Urg: Indicates to the receiver to do urgent processing as long as there is data to be consumed.

URG：向接收方表明一接收完数据就进行紧急处理。

You can specify which incoming TCP packets to scan and discard those that don't match the flags ack, FIN, PSH, RST, SYN, or URG.

可以指定应该扫描哪些到达的TCP数据包，丢弃不与ack、FIN、P SH、RST、syn或urg标志匹配的数据包。