Re: gwt-comet - CometException: EventSource error
Hi Did you get a solution to this problem i have a similar problem On Friday, November 16, 2012 at 1:32:58 PM UTC+3, Magnus wrote: > > Hello, > > I would like to use "gwt-comet": > http://code.google.com/p/gwt-comet/ > > To get started, I tested the chat application provided with on the project > site: > http://code.google.com/p/gwt-comet/wiki/ChatExample > > I also got the example running: It works fine within eclipse and with GWT > development mode. > > Then, I deployed it as a war file to my tomcat 6 server, and I receive > this error repeatedly within the chat window: > error false net.zschech.gwt.comet.client.CometException: EventSource error > > Does anyone have an idea what could be the cause? > How are your experiences with gwt-comet? > > Thanks > Magnus > -- You received this message because you are subscribed to the Google Groups "GWT Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to google-web-toolkit+unsubscr...@googlegroups.com. To post to this group, send email to google-web-toolkit@googlegroups.com. Visit this group at https://groups.google.com/group/google-web-toolkit. For more options, visit https://groups.google.com/d/optout.
Usage of gwt-comet on gwt RequestFactory?
1- I have already used the following frameworks (Event based client-server) on GWT projects, and works fine with RPC call architecture. - GWT-Comet https://code.google.com/p/gwt-comet/ - GwtEventService https://code.google.com/p/gwteventservice/ After searching, i found a lot of frameworks that treat the client server messaging exchange problem: *2- Jboss Errai framework http://errai.github.io/* Great messaging service but i've not used it. I searched for only errai bus usage with gwt but nothing founded. *3- Atmosphere Framework https://github.com/Atmosphere/atmosphere* Seem to do same thing like comet but i've not used it. http://async-io.org/tutorial.html *4- WebSocket http://www.websocket.org/* *5- Spring-Integration-Cometdhttp://cometd.org/documentation/cometd-java/server/services/integration-spring * *6- Spring WebSockethttp://spring.io/blog/2013/07/24/spring-framework-4-0-m2-websocket-messaging-architectures/ * NOW : I want to develop a project with Spring roo and GWT. As Spring roo gwt based on RequestFactory architecture. I think that we can use Comet or gwteventservice with RequestFactory architecture, but we needAutoBeanhttps://code.google.com/p/google-web-toolkit/wiki/AutoBean to generate client side Entity interface on server side. *My question concern GWT RequestFactory :* How to integrate one of the frameworks above in gwt projects based on RequestFactory architecture? Is there any example ?! Thanks -- You received this message because you are subscribed to the Google Groups Google Web Toolkit group. To unsubscribe from this group and stop receiving emails from it, send an email to google-web-toolkit+unsubscr...@googlegroups.com. To post to this group, send email to google-web-toolkit@googlegroups.com. Visit this group at http://groups.google.com/group/google-web-toolkit. For more options, visit https://groups.google.com/groups/opt_out.
Re: gwt-comet issue with GWT 2.5
I'm having the exact same problem. I went further and downloaded the source, but its not documented at all and seems to reference several classes underneath com.sun.* packages which are not available to modern JDKs. On Saturday, 12 January 2013 16:05:42 UTC, Aldo wrote: Hi All I know this is not a GWT direct issue, but I was not able to find a solution for the problem, so maybe someone out there already dealt with this problem. I'm using gwt-comet project and it has been working perfectly so far, but now that I'm upgrading to GWT 2.5 I'm getting an error ( http://code.google.com/p/gwt-comet/issues/detail?id=33). I need to know if there is a solution (a JAR available compiled with GWT 2.5) or if anyone suggest a different project so I can replace the gwt-comet. Thanks in advance, Aldo -- You received this message because you are subscribed to the Google Groups Google Web Toolkit group. To unsubscribe from this group and stop receiving emails from it, send an email to google-web-toolkit+unsubscr...@googlegroups.com. To post to this group, send email to google-web-toolkit@googlegroups.com. Visit this group at http://groups.google.com/group/google-web-toolkit?hl=en. For more options, visit https://groups.google.com/groups/opt_out.
