Question

I’m not sure if what I’m trying to do is possible, it might not. Here is my problem:

I’m trying to use a Servlet to pass information from a client to a server via HTTP. This communication is very frequent (I’m passing UI information, so every single mouse event), so I want to have as little overhead as possible to avoid latency issues, which is why I would like to not do a GET call for each transmission. HTTP is a requirement. I’m using an older Tomcat version (Servlet API 2.4). I guess this is somewhat of a web sockets use case, but I don’t have any web sockets support available.

What I tried was to open a URL connection on the client side, and to open the input stream (otherwise the doGet() of the servlet never gets called). I’m passing an argument for initialization purposes to the client.

URLConnection uiConnection = url.openConnection();      
uiConnection.setRequestProperty("Authorization", "Basic " + encode("xyz" + ":"
            + "xyz"));
uiConnection.setReadTimeout(0);
uiConnection.setDoOutput(true);
uiConnection.setAllowUserInteraction(true);
DataInputStream is = new DataInputStream(
uiConnection.getInputStream());

When I later try to retrieve an ouput stream from this connection, I’m getting a ProtocolException (cannot write output after reading input).

out = new BufferedWriter(new OutputStreamWriter(
uiConnection.getOutputStream()));
out.write(uiUpdate);

On the servlet end I did something like this:

DataInputStream is = new DataInputStream(
            request.getInputStream());

Am I completely on the wrong track or is something like this possible without using a new connection for each transmission?

Thanks,
Mark

Answer 1

I think the key question for this, is do you also have http traffic going to this IP? If so, there may not be anything you can do using just java. If not, then create a servlet to listen in on port 80, and parse the incoming data directly.

http://download.oracle.com/javase/tutorial/networking/sockets/clientServer.html