How to run the HTTP request without using CURL

busybox has wget but this limited and unsuitable for posting.
You can combine busybox with netcat (or nc) for achieving the result. You only need to download netcat binaries for your platform. And here we go:

POST_PATH="/login.cgi"
HOST=199.188.1.99
BODY="Put here HTML body...."
BODY_LEN=$( echo -n "${BODY}" | wc -c )
echo -ne "POST ${POST_PATH} HTTP/1.0\r\nHost: ${HOST}\r\nContent-Type: application/x-www-form-urlencoded\r\nContent-Length: ${BODY_LEN}\r\n\r\n${BODY}" | \
  nc -i 3 ${HOST} 80

Based on Sending HTTP POST request with netcat post.