Re: gwt-comet issue with GWT 2.5
The most easy workaround is probably to download the CometSerializerGenerator.java from the issue you have mentioned and put it into your app's project into the correct package. Then as long as your classes/output folder is before gwt-comet.jar in your classpath the GWT compiler should pick up the generator from your app's project instead of gwt-comet.jar. Alternative is to rebuild gwt-comet from source and replace the file beforehand. -- J. -- You received this message because you are subscribed to the Google Groups Google Web Toolkit group. To unsubscribe from this group and stop receiving emails from it, send an email to google-web-toolkit+unsubscr...@googlegroups.com. To post to this group, send email to google-web-toolkit@googlegroups.com. Visit this group at http://groups.google.com/group/google-web-toolkit?hl=en. For more options, visit https://groups.google.com/groups/opt_out.
GWT comet in push server mode?
Hi, I have used comet library http://code.google.com/p/gwt-comet/wiki/GettingStarted to create a application. I would like to use comet to server pushes data to my client. Is it possible? Regards, -- You received this message because you are subscribed to the Google Groups Google Web Toolkit group. To unsubscribe from this group and stop receiving emails from it, send an email to google-web-toolkit+unsubscr...@googlegroups.com. To post to this group, send email to google-web-toolkit@googlegroups.com. Visit this group at http://groups.google.com/group/google-web-toolkit?hl=en. For more options, visit https://groups.google.com/groups/opt_out.
Re: GWT comet in push server mode?
Many projects have used comet to push data from server to client. This library seems stable although no changes in almost a year. Appengine's channel api uses comet, works really well, and is easy to implement. IMO, web sockets are more desirable to comet in terms of resource utilization. WS does not have the same Single Origin limitations and provides a more reliable connection. On Tue, Feb 12, 2013 at 5:04 AM, Maria Garcia maria.garcia.aguirrego...@gmail.com wrote: Hi, I have used comet library http://code.google.com/p/gwt-comet/wiki/GettingStarted to create a application. I would like to use comet to server pushes data to my client. Is it possible? Regards, -- You received this message because you are subscribed to the Google Groups Google Web Toolkit group. To unsubscribe from this group and stop receiving emails from it, send an email to google-web-toolkit+unsubscr...@googlegroups.com. To post to this group, send email to google-web-toolkit@googlegroups.com. Visit this group at http://groups.google.com/group/google-web-toolkit?hl=en. For more options, visit https://groups.google.com/groups/opt_out. -- -- A. Stevko === If everything seems under control, you're just not going fast enough. M. Andretti -- You received this message because you are subscribed to the Google Groups Google Web Toolkit group. To unsubscribe from this group and stop receiving emails from it, send an email to google-web-toolkit+unsubscr...@googlegroups.com. To post to this group, send email to google-web-toolkit@googlegroups.com. Visit this group at http://groups.google.com/group/google-web-toolkit?hl=en. For more options, visit https://groups.google.com/groups/opt_out.
gwt-comet issue with GWT 2.5
Hi All I know this is not a GWT direct issue, but I was not able to find a solution for the problem, so maybe someone out there already dealt with this problem. I'm using gwt-comet project and it has been working perfectly so far, but now that I'm upgrading to GWT 2.5 I'm getting an error ( http://code.google.com/p/gwt-comet/issues/detail?id=33). I need to know if there is a solution (a JAR available compiled with GWT 2.5) or if anyone suggest a different project so I can replace the gwt-comet. Thanks in advance, Aldo -- You received this message because you are subscribed to the Google Groups Google Web Toolkit group. To post to this group, send email to google-web-toolkit@googlegroups.com. To unsubscribe from this group, send email to google-web-toolkit+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-web-toolkit?hl=en.
