Qt5.5以来对Network的改进（包括对SSL的功能支持，HTTP的重定向等等）

Qt Network

• New SSL back-end for iOS and OS X based on Secure Transport. Note that in Qt 5.6 this will become the default SSL: back-end on these platforms.
• Support for libproxy
• Support for TLS PSK ciphersuites
• Support for elliptic curve certificates
• Ability to select specific curves when using elliptic curve ciphersuites.

http://wiki.qt.io/New_Features_in_Qt_5.5

Qt Network

• Added QHostAddress::isMulticast()
• Support HTTP redirection in QNetworkAccessManager

http://wiki.qt.io/New_Features_in_Qt_5.6

Qt Network

• Support for TLS PSK ciphersuites on server side
• Support for configurable diffie hellman parameters
• Support for HTTP/2 in Network Access Manager

http://wiki.qt.io/New_Features_in_Qt_5.8

Qt Network

• Added HSTS support (HTTP Strict Transport Security) to QNetworkAccessManager
• Added redirects policy to QNetworkAccessManager (ManulRedirectsPolicy, NoLessSafeRedirectsPolicy, SameOriginRedirectsPolicy, UserVerifiedRedirectsPolicy)

http://wiki.qt.io/New_Features_in_Qt_5.9