INADDR_ANY，是个特殊IP地址 ，表示任务的IP地址，作为服务器端的时候经常要用到。对于它的解释，摘用下面一段英文（来自于：http://www.cs.cmu.edu/~srini/15-441/F01.full/www/assignments/P2/htmlsim_split/node18.html）：
When you wrote your simple FTP server in project 1, you probably bound your listening socket to the special IP address INADDR_ANY. This allowed your program to work without knowing the IP address of the machine it was running on, or, in the case of a machine with multiple network interfaces, it allowed your server to receive packets destined to any of the interfaces. In reality, the semantics of INADDR_ANY are more complex and involved.
In the simulator, INADDR_ANY has the following semantics: When receiving, a socket bound to this address receives packets from all interfaces. For example, suppose that a host has interfaces 0, 1 and 2. If a UDP socket on this host is bound using INADDR_ANY and udp port 8000, then the socket will receive all packets for port 8000 that arrive on interfaces 0, 1, or 2. If a second socket attempts to Bind to port 8000 on interface 1, the Bind will fail since the first socket already “owns” that port/interface.
When sending, a socket bound with INADDR_ANY binds to the default IP address, which is that of the lowest-numbered interface.
