct));
}else {
reader = new BufferedReader(new InputStreamReader(stream));
}
final StringBuilder sb = new StringBuilder();
String line;
while ((line = reader.readLine()) != null) {
sb.append(line);
}
stream.close();
return sb.toString();
}
Is it my poor connection causing this, or is there a bug in there? Either way, how do I solve it?
Update:
The file downloaded over 3G is 201 bytes smaller than the one over wi-fi. While they are obviously both downloading the correct page, the 3G one is missing a whole bunch of whitespace, and also some HTML comments that are present in the original page which I find a little strange. Does Android fetch pages differently on 3G as to reduce file size?

UserAgent (UA) shouldn't be changed if u access web page using 3g or wifi.
As it is mentioned before, get rid of UrlConnection, cause obviously code is complete for using HTTPClient method, and you are able to set UA using:
httpclient.getParams().setParameter(CoreProtocolPNames.USER_AGENT, userAgent);
last one..it might be silly but maybe web page is dynamic?! is that possible?

Here you go some hints, some of them silly hints, but just in case:
Review your mobile connection, try to open web browser, surf the web, and make sure it actually works
I don't know which is the web page your are trying to access but take into account that depending on your phone User Agent (UA), the rendered content might be different (web pages specially designed for mobile phones), or even no content rendered at all. Is it a web page on your own.
Try to access that same web page from Firefox, changing the UA (Use the User Agent Switcher for Firefox), and review the code returned.
That will be a good start point to figure out what's your problem
Ger

You may want to check if your provider has a transparent proxy in place with 3G.