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    <p>If you're sending information using the TCP/IP protocol to apple you have to be receiving acknowledgements. However you stated: </p> <blockquote> <p>Apple doesn't return any acknowledgement whatsoever</p> </blockquote> <p>What do you mean by this? TCP/IP guarantees delivery therefore receiver MUST acknowledge receipt. It does not guarantee when the delivery will take place, however.</p> <p>If you send notification to Apple and you break your connection before receiving the ACK there is no way to tell whether you were successful or not so you simply must send it again. If pushing the same information twice is a problem or not handled properly by the device then there is a problem. The solution is to fix the device handling of the duplicate push notification: there's nothing you can do on the pushing side.</p> <p>@Comment Clarification/Question</p> <p>Ok. The first part of what you understand is your answer to the second part. Only the packets that have received ACKS have been sent and received properly. I'm sure we could think of some very complicated scheme of keeping track of each individual packet ourselves, but TCP is suppose to abstract this layer away and handle it for you. On your end you simply have to deal with the multitude of failures that could occur (in Java if any of these occur an exception is raised). If there is no exception the data you just tried to send is sent guaranteed by the TCP/IP protocol.</p> <p>Is there a situation where data is seemingly "sent" but not guaranteed to be received where no exception is raised? The answer should be no.</p> <p>@Examples</p> <p>Nice examples, this clarifies things quite a bit. I would have thought an error would be thrown. In the example posted an error is thrown on the second write, but not the first. This is interesting behavior... and I wasn't able to find much information explaining why it behaves like this. It does however explain why we must develop our own application level protocols to verify delivery.</p> <p>Looks like you are correct that without a protocol for confirmation their is no guarantee the Apple device will receive the notification. Apple also only queue's the last message. Looking a little bit at the service I was able to determine this service is more for convenience for the customer, but cannot be used to guarantee service and must be combined with other methods. I read this from the following source.</p> <p><a href="http://blog.boxedice.com/2009/07/10/how-to-build-an-apple-push-notification-provider-server-tutorial/" rel="nofollow noreferrer">http://blog.boxedice.com/2009/07/10/how-to-build-an-apple-push-notification-provider-server-tutorial/</a></p> <p>Seems like the answer is no on whether or not you can tell for sure. You may be able to use a packet sniffer like Wireshark to tell if it was sent, but this still won't guarantee it was received and sent to the device due to the nature of the service.</p>
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    1. POJava Sockets and Dropped Connections
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    1. USDerek Litz
    1. USDerek Litz
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    1. COI mean that Apple doesn't return any specific protocol acknowledgement beyond TCP ACK. I also don't know how I can tell which packets were sent properly and which ones weren't.
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    2. COThanks for the update. I realize I should have focused the question on TCP with the examples, rather than discuss Apple services. I think I'll give up for dropped connection detection support for now.
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