Re: gwt-comet - CometException: EventSource error
Hi, here is additional information: The call failed on the server. See the tomcat log below. I also found somewhere that the version of gwt-comet relates to the GWT version. Magnus - Nov 19, 2012 7:30:31 AM org.apache.catalina.core.ApplicationContext log SEVERE: Exception while dispatching incoming RPC call com.google.gwt.user.server.rpc.UnexpectedException: Service method 'public abstract void cometchat.client.svc.ChatService.send(java.lang.String) throws cometchat.client.ChatException' threw an unexpected exception: java.lang.IllegalStateException: CometSession has been invalidated at com.google.gwt.user.server.rpc.RPC.encodeResponseForFailure(RPC.java:385) at com.google.gwt.user.server.rpc.RPC.invokeAndEncodeResponse(RPC.java:588) at com.google.gwt.user.server.rpc.RemoteServiceServlet.processCall(RemoteServiceServlet.java:208) at com.google.gwt.user.server.rpc.RemoteServiceServlet.processPost(RemoteServiceServlet.java:248) at com.google.gwt.user.server.rpc.AbstractRemoteServiceServlet.doPost(AbstractRemoteServiceServlet.java:62) at javax.servlet.http.HttpServlet.service(HttpServlet.java:637) at javax.servlet.http.HttpServlet.service(HttpServlet.java:717) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:852) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489) at java.lang.Thread.run(Thread.java:662) Caused by: java.lang.IllegalStateException: CometSession has been invalidated at net.zschech.gwt.comet.server.impl.CometSessionImpl.ensureValid(CometSessionImpl.java:65) at net.zschech.gwt.comet.server.impl.CometSessionImpl.enqueue(CometSessionImpl.java:77) at cometchat.server.ChatServiceImpl.send(ChatServiceImpl.java:127) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at com.google.gwt.user.server.rpc.RPC.invokeAndEncodeResponse(RPC.java:569) ... 17 more Nov 19, 2012 7:32:49 AM org.apache.catalina.core.ApplicationContext log SEVERE: Error sending heartbeat ClientAbortException: java.net.SocketException: Broken pipe at org.apache.catalina.connector.OutputBuffer.doFlush(OutputBuffer.java:319) at org.apache.catalina.connector.OutputBuffer.flush(OutputBuffer.java:288) at org.apache.catalina.connector.CoyoteOutputStream.flush(CoyoteOutputStream.java:98) at net.zschech.gwt.comet.server.deflate.DeflaterOutputStream.flush(DeflaterOutputStream.java:100) at sun.nio.cs.StreamEncoder.implFlush(StreamEncoder.java:278) at sun.nio.cs.StreamEncoder.flush(StreamEncoder.java:122) at java.io.OutputStreamWriter.flush(OutputStreamWriter.java:212) at net.zschech.gwt.comet.server.impl.CometServletResponseImpl.flush(CometServletResponseImpl.java:366) at net.zschech.gwt.comet.server.impl.CometServletResponseImpl.heartbeat(CometServletResponseImpl.java:345) at net.zschech.gwt.comet.server.impl.ManagedStreamCometServletResponseImpl.heartbeat(ManagedStreamCometServletResponseImpl.java:100) at net.zschech.gwt.comet.server.impl.BlockingAsyncServlet.suspend(BlockingAsyncServlet.java:92) at net.zschech.gwt.comet.server.impl.CometServletResponseImpl.suspend(CometServletResponseImpl.java:269) at net.zschech.gwt.comet.server.CometServlet.doCometImpl(CometServlet.java:157) at net.zschech.gwt.comet.server.CometServlet.doGet(CometServlet.java:108) at javax.servlet.http.HttpServlet.service(HttpServlet.java:617) at javax.servlet.http.HttpServlet.service(HttpServlet.java:717) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206
gwt-comet - CometException: EventSource error
Hello, I would like to use gwt-comet: http://code.google.com/p/gwt-comet/ To get started, I tested the chat application provided with on the project site: http://code.google.com/p/gwt-comet/wiki/ChatExample I also got the example running: It works fine within eclipse and with GWT development mode. Then, I deployed it as a war file to my tomcat 6 server, and I receive this error repeatedly within the chat window: error false net.zschech.gwt.comet.client.CometException: EventSource error Does anyone have an idea what could be the cause? How are your experiences with gwt-comet? Thanks Magnus -- You received this message because you are subscribed to the Google Groups Google Web Toolkit group. To view this discussion on the web visit https://groups.google.com/d/msg/google-web-toolkit/-/D-EFHGm8HLoJ. To post to this group, send email to google-web-toolkit@googlegroups.com. To unsubscribe from this group, send email to google-web-toolkit+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-web-toolkit?hl=en.
Errai Bus or GWT-comet
We are evaluating the Errai Bus and Gwt-comet for adding server push to our applications. Has anyone used any of the two? Can you provide your thoughts on the two libraries?. Greatly appreciate it. -- You received this message because you are subscribed to the Google Groups Google Web Toolkit group. To post to this group, send email to google-web-toolkit@googlegroups.com. To unsubscribe from this group, send email to google-web-toolkit+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-web-toolkit?hl=en.
