ほい
パケットキャプチャで適当に確認

POST http://egg.5ch.net/test/bbs.cgi HTTP/1.0
Connection: close
Content-Type: application/x-www-form-urlencoded
Content-Length: 112
Host: egg.5ch.net
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Referer: http://egg.5ch.net/software/
User-Agent: Monazilla/1.00 (JaneXeno/220528)
Cookie: yuki=akari

submit=%8F%91%82%AB%8D%9E%82%DE&FROM=&mail=sage&MESSAGE=%21chkBBx%3A&bbs=software&key=1654094589&time=1659491810