tlsSocket.getEphemeralKeyInfo()
返回一个对象，表示客户端连接上 完全前向保密 中临时密钥交换的参数的类型、名称和大小。当密钥交换不是短暂的时，则它返回空对象。因为这仅在客户端套接字上受支持；如果在服务器套接字上调用，则返回 null。支持的类型是 'DH' 和 'ECDH'。name 属性仅在类型为 'ECDH' 时可用。
¥Returns an object representing the type, name, and size of parameter of
an ephemeral key exchange in perfect forward secrecy on a client
connection. It returns an empty object when the key exchange is not
ephemeral. As this is only supported on a client socket; null is returned
if called on a server socket. The supported types are 'DH' and 'ECDH'. The
name property is available only when type is 'ECDH'.
例如：{ type: 'ECDH', name: 'prime256v1', size: 256 }。
¥For example: { type: 'ECDH', name: 'prime256v1', size: 256 }.