The SOCKADDR structure is used to store an Internet Protocol (IP) address for a machine participating in a Windows Sockets communication.
The Microsoft TCP/IP Sockets Developer's Kit only supports the Internet address domains. To actually fill in values for each part of an address, you use the SOCKADDR_IN data structure, which is specifically for this address format. The SOCKADDR and the SOCKADDR_IN data structures are the same size. You simply cast to switch between the two structure types.