After using yum update to keep all my software up-to-date, I found the ocserv cannot be connected. The TLS connection can be successfully established but it return nothing. I've checked the history of my updating and only http-parser was been upgraded to 2.7.1 which made this problem occur. So I decided to use an older version like 2.0 and the problem was solved. My OS: CentOS 7.3.1611 ===================================== Mail?from?Thomas?Lewis?(???) Tel:?(+86)?13126413113 E-mail:?thomaslewis at 0xAA55.me E-mail?(Encrypted):?thomaslewis at secure.0xAA55.me =====================================