GWT Comet Processor Implementation
Hi, I am trying to implement CometProcessor in GWT 1.6. I got a sample for the same from http://groups.google.com/group/Google-Web-Toolkit/browse_thread/thread/ee2f9207de953fc0d886f73f7dd17388?lnk=raot But still that implementations was for older versions of GWT. Does anyone got a sample for CometProcessor Implementation in GWT? --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups Google Web Toolkit group. To post to this group, send email to Google-Web-Toolkit@googlegroups.com To unsubscribe from this group, send email to google-web-toolkit+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/Google-Web-Toolkit?hl=en -~--~~~~--~~--~--~---
Re: GWT Comet Processor Implementation
The link you posted doesn't work for me, I don't know what CometProcessor is but if you just need a Comet implementaton for GWT you can try GWTEventService. On Jun 13, 5:29 am, Kousikraj kousik...@gmail.com wrote: Hi, I am trying to implement CometProcessor in GWT 1.6. I got a sample for the same from http://groups.google.com/group/Google-Web-Toolkit/browse_thread/threa... But still that implementations was for older versions of GWT. Does anyone got a sample for CometProcessor Implementation in GWT? --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups Google Web Toolkit group. To post to this group, send email to Google-Web-Toolkit@googlegroups.com To unsubscribe from this group, send email to google-web-toolkit+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/Google-Web-Toolkit?hl=en -~--~~~~--~~--~--~---
Re: GWT + comet?
I hate to say it but you've got me wondering now. I mean, it would be a whole lot easier to do considering you can see the source code of your competitor a lot easier these days... On Sep 7, 5:29 pm, Reinier Zwitserloot [EMAIL PROTECTED] wrote: Glad you liked the missive. I've saved a bookmark for future reference in case someone else comes in and asks (Comet usually comes up once a month or so). For game development: Just screw IE. There's no way to do halfway decent graphics on IE, period. Go flash, or tell people to switch to firefox/opera/safari/comet. All 3 non-IE browsers are trying to speed up javascript. Opera 9.5 has a fairly spiffy javascript engine already, and both firefox and webkit are on the verge of shipping custom very smart and very fast VMs for javascript (tracemonkey for firefox, and squirrelfish for safari). Then there's V8, which you can see at work today in Google Chrome. It looks like V8, Tracemonkey, and squirrelfish will all be roughly as fast as one another (can you say meep meep?) - should do wonders for attempts to write games in canvas. Which brings us back to IE. F!*k IE. There's future hope though: I believe apple has rescinded copyright/patent claims on canvas, or they ran out, so in theory nothing is stopping IE from implementing them now - though as I understand it, Microsoft never expressed interest in supporting them. Microsoft is part of the W3C and evidently they have not been able to use their considerable weight there to stop the latest news at W3C. W3C's own home-grown XHTML 2.0 effort has effectively been mothballed indefinitely, and instead HTML5 has been adopted (HTML5 started as something from the WHAT-WG, which is a much less officious entity compared to W3C, and consists of the developers of Opera, WebKit (Safari), and Gecko (Firefox/mozilla). - e.g. the anti-IE league, and the main reason stuff like canvas has seeded so quickly to the other non-IE browsers) HTML5 has been dollied up with some lip service to XHTML but make no mistake: Few really expected the W3C to 'fold' to the clearly superior HTML5 work in progress. HTML5 includes Canvas (seehttp://www.whatwg.org/specs/web-apps/current-work/multipage/the-canva... for proof). The question now becomes: Does Microsoft break even more from the W3C than they already have (remember, IE isn't exactly standards compliant). So far betas ofIE8indicate that Microsoft is seriously attempting to build a more compatible browser, so there's hope. Then again, armchair analysts (like myself ㋛) believe that Microsoft is still trying to prevent the web from becoming the host of virtually every computer app out there, in order to keep their own OS (Windows) in a safe market leader position. Microsoft's stranglehold on the web community by way of IE is one of the things holding web apps back, so there are plenty of pessimists who believe that the final version ofIE8will be a big disappointment. On Sep 7, 9:41 pm, markww [EMAIL PROTECTED] wrote: Thanks for the excellent response, that was very helpful. Everything makes sense, I was taking a look at Jetty and it seems easy to use for what I want to do. I had been writing my own java nio server for a class I was taking, it's cool to see how Jetty has taken advantage of the nio stuff to support 'comet'. From a game development point of view, this is great because we can