argument has the same meaning as for socket.listen(). flags is a bitmask of AI_* flags to getaddrinfo, like socket.AI_PASSIVE | socket.AI_NUMERICHOST. reuse_port option sets SO_REUSEPORT option for every socket can be used to pass additional flags to getaddrinfo. • tornado.netutil.bind_sockets no longer sets AI_ADDRCONFIG; this will cause it to bind to both ipv4 and ipv6 more often than before. • tornado.netutil HTTPServer can now be run on a unix socket as well as TCP. • Fixed exception at startup when socket.AI_ADDRCONFIG is not available, as on Windows XP IOLoop and IOStream • IOStream performance has been

socket.listen]. flags is a bitmask of AI_* flags to getaddrinfo [https://docs.python.org/3/library/socket.html#socket.getaddrinfo], like socket.AI_PASSIVE | socket.AI_NUMERICHOST. reuse_port option sets that can be used to pass additional flags to getaddrinfo. tornado.netutil.bind_sockets no longer sets AI_ADDRCONFIG; this will cause it to bind to both ipv4 and ipv6 more often than before. tornado.netutil HTTPServer can now be run on a unix socket as well as TCP. Fixed exception at startup when socket.AI_ADDRCONFIG is not available, as on Windows XP IOLoop and IOStream IOStream performance has been improved