Well, there is a "nasty" but effective way to do that, although please note I am against it unless all else has failed and you must do it. It simply involves adding a dummy socket to one or more of the fd_sets, and triggering it when you want the select call to return. The ugly trigger is closing the socket. This could involve several problems but has worked for me before (use the read_fds for this). A more subtle trigger is a read or write to the socket. You should define a DATAGRAM socket, write a byte when you want select to return, and don't forget to consume this byte (using recv) when select actually returns.
HTH, Yoav. On 11/01/10 16:24 PM, Nicolas Pinault wrote: > > > Yoav Nissim a écrit : >> Simon, >> Is the half duplex limitation only a socket implementation issue? >> other than the missing locks, what else is missing? using the netconn >> API seems to result in the same problem. >> Isn't the TCPIP thread performing operations one at a time anyway? >> >> Nicolas, >> I'm sorry. I tried thinking about this for a while but the only way I >> could produce any helpful code here is if I throw myself into >> actually coding and testing it... my boss would not like that I >> imagine :) > Ok. I understand. No problem. >> Are you working with existing vnc server code that uses two threads, >> or are you writing the code yourself? > My code is based on a code I have found in eCos svn tree. The original > code uses 2 threads. One for receiving commands from client and one > for sending screen content. > >> If you have existing code, maybe you should try serializing the send >> and receive operations with a separate thread using select as I've >> suggested earlier. > I have modified my code to use only one thread. The result is > catastrophic. It works worse than ever. When trying to transmit, > select() terminates with a timeout (1sec) >> If you are writing your own code, could you clarify why a single >> thread (not the main) using select and doing all Rx and Tx would not >> work? > select() blocks until data are received or timeout occurs. > The system screen is updated by another thread. When the screen has > been updated, screen content must be sent to the client. > How do you go out of select() if you don't use timeout ? > > Nicolas >> Yoav. >> >> >> On 11/01/10 11:33 AM, Nicolas Pinault wrote: >>> Simon, >>> >>> Simon Goldschmidt a écrit : >>>>> 2. Keep Rx and Tx threads locked and waiting on a select running in >>>>> another thread (in essence adding the locking mechanism that lwIP >>>>> does >>>>> not support) >>>>> >>>> >>>> The idea is good, but it's not what lwIP doesn't support, since you >>>> don't get full duplex but mutual exclusion for read & write. Full >>>> duplex would allow simultaneously sending and receiving on the >>>> wire. However, that's the best you can get, currently, when using >>>> sockets. >>>> >>>> >>> My problem is not to simultaneously receive and transmit data. >>> My problem is that I have an application that receives data and >>> transmit data asynchronously. >>> My application is a vnc server. >>> Vnc server receives data from client when, for example, the user >>> moves the mouse or hits keys. >>> Vnc server sends screen content to client when needed. >>> The client can request the server to force send screen content. In >>> this case, no problem. >>> But vnc server can also need to send screen content while nothing is >>> received. >>> Two threads are ideal in this situation. One for receiving commands >>> and one for sending screen content. >>> >>> I can't see any other solution than using select with a short timeout. >>> >>> Nicolas >>> >>>> Simon >>>> >>> >>> >>> _______________________________________________ >>> lwip-users mailing list >>> [email protected] >>> http://lists.nongnu.org/mailman/listinfo/lwip-users >> >> -- >> Yoav Nissim >> Software Engineer, Software Tools Division >> Jungo Software Technologies >> Email: [email protected] >> Web: http://www.jungo.com >> Phone: +972-74-7212138 >> Fax: +972-74-7212122 >> Mobile: +972-54-2271315 >> ------------------------------------------------------------------------ >> >> _______________________________________________ >> lwip-users mailing list >> [email protected] >> http://lists.nongnu.org/mailman/listinfo/lwip-users > > > _______________________________________________ > lwip-users mailing list > [email protected] > http://lists.nongnu.org/mailman/listinfo/lwip-users -- Yoav Nissim Software Engineer, Software Tools Division Jungo Software Technologies Email: [email protected] Web: http://www.jungo.com Phone: +972-74-7212138 Fax: +972-74-7212122 Mobile: +972-54-2271315
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