socket.setMulticastTTL(ttl)

• ttl <integer>

设置 IP_MULTICAST_TTL 套接字选项。虽然 TTL 通常代表 "生存时间"，但在此上下文中，它指定了允许数据包通过的 IP 跃点数，特别是对于多播流量。转发数据包的每个路由或网关都会递减 TTL。如果 TTL 被路由递减为 0，则不会转发。

¥Sets the IP_MULTICAST_TTL socket option. While TTL generally stands for "Time to Live", in this context it specifies the number of IP hops that a packet is allowed to travel through, specifically for multicast traffic. Each router or gateway that forwards a packet decrements the TTL. If the TTL is decremented to 0 by a router, it will not be forwarded.

ttl 参数可以是 0 到 255 之间。大多数系统上的默认值为 1。

¥The ttl argument may be between 0 and 255. The default on most systems is 1.

如果在未绑定的套接字上调用此方法将抛出 EBADF。

¥This method throws EBADF if called on an unbound socket.