wait for the server to send us data instead of constantly polling it. One thing that still seems to be missing is fast graphics support, to actually render dynamic game data. I was working with the gwt canvas intensively a few months ago, but was disappointed to find out that IE's support for it was just horrible. Firefox and Safari (and probably Chrome now) can do a decent job of rendering simple primitives fast in a canvas. In fact, my iPhone could render primitives faster than IE! I wonder if there is any development on this (providing a fast canvas for direct pixel manipulation) by the browsers. Right now it seems like the only way to do it is by using Flash. Anyway thanks again for all those answers, definitely got me in the right direction, Mark On Sep 7, 6:30 am, Reinier Zwitserloot [EMAIL PROTECTED] wrote: As you said, comet is a complex problem on the server side. On the client it's relatively straightforward. Some issues: 1) You either need an async webserver (such as something based on the fairly new java Simple, or the continuation support available in jetty), or you need an OS + VM combo which can handle tons of threads without a high overhead (the latest linux + the latest java 6 seems capable of this). Be especially careful if you've got a frontloader (such as Apache) that merely redirects to your actual java stuff. Apache, out of the box, will probably not use the new worked thread mechanism to communicate with the java server at the backend, and by default
Re: GWT + comet?
On 7 sep, 05:50, markww wrote: Is there any 'comet' support via GWT at the moment? I'm not completely up to speed with javascript / browser technologies, I believe comet was the practice of having the browser keep a connection open to the server so the server could push data to the browser whenever it wanted, instead of the client browser always polling for new data. I'm not sure where GWT would fit into that as it would require some logic server-side to work. Has there been any development with this, where can I start? Completing Reinier's wonderful overview: http://code.google.com/p/google-web-toolkit-incubator/wiki/ServerPushFAQ http://code.google.com/p/rocket-gwt/wiki/Comet --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups Google Web Toolkit group. To post to this group, send email to Google-Web-Toolkit@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/Google-Web-Toolkit?hl=en -~--~~~~--~~--~--~---
Re: GWT + comet?
Ok so after doing some reading it seems there are quite a few viable options on how to get started with comet. I can choose any setup I want for the backend, right now I'm leaning towards Jetty but it's hard to decide. There seem to be articles dating from 2007 / GWT 1.4 which give conflicting reports on the state of support Jetty and Tomcat offer: Go with Jetty: -easy to setup and supports continuations -should I go with version 6, or version 7 though? Version 6 seems to use continuations which are a way of imitating comet (bad explanation) but as I understand it, version 7 will have a new 'real' continuation system for 'servlet 3'? So which to choose? -can you debug your webapp using Jetty as the server, I thought GWT uses Tomcat by default? -need a GWT hack to get it to work: http://docs.codehaus.org/display/JETTY/GWT because GWT marked some class methods final which Jetty can't work with (v6) for RPC, don't know if that's different with v7. Go with Tomcat: -GWT uses this as the server for debugging? that's a plus. -Seems more difficult to configure to work with comet than Jetty, though most of the articles I find on this date to pre GWT 1.5 in 2007, not sure what the current state of support is. In terms of the GWT side of things, it seems like the chat example here: http://groups.google.com/group/gwtapps/files is a good one to use as a comet example. Though it is GWT 1.4, I don't know how much needs to be ported. Thanks for any comments, Mark On Sep 8, 6:23 am, Thomas Broyer [EMAIL PROTECTED] wrote: On 7 sep, 05:50, markww wrote: Is there any 'comet' support via GWT at the moment? I'm not completely up to speed with javascript / browser technologies, I believe comet was the practice of having the browser keep a connection open to the server so the server could push data to the browser whenever it wanted, instead of the client browser always polling for new data. I'm not sure where GWT would fit into that as it would require some logic server-side to work. Has there been any development with this, where can I start? Completing Reinier's wonderful overview:http://code.google.com/p/google-web-toolkit-incubator/wiki/ServerPushFAQhttp://code.google.com/p/rocket-gwt/wiki/Comet --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups Google Web Toolkit group. To post to this group, send email to Google-Web-Toolkit@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/Google-Web-Toolkit?hl=en -~--~~~~--~~--~--~---
Re: GWT + comet?
