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Server sends "ping request" to client in a single URL using JAX-RS and RESTeasy

I would like to create a web application that is able to "ping" the client once the client has accessed certain URL (e.g. www.example.com/ping/hello) in order to get the round trip time between server and client. And by "ping" request i mean a simple request with a timestamp from server and client sends back response with its timestamp. I was hoping for this activity to be done with a single URL if possible.
The flow is something like this:
Client goes to the URL
Server sends the response to the client with its timestamp
Client then sends another response to server with new timestamp
Server finally concludes the connection with 200 OK
So far I've only been able to do the first and second steps but not sure how to ensure client to go to the same URL again without back to the first step.
My server code is something like this:
#GET
#Path("/helloping")
public Response getPingServerClient(#Context HttpServletRequest req) {
String result = Long.toString(System.currentTimeMillis());
return Response.status(200).entity(result).build();
//the code to receive the response from client containing timestamp
}
Is there a way to do that?

There are two client to server calls. You'll have to figure out a way to differentiate between these two calls.
I can think of 3 options for this purpose:
HTTP header
Query parameter in GET request
POST request with a marker to differentiate the two calls
The request/response flow will be something like this:
Client -> Server : Request
Server -> Client : Response with timestamp t1
Client -> Server : Request with timestamp t2 and the above mentioned marker
Server -> Client : Response 200
In this approach, you'll have to write custom code at both server and client side to handle the mentioned logic.

I'm not a fan of what you are proposing because you're basically forcing the client to setup up code to effectively become a server, itself. This is inconvenient for the client.
Instead, consider a ping-pong approach where the client first calls the server's ping endpoint, which returns the server's timestamp. As soon as the client obtains the server's ping response, the client is instructed to call a second pong method, which accepts the new timestamp.
It's easier and simpler to require the client to call web service methods than it is to force to client to become a pseudo server. Hence the recommendation.

Java Server Side: send Http POST response - status only

Some third party is sending an Http Post request whenever something changes in their DB (e.g. when a contact has been updated, they send the contactID and 'contact_updated'). I have build a socket listener that catches those requests and is able to parse the information. However, I just can't get it to work to send back a response with the status '200 - OK'. Thus, the server on the client side keeps on trying (four times or so) to re-send the request.
Is there any, simple way to just send the response status without the need of adding external libs etc.?

It should be enough to send the string HTTP/1.1 200 OK back in your socket-listener.
If you have troubles, you can check out this answer, it shows how to use a HttpServer in Java just via plain JavaSE features.

Use
response.setStatus(HttpServletResponse.SC_OK);
to set the status code in your response header.
You may also set the content type.
response.setContentType("text/html;charset=UTF-8");

how to parse response when sending HTTP request manually through socket

This example:
Send HTTP Request manually via socket
describes very well how to send an HTTP request manually using a socket.
For sending, that's exactly what I need.
However, I could use some help with parsing the response. I.e. instead of having to deal with the flat response LOB I'd like to be able to invoke something like:
Response response = new Response(inputStream);
I looked at a few HTTP/Web service clients like JAX-RS or Apache Http Components that return a parsed response object but looks like they all expect the request to be submitted through the appropriate API.

An easy way to detect the end of http response (raw socket, java)?

I want to retrieve the server's response as is, with all headers. The first thing that comes to mind is to use raw sockets. As I have learned from the search, there are 3 ways to indicate the end of response:
(1) closing the connection;
(2) examining Content-Length;
(3) getting all chunks in the case of Transfer-Encoding: Chunked.
There is also
(4) the timeout method: assume that the timeout means end of data, but the latter is not really reliable.
I want a general-case solution and do not want to
add a Connection: close line to the request itself.
In addition, it is recommended to use an existing library rather than re-invent the wheel.
Question:
How do I use an existing package, preferably, something already present in Android, to detect the end of HTTP response while having access (without interference) to the raw data stream?
UPD: forgot to mention that the HTTP request is given to me as a sequence of bytes. Yes, it is for testing.
PS
relevant reading:
End of an HTTP Response
Detect the end of an HTTP Request in Java
Detect end of HTTP request body
How HTTP Server inform its clients that the response has ended
Proper handling of chuncked Http Response within Socket
Detect the end of a HTTP packet
Android socket & HTTP response headers
Java HTTP GET response waits until timeout

