遇到的问题：
GCDWebServer不支持长链接，只要App退到后台，connect自动就stop，网页请求无法获得响应。
解决办法：
1）开启支持后台模式：将GCDWebServer.m中的GCDWebServerOption_AutomaticallySuspendInBackground设置为NO；
修改為：
_suspendInBackground = [_GetOption(_options, GCDWebServerOption_AutomaticallySuspendInBackground, @NO) boolValue];
2）打开Background Modes；
結果還是不行。
修改為 @NO 的 xcode console log:
[ERROR] Failed accepting IPv4 socket: Bad file descriptor (9) [DEBUG] Did open connection on socket 6 [DEBUG] Connection received 363 bytes on socket 6 [DEBUG] Connection on socket 6 preflighting request "GET /" with 363 bytes body [DEBUG] Connection on socket 6 processing request "GET /" with 363 bytes body [DEBUG] Did connect [DEBUG] Did start background task [DEBUG] Connection sent 182 bytes on socket 6 [ERROR] Error while writing to socket 6: Broken pipe (32) [DEBUG] Did close connection on socket 6 [VERBOSE] [192.168.31.237:8080] 192.168.31.237:56991 200 "GET /" (363 | 182) [DEBUG] Did disconnect [DEBUG] Did end background task
修改為 @YES 的 console log 一切換到背景，web server網路就斷了:
[DEBUG] Did open IPv4 listening socket 4 [DEBUG] Did open IPv6 listening socket 5 [INFO] GCDWebServer started on port 8080 and reachable at http://192.168.31.237:8080/ 2018-03-19 17:09:23.227 TkWebServer[3414:1442070] Visit http://192.168.31.237:8080/ in your web browser [DEBUG] Did enter background [DEBUG] Did close IPv6 listening socket 5 [DEBUG] Did close IPv4 listening socket 4 [INFO] GCDWebServer stopped
