http://tools.ietf.org/html/rfc6066#section-3 defines Server Name Indication and says «The hostname is represented as a byte string using ASCII encoding without a trailing dot... Literal IPv4 and IPv6 addresses are not permitted in "HostName"». I take that to mean a dotted-quad ASCII string isn't allowed, perhaps to avoid the ambiguity of it and the destination IP address differing. The alternative is it means a 32-bit IPv4 address cannot be given, but that's already ruled out by "ASCII encoding".
A tls.Dial("tcp", "3.1.4.1:5", ...) passes "3.1.4.1" in the TLS's ClientHello.
http://tools.ietf.org/html/rfc6066#section-3 defines Server Name Indication and says «The hostname is represented as a byte string using ASCII encoding without a trailing dot... Literal IPv4 and IPv6 addresses are not permitted in "HostName"». I take that to mean a dotted-quad ASCII string isn't allowed, perhaps to avoid the ambiguity of it and the destination IP address differing. The alternative is it means a 32-bit IPv4 address cannot be given, but that's already ruled out by "ASCII encoding".
A tls.Dial("tcp", "3.1.4.1:5", ...) passes "3.1.4.1" in the TLS's ClientHello.