远程 IP 系列的字符串表示形式。'IPv4' 或 'IPv6'。如果套接字被销毁(例如,如果客户端断开连接),则值可能是 undefined。
'IPv4'
'IPv6'
undefined
¥The string representation of the remote IP family. 'IPv4' or 'IPv6'. Value may be undefined if the socket is destroyed (for example, if the client disconnected).