I've update iOS devices to 8.0 and now need to update xCode, but keep getting "unknown error -50" leaving me with a non-working internet connection - the only fix seems to be reboot of both iMac and router - any ideas?

Question

Having updated all my iOS devices to iOS 8.0 I now need to update xCode to match. I've tried several times, and on each occasion have received an "unknown error -50" message after getting about 500Mb. After this my internet connection appears to be fully occupied, and the only fix appears to be a reboot of both the iMac (2.5GHx Core i5, 4Gb RAMm OS X 10.9.5) and the router (Netgear DG834 v5, firmware 1.6.01.34) At first I thought that the error had not stopped the download, but after waiting for 30 minutes the connection was still unresponsive, though traffic was indicated as passing through but the router status page, and no additional content had been added to the download. Anyone else having a similar problem and different ideas as to fixing it?

Answer 1

Please read this whole message before doing anything.
This procedure is a diagnostic test. It’s unlikely to solve your problem. Don’t be disappointed when you find that nothing has changed after you complete it.
The purpose of the test is to determine whether the problem is caused by third-party software that loads automatically at startup or login, by a peripheral device, by a font conflict, or by corruption of the file system or of certain system caches.
Disconnect all wired peripherals except those needed for the test, and remove all aftermarket expansion cards, if applicable. Start up in safe mode and log in to the account with the problem. You must hold down the shift key twice: once when you turn on the computer, and again when you log in.
Note: If FileVault is enabled, or if a firmware password is set, or if the startup volume is a software RAID, you can’t do this. Ask for further instructions.
Safe mode is much slower to start up and run than normal, with limited graphics performance, and some things won’t work at all, including sound output and Wi-Fi on certain models. The next normal startup may also be somewhat slow.
The login screen appears even if you usually login automatically. You must know your login password in order to log in. If you’ve forgotten the password, you will need to reset it before you begin.
Test while in safe mode. Same problem?
After testing, restart as usual (not in safe mode) and verify that you still have the problem. Post the results of the test.