I suggest to use a the Apache HTTP client package (http://hc.apache.org/httpclient-3.x/ ) so you don't need to implement all the finicky details of the HTTP protocol.
The Apache Http Client will give you access to the headers and their content, which may be enough for you.
If you really need access to the actual character sequence sent by the server (e.g. for debugging purposes), you could then intercept the communication by replacing the connection socket factory with your own to create "intercepting" sockets which store all data transferred in a buffer where your code can access it later on. See http://hc.apache.org/httpcomponents-client-4.3.x/tutorial/html/connmgmt.html#d5e418

SOAP web service calls from Javascript

I'm struggling to successfully make a web service call to a SOAP web service from a web page. The web service is a Java web service that uses JAX-WS.
Here is the web method that I'm trying to call:
#WebMethod
public String sayHi(#WebParam(name="name") String name)
{
System.out.println("Hello "+name+"!");
return "Hello "+name+"!";
}
I've tried doing the web service call using the JQuery library jqSOAPClient (http://plugins.jquery.com/project/jqSOAPClient).
Here is the code that I've used:
var processResponse = function(respObj)
{
alert("Response received: "+respObj);
};
SOAPClient.Proxy = url;
var body = new SOAPObject("sayHi");
body.ns = ns;
body.appendChild(new SOAPObject("name").val("Bernhard"));
var sr = new SOAPRequest(ns+"sayHi",body);
SOAPClient.SendRequest(sr,processResponse);
No response seems to be coming back. When in jqSOAPClient.js I log the xData.responseXML data member I get 'undefined'. In the web service I see the warning
24 Mar 2011 10:49:51 AM com.sun.xml.ws.transport.http.server.WSHttpHandler handleExchange
WARNING: Cannot handle HTTP method: OPTIONS
I've also tried using a javascript library, soapclient.js (http://www.codeproject.com/kb/Ajax/JavaScriptSOAPClient.aspx). The client side code that I use here is
var processResponse = function(respObj)
{
alert("Response received: "+respObj);
};
var paramaters = new SOAPClientParameters();
paramaters.add("name","Bernhard");
SOAPClient.invoke(url,"sayHi",paramaters,true,processResponse);
I've bypassed the part in soapclient.js that fetches the WSDL, since it doesn't work
(I get an: IOException: An established connection was aborted by the software in your host machine on the web service side). The WSDL is only retrieved for the appropriate name space to use, so I've just replaced the variable ns with the actual name space.
I get exactly the same warning on the web service as before (cannot handle HTTP method: OPTIONS) and in the browser's error console I get the error "document is null". When I log the value of req.responseXML in soapclient.js I see that it is null.
Could anyone advise on what might be going wrong and what I should do to get this to work?

I found out what was going on here. It is the same scenario as in this thread: jQuery $.ajax(), $.post sending "OPTIONS" as REQUEST_METHOD in Firefox.
Basically I'm using Firefox and when one is doing a cross domain call (domain of the address of the web service is not the same as the domain of the web page) from Firefox using AJAX, Firefox first sends an OPTIONS HTTP-message (before it transmits the POST message), to determine from the web service if the call should be allowed or not. The web service must then respond to this OPTIONS message to tell if it allows the request to come through.
Now, the warning from JAX-WS ("Cannot handle HTTP method: OPTIONS") suggests that it won't handle any OPTIONS HTTP-messages. That's ok - the web service will eventually run on Glassfish.
The question now is how I can configure Glassfish to respond to the OPTIONS message.
In the thread referenced above Juha says that he uses the following code in Django:
def send_data(request):
if request.method == "OPTIONS":
response = HttpResponse()
response['Access-Control-Allow-Origin'] = '*'
response['Access-Control-Allow-Methods'] = 'POST, GET, OPTIONS'
response['Access-Control-Max-Age'] = 1000
response['Access-Control-Allow-Headers'] = '*'
return response
if request.method == "POST":
# ...
Access-Control-Allow-Origin gives a pattern which indicates which origins (recipient addresses) will be accepted (mine might be a bit more strict than simply allowing any origin) and Access-Control-Max-Age tells after how many seconds the client will have to request permission again.
How do I do this in Glassfish?

Have you actually tested that ws is working properly?
You can use SoapUI for inspecting request/response etc.
When you confirm that ws is working from SoapUI, inspect what is format of raw Soap message. Then try to inspect how it looks before sending with .js method, and compare them.
It might help you understand what is wrong.

Check if this helps
http://bugs.jquery.com/attachment/ticket/6029/jquery-disable-firefox3-cross-domain-magic.patch
it's marked as invalid
http://bugs.jquery.com/ticket/6029
but it might give you some hint
On the other hand, instead to override proper settings for cross-domain scripting might be better if you can create and call local page that will do request to ws and return result.
Or even better, you can create page that will receive url as param and do request to that url and just return result. That way it will be more generic and reusable.