Thank you very much for your help.
It takes some time for me (newbie) to figer out how it works and were are my problems. Under Win10 my example always crash. Suppose there are security limitation due Win10. Under Linux i got it to run.
First question is: Why does the Browser only show my HTTP-Code as plain text?
Second question is: Exist the query "conn->content" like in old Mongoose V5.4?
Sorry for me badly network knowlidge.