Le 12 nov. 2011 à 04:41, Conrad Shultz a écrit : > On 11/11/11 6:39 PM, Vojtěch Meluzín wrote: >> Hi, >> >> I'm using BSD sockets for some internet access, it works fine. But if there >> is no connection available, it waits for say 30 seconds completely stopping >> the application. Is there a way to determine if there is actually an >> internet connection, so that I can check before using sockets? > > (This has been extensively discussed in the past in the context of iOS > network availability. Search the archives for more info.) > > The only reliable way to verify connectivity is to attempt a connection. > Checking for physical connectivity might speed up failure detection > (assuming you don't care about connections on the loopback interface), > but there are a host (no pun intended) of reasons that you still might > not be able to connect. > > However, there are other options. > > For one, since you are using BSD sockets (and I have to ask: are you > sure that a higher level API wouldn't accomplish what you need?), you > can use setsockopt() to control various timeouts. One of the Darwin or > networking lists might be of more assistance at this level of the > application. > > More worrying is your statement that the wait "completely [stops] the > application." Are you saying that you are blocking the main thread > while waiting on I/O? This is almost always a bad idea in a > user-interactive application. The BSD sockets API is thread-safe (when > accessed from a single thread), so you could spawn a separate network > thread. I believe there is also a non-blocking mode within the sockets > system, but people on the Darwin list would be more helpful here. > > If you are able to use higher level APIs, life becomes somewhat easier. > One level up, using CFNetwork, Apple has detailed documentation about > how to handle this issue > (http://developer.apple.com/library/mac/#documentation/Networking/Conceptual/CFNetwork/CFStreamTasks/CFStreamTasks.html#//apple_ref/doc/uid/TP30001132-CH6-SW19). >
And if you find that CFStream does not fit your need (to high level for your purpose), you can just wrap you BSD socket into a CFSocketRef, and schedule it on the current run loop. -- Jean-Daniel _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
