[1] TCP Keepalive HOWTO (2007-05-04 22:26:59 +09:00 版) http://www.tldp.org/HOWTO/html_single/TCP-Keepalive-HOWTO/

[2] Issue 401142 - chromium - on android some requests take in the order of minutes before reporting an error - An open-source project to help move the web forward. - Google Project Hosting (2015-09-27 20:06:58 +09:00 版) https://code.google.com/p/chromium/issues/detail?id=401142

[3] curl - How To Use (2020-09-21T09:01:13.000Z, 2020-10-01T06:19:43.681Z) https://curl.haxx.se/docs/manpage.html#--keepalive-time