getpeername() returns the name of the peer connected to socket
s. One common use occurs when a process inherits an open socket, such as TCP servers forked from
inetd(8). In this scenario,
getpeername() is used to determine the connecting client's IP address.
getpeername() takes three parameters:
s contains the file descriptor of the socket whose peer should be looked up.
name points to a
sockaddr structure that will hold the address information for the connected peer. Normal use requires one to use a structure specific to the protocol family in use, such as
sockaddr_in (IPv4) or
sockaddr_in6 (IPv6), cast to a (struct sockaddr *).
For greater portability, especially with the newer protocol families, the new
struct sockaddr_storage should be used.
sockaddr_storage is large enough to hold any of the other sockaddr_* variants. On return, it can be cast to the correct sockaddr type, based on the protocol family contained in its ss_family field.
namelen indicates the amount of space pointed to by
name, in bytes.
If address information for the local end of the socket is required, the
getsockname(2) function should be used instead.
If
name does not point to enough space to hold the entire socket address, the result will be truncated to
namelen bytes.