On Sep 8, 7:49 pm, markww [EMAIL PROTECTED] wrote: -can you debug your webapp using Jetty as the server, I thought GWT uses Tomcat by default? GWTShell embeds Tomcat, but you can use the -noserver mode and use whatever server software you want. You just lose the ability to debug both your client and server code at the same time (i.e. in one click; I suppose you can debug more than one app at the same time within e.g. Eclipse) --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups Google Web Toolkit group. To post to this group, send email to Google-Web-Toolkit@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/Google-Web-Toolkit?hl=en -~--~~~~--~~--~--~---
Re: GWT + comet?
As you said, comet is a complex problem on the server side. On the client it's relatively straightforward. Some issues: 1) You either need an async webserver (such as something based on the fairly new java Simple, or the continuation support available in jetty), or you need an OS + VM combo which can handle tons of threads without a high overhead (the latest linux + the latest java 6 seems capable of this). Be especially careful if you've got a frontloader (such as Apache) that merely redirects to your actual java stuff. Apache, out of the box, will probably not use the new worked thread mechanism to communicate with the java server at the backend, and by default apache will start serving up 'busy' pages if more than 50 simultaneous connections are already running. You get to 50 very quickly when using comet. If this is your setup, google around for how to implement apache+comet+java properly. Personally I just run jetty only, no apache. 2) The only safe way to do comet is to make a request from the client to the server, then the server returns NOTHING, not a single byte, it just waits, and then, once data is available, it sends it, and then closes the connection. In response, the client should open another connection and this whole song and dance number is repeated. The reason you can't just keep sending data across a single HTTP connection, is because the HTTP standard has no concept of 'flush'. A proxy or even the webclient itself (IE and Safari both do some limited caching, for example) will simply assume more will come very shortly, and never forward the data to the endpoint (your GWT app). In order to do this concept right, you need some sort of tracking number. For example, imagine an IRC (chat) client using comet. You could simply assign to each chat line in the chat room an index number, and upon first connect, tell the client the last chat line index number spoken. From here on out, comet can be done by letting the client request http://www.mychatserver.com/chats/line?idx=; + lastReceivedChatLineIdx++ - the server, upon receiving such a request, first checks if a line with that idx has already been said. If so, it is returned immediately (no comet). if NOT, it will not return an error, it will instead just wait and hold the connection open. Your servlet should register a listener of some sort with the central repository of chat messages, so it can wake up when the line with the given idx is actually spoken. You can't just ask for 'the next line' without a tracker ID of some sort, because in between receiving one line, processing it on the client, and opening another connection, a line might have been spoken. Without tracking you'd miss this line. 3) Because proxies, webservers, and web clients all have HTTP timeouts, and they are all different, you should manually close the connection after ~50 seconds. In our chat example, you'd send back something like: [NO CHAT] to indicate to the client that in the entire 50 second span, the chat line with idx '1234' never came up so far. In response, the client should re-open the connection with the exact same request (gimme line 1234). 4) For efficiency you may want to let the server respond with all relevant messages that have a tracker ID equal to or larger than the requested item. For example, in our chat app, if a client asks for message #1234, but on the server you already know that we're on message 1237 (a burst of rapid chats just recently happened, for example), then you should just send 1234, 1235, 1236, and 1237 in one go. You'll need a way to delimit each 'packet' of information in the response in this case. You could use JSON, for example. Or use a GWT- RPC call, though I don't know the specifics of making that work right with comet. 5) Web clients internally have a 2 connections limit. This means that, for any given full server name, if there are already 2 open connections, and a third thing is requested from this server, the client will queue up this request instead of sending it. Once one of those 2 open connections is closed, it will send it. This is perfectly reasonable when all requests are handled as fast as possible, but in comet, the whole point is that requests are NOT handled as fast as possible. If you have multiple comet elements on a single web page (Let's say, a 'live' stock ticker AND a chat box, each running a separate comet connection), then you're out of connections, and the act of requesting a simple image in response to a mouse over or some such never goes through! There are two solutions to this: A) run your non-AJAX calls off a different server. For example, serve up images from img.yourhost.com instead of just yourhost.com. You can't do this for your comet connections, because those usually use AJAX calls, and those must go to the same domain as the web page (Same Origin Policy, wikipedia that if you don't know what that is). This won't help you if you have 3 separate comety things going on, and it won't help
Re: GWT + comet?
