SyncManager incorrect error reporting

[matejm]

If there is no network and I try to sync wallet, I get connection error, which is correct. But if I connect my computer to the internet and sync again, same error is reported (sync manager probably doesn't check for network again).
Same problem happens if there is network connection and I sync my wallet. After I disconnect my computer and try to sync again I get Wallet downloading dialog. If cancel button is pressed, Online wallet is corrupted message is displayed, which is also incorrect.

[viddrobnic]

QNetworkAccessManager::networkAccessible sometimes returns that network is accessible, even though it is not. It has been partially fixed in c843cc9 by checking QNetworkReply::error and emitting NETWORK_ERROR signal when error is not 0.

In specific occasions that are quite common, QNetworkReply never finishes and therefore I can't check the error. To fix this, there should be a network timeout.

[matejm]

Tested this again.

If there is no network and ...

This is not a problem anymore.

Same problem happens ...

If network is disconnected and sync is started, then nothing is reported. You can stare into repeating animation for an infinite amount of time. If cancelled, nothing happens as is should. Also when syncing again, Network server is unreachable error is reported.

As @DzinVision said, solution could be network timeout.

[matejm]

It seems that this is an official Qt bug.

I think this issue could be closed as we are not going to implement network timeout by ourselves.

[zigapk]

As the issue suggests, we can implement our own timeout that destroys the socket after some time. Thoughts?