Follow these steps and you should be able to connect.
1. Open SDK Manager.exe, select the tool bar, click Android SDK Manager, under Force https://...sources to be fetched using http://... tick it, this is mainly to protect The protocol https is converted to normal http
2. Open the hosts file in C:/WINDOWS/system32/drivers/etc with notepad and
add the following lines to the end.
74.125.28.136 dl-ssl.google.com
74.125.28.136 dl.google.com
74.125.28.136 www.google.com
74.125.28.136 www.googlesource.com
74.125.28.136 android.googlesource.com
74.125.28.136 cache.pack.google
After saving .com , disable the network, re-enable it, and then open the sdk manager to try.
If it doesn't work, try the following IPs respectively.
74.125.237.1
74.125.203.190
74.125.203.136
74.125.28.136
173.194.67.93
3. Add a proxy server and try again!
