这适用于iOS 10.2及更低版本,但升级到10.3后,当模拟器尝试通过HTTPS连接到运行在localhost上的开发服务器时,Xcode控制台会输出以下错误：

NSURLSession/NSURLConnection HTTP load Failed (kcfStreamErrorDomainSSL,-9802)
[] nw_coretls_callback_handshake_message_block_invoke_3 tls_handshake_continue: [-9807]

打印出URLSessionDataTask返回的错误显示：

Error Domain=NSURLErrorDomain Code=-1200 "An SSL error has occurred and a secure connection to the server cannot be made." UserInfo={NSURLErrorFailingURLPeerTrustErrorKey=<SecTrustRef: 0x600000527080>,NSLocalizedRecoverySuggestion=Would you like to connect to the server anyway?,_kcfStreamErrorDomainKey=3,_kcfStreamErrorCodeKey=-9802,NSErrorPeerCertificateChainKey=(
    "<cert(0x7ff3e1867200) s: localhost i: localhost>"
),NSUnderlyingError=0x60800024e880 {Error Domain=kcfErrorDomainCFNetwork Code=-1200 "(null)" UserInfo={_kcfStreamPropertySSLClientCertificateState=0,kcfStreamPropertySSLPeerTrust=<SecTrustRef: 0x600000527080>,_kcfNetworkcfStreamSSLErrorOriginalValue=-9802,kcfStreamPropertySSLPeerCertificates=(
    "<cert(0x7ff3e1867200) s: localhost i: localhost>"
)}},NSLocalizedDescription=An SSL error has occurred and a secure connection to the server cannot be made.,NSErrorFailingURLKey=https://localhost:3000/v1/login,NSErrorFailingURLStringKey=https://localhost:3000/v1/login,NSErrorClientCertificateStateKey=0}

参考：Apple: Developer: Guides and Sample Code: Technical Note TN2232: HTTPS Server Trust Evaluation

要创建自签名SSL证书,我使用以下命令：

openssl genrsa -aes256 -passout pass:x -out server.pass.key 2048
openssl rsa -passin pass:x -in server.pass.key -out server.key
rm server.pass.key
openssl req -new -sha256 -key server.key -out server.csr -subj /CN=localhost
openssl x509 -req -sha512 -days 365 -in server.csr -signkey server.key -out server.crt

资料来源：GitHub – seviu/iOS-SSL-localhost