On 04/10/2013 22:49, Konstantin Preißer wrote: > Hi Mark, > > while I was developing and experimenting with a WebSocket application (that I > think could be added to Tomcat 8's WebSocket examples), I think I found some > more possible issues with the Websocket handling. One of these can be seen > with the Snake example. > > > A) For NIO and APR connector: > It seems that when a client establishes a Websocket connection and then stops > to read data from it (but doesn't close the connection, so that writing data > to the underlying TCP connection will be blocked), and then after some time > continues to read data from the Websocket connection, then Tomcat seems not > to be able to read data from that client any more (and doesn't notice when > the connection has been closed), but it can still read from it.
I think you have written read when you meant write somewhere in the previous sentence. > To reproduce: > 1) Start Tomcat (current trunk) on Windows 64-bit with Java7 64-bit and > either NIO or APR connector. > 2) Open two instances of Firefox (that may or may not be on the same machine) > and open the snake example. On both instances, press up or down key so that > both snakes begin moving. > 3) Suspend one of the two Firefox processes (say Firefox B). This can be done > with "Process Explorer" [1] tool by right-clicking on the firefox.exe entry > and select "Suspend". You can see that Firefox B does not respond any more, > but on Firefox A the snakes continue to move. > 4) After some time, you can see that on Firefox A the snakes suddenly stop > moving. This is correct because the current code uses RemoteEndpoint.Basic > that may block on write() methods. > 5) Now resume Firefox B with Process Explorer. You can see that on both > Firefoxes the snakes will continue to move. This means that both Firefoxes > are able to receive data from the Websocket connection. > 6) When you try to change the direction of the snake in Firefox A, everything > works. However on Firefox B, the snake will not change its direction. This > means that while Tomcat continues to send data to this Websocket connection, > it cannot receive from it any more. > 7) If you close Firefox B, then the corresponding snake will not disappear > (so it seems Tomcat doesn't notice that the connection closed). It would be worth taking a look with something like Wireshark to see if the data is being sent to Tomcat. > B) For BIO connector: > I noticed that on Tomcat with BIO connector, when using a > RemoteEndpoint.Async to asynchronously send data over the WebSocket > connection, sendText(String, SendHandler) (or similar methods) will block if > the Remote endpoint does not read data from the connection, whereas for NIO > and APR connector this method will always return immediately. > Is it intended that for the BIO connector those methods are blocking? As the > javadoc says, "Initiates the asynchronous transmission of a text message. > This method returns before the message is transmitted.", I would have > expected that e.g. another Thread is used to write in blocking mode, so that > the sendText() method can return immediately. You can't do non-blocking IO with the BIO connector. All communication with BIO is blocking. This is working as designed. Mark --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@tomcat.apache.org For additional commands, e-mail: dev-h...@tomcat.apache.org
