Address families define different styles of addressing. All hosts in a given address family understand and use the same scheme for addressing socket endpoints. TCP/IP supports addressing families AF_INET and AF_INET6. See Introducing TCP/IP concepts: Socket libraries to determine which APIs support the AF_INET or both the AF_INET and AF_INET6 address families. The AF_INET domain defines addressing for the IPv4 internet domain. The AF_INET6 domain defines addressing for the IPv6 internet domain.