Thanks for the excellent response, that was very helpful. Everything makes sense, I was taking a look at Jetty and it seems easy to use for what I want to do. I had been writing my own java nio server for a class I was taking, it's cool to see how Jetty has taken advantage of the nio stuff to support 'comet'. From a game development point of view, this is great because we can wait for the server to send us data instead of constantly polling it. One thing that still seems to be missing is fast graphics support, to actually render dynamic game data. I was working with the gwt canvas intensively a few months ago, but was disappointed to find out that IE's support for it was just horrible. Firefox and Safari (and probably Chrome now) can do a decent job of rendering simple primitives fast in a canvas. In fact, my iPhone could render primitives faster than IE! I wonder if there is any development on this (providing a fast canvas for direct pixel manipulation) by the browsers. Right now it seems like the only way to do it is by using Flash. Anyway thanks again for all those answers, definitely got me in the right direction, Mark On Sep 7, 6:30 am, Reinier Zwitserloot [EMAIL PROTECTED] wrote: As you said, comet is a complex problem on the server side. On the client it's relatively straightforward. Some issues: 1) You either need an async webserver (such as something based on the fairly new java Simple, or the continuation support available in jetty), or you need an OS + VM combo which can handle tons of threads without a high overhead (the latest linux + the latest java 6 seems capable of this). Be especially careful if you've got a frontloader (such as Apache) that merely redirects to your actual java stuff. Apache, out of the box, will probably not use the new worked thread mechanism to communicate with the java server at the backend, and by default apache will start serving up 'busy' pages if more than 50 simultaneous connections are already running. You get to 50 very quickly when using comet. If this is your setup, google around for how to implement apache+comet+java properly. Personally I just run jetty only, no apache. 2) The only safe way to do comet is to make a request from the client to the server, then the server returns NOTHING, not a single byte, it just waits, and then, once data is available, it sends it, and then closes the connection. In response, the client should open another connection and this whole song and dance number is repeated. The reason you can't just keep sending data across a single HTTP connection, is because the HTTP standard has no concept of 'flush'. A proxy or even the webclient itself (IE and Safari both do some limited caching, for example) will simply assume more will come very shortly, and never forward the data to the endpoint (your GWT app). In order to do this concept right, you need some sort of tracking number. For example, imagine an IRC (chat) client using comet. You could simply assign to each chat line in the chat room an index number, and upon first connect, tell the client the last chat line index number spoken. From here on out, comet can be done by letting the client requesthttp://www.mychatserver.com/chats/line?idx=; + lastReceivedChatLineIdx++ - the server, upon receiving such a request, first checks if a line with that idx has already been said. If so, it is returned immediately (no comet). if NOT, it will not return an error, it will instead just wait and hold the connection open. Your servlet should register a listener of some sort with the central repository of chat messages, so it can wake up when the line with the given idx is actually spoken. You can't just ask for 'the next line' without a tracker ID of some sort, because in between receiving one line, processing it on the client, and opening another connection, a line might have been spoken. Without tracking you'd miss this line. 3) Because proxies, webservers, and web clients all have HTTP timeouts, and they are all different, you should manually close the connection after ~50 seconds. In our chat example, you'd send back something like: [NO CHAT] to indicate to the client that in the entire 50 second span, the chat line with idx '1234' never came up so far. In response, the client should re-open the connection with the exact same request (gimme line 1234). 4) For efficiency you may want to let the server respond with all relevant messages that have a tracker ID equal to or larger than the requested item. For example, in our chat app, if a client asks for message #1234, but on the server you already know that we're on message 1237 (a burst of rapid chats just recently happened, for example), then you should just send 1234, 1235, 1236, and 1237 in one go. You'll need a way to delimit each 'packet' of information in the response in this case. You could use JSON, for example. Or use a GWT- RPC call, though I don't know the
Re: GWT + comet?
