Update socket_setmulticastttl_ttl.md

dgram/socket_setmulticastttl_ttl.md

@@ -4,12 +4,9 @@ added: v0.3.8
 
 * `ttl` {number} Integer
 
-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.
-
-The argument passed to to `socket.setMulticastTTL()` is a number of hops
-between 0 and 255. The default on most systems is `1` but can vary.
+设置`IP_MULTICAST_TTL`套接字选项。
+一般来说，TTL表示"生存时间"。这里特指一个IP数据包传输时允许的最大跳步数，尤其是对多播传输。
+当IP数据包每向前经过一个路由或网关时，TTL值减1，若经过某个路由时，TTL值被减至0，便不再继续向前传输。
+
+传给 `socket.setMulticastTTL()` 的参数是一个范围为0-255的跳步数。大多数系统的默认值是 `1` ，但是可以变化。