Programming with sockets

Related functions

The following macros and socket functions provide the additional functionality required to write ``IPv6 ready'' applications.

The IN6_IS_ADDR_V4MAPPED macro, described on the inet(S) manual page, can be used to determine whether an IPv6 address is an IPv4-mapped address.
gethostbyname2(S) retrieves a network host entry via its name and address family.
getaddrinfo(S) returns address information related to a specified service location.
getnameinfo(S) returns the text strings associated with the supplied IP address and port number.
inet_pton(S) converts the specified address in text form to its binary equivalent.
inet_ntop(S) converts the specified binary address into its text equivalent suitable for presentation.

getaddrinfo and getnameinfo can both be used to retrieve information related to IPv4 and IPv6 addresses. inet_pton and inet_ntop can both convert IPv4 and IPv6 addresses. This means that in ``IPv6 ready'' applications, you do not need to use either inet_addr or inet_ntoa.

In addition to the new functions listed above, the following sockets functions have been modified.

bind(S)
connect(S)
sendmsg(S)
sendto(S)
accept(S)
recvfrom(S)
recvmsg(S)
getpeername(S)
getsockname(S)

No change in the syntax of these functions is necessary when using them for IPv6, as all addresses are referenced by ``opaque'' address pointers. The only difference when using these functions is that you must cast sockaddr_in6 to struct sockaddr* when using any of these functions except sendmsg and recvmsg. When you use these functions, set the structure member msghdr.msg_name to point to your sockaddr_in6 structure and store the length of the structure in msghdr.msg_namelen.