Glad you liked the missive. I've saved a bookmark for future reference in case someone else comes in and asks (Comet usually comes up once a month or so). For game development: Just screw IE. There's no way to do halfway decent graphics on IE, period. Go flash, or tell people to switch to firefox/opera/safari/comet. All 3 non-IE browsers are trying to speed up javascript. Opera 9.5 has a fairly spiffy javascript engine already, and both firefox and webkit are on the verge of shipping custom very smart and very fast VMs for javascript (tracemonkey for firefox, and squirrelfish for safari). Then there's V8, which you can see at work today in Google Chrome. It looks like V8, Tracemonkey, and squirrelfish will all be roughly as fast as one another (can you say meep meep?) - should do wonders for attempts to write games in canvas. Which brings us back to IE. F!*k IE. There's future hope though: I believe apple has rescinded copyright/patent claims on canvas, or they ran out, so in theory nothing is stopping IE from implementing them now - though as I understand it, Microsoft never expressed interest in supporting them. Microsoft is part of the W3C and evidently they have not been able to use their considerable weight there to stop the latest news at W3C. W3C's own home-grown XHTML 2.0 effort has effectively been mothballed indefinitely, and instead HTML5 has been adopted (HTML5 started as something from the WHAT-WG, which is a much less officious entity compared to W3C, and consists of the developers of Opera, WebKit (Safari), and Gecko (Firefox/mozilla). - e.g. the anti-IE league, and the main reason stuff like canvas has seeded so quickly to the other non-IE browsers) HTML5 has been dollied up with some lip service to XHTML but make no mistake: Few really expected the W3C to 'fold' to the clearly superior HTML5 work in progress. HTML5 includes Canvas (see http://www.whatwg.org/specs/web-apps/current-work/multipage/the-canvas.html for proof). The question now becomes: Does Microsoft break even more from the W3C than they already have (remember, IE isn't exactly standards compliant). So far betas of IE8 indicate that Microsoft is seriously attempting to build a more compatible browser, so there's hope. Then again, armchair analysts (like myself ㋛) believe that Microsoft is still trying to prevent the web from becoming the host of virtually every computer app out there, in order to keep their own OS (Windows) in a safe market leader position. Microsoft's stranglehold on the web community by way of IE is one of the things holding web apps back, so there are plenty of pessimists who believe that the final version of IE8 will be a big disappointment. On Sep 7, 9:41 pm, markww [EMAIL PROTECTED] wrote: Thanks for the excellent response, that was very helpful. Everything makes sense, I was taking a look at Jetty and it seems easy to use for what I want to do. I had been writing my own java nio server for a class I was taking, it's cool to see how Jetty has taken advantage of the nio stuff to support 'comet'. From a game development point of view, this is great because we can wait for the server to send us data instead of constantly polling it. One thing that still seems to be missing is fast graphics support, to actually render dynamic game data. I was working with the gwt canvas intensively a few months ago, but was disappointed to find out that IE's support for it was just horrible. Firefox and Safari (and probably Chrome now) can do a decent job of rendering simple primitives fast in a canvas. In fact, my iPhone could render primitives faster than IE! I wonder if there is any development on this (providing a fast canvas for direct pixel manipulation) by the browsers. Right now it seems like the only way to do it is by using Flash. Anyway thanks again for all those answers, definitely got me in the right direction, Mark On Sep 7, 6:30 am, Reinier Zwitserloot [EMAIL PROTECTED] wrote: As you said, comet is a complex problem on the server side. On the client it's relatively straightforward. Some issues: 1) You either need an async webserver (such as something based on the fairly new java Simple, or the continuation support available in jetty), or you need an OS + VM combo which can handle tons of threads without a high overhead (the latest linux + the latest java 6 seems capable of this). Be especially careful if you've got a frontloader (such as Apache) that merely redirects to your actual java stuff. Apache, out of the box, will probably not use the new worked thread mechanism to communicate with the java server at the backend, and by default apache will start serving up 'busy' pages if more than 50 simultaneous connections are already running. You get to 50 very quickly when using comet. If this is your setup, google around for how to implement apache+comet+java properly. Personally I just run jetty only, no apache. 2) The only safe way to do
GWT + comet?
Hi, Is there any 'comet' support via GWT at the moment? I'm not completely up to speed with javascript / browser technologies, I believe comet was the practice of having the browser keep a connection open to the server so the server could push data to the browser whenever it wanted, instead of the client browser always polling for new data. I'm not sure where GWT would fit into that as it would require some logic server-side to work. Has there been any development with this, where can I start? Thanks --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups Google Web Toolkit group. To post to this group, send email to Google-Web-Toolkit@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/Google-Web-Toolkit?hl=en -~--~~~~--~~--~--~---
