Linux man pages : getsockname (2)
GETSOCKNAME(2) Linux Programmer's Manual GETSOCKNAME(2)
getsockname - get socket name
int getsockname(int s, struct sockaddr *name, socklen_t *namelen);
Getsockname returns the current name for the specified socket. The
namelen parameter should be initialized to indicate the amount of space
pointed to by name. On return it contains the actual size of the name
returned (in bytes).
On success, zero is returned. On error, -1 is returned, and errno is
EBADF The argument s is not a valid descriptor.
The argument s is a file, not a socket.
Insufficient resources were available in the system to perform
EFAULT The name parameter points to memory not in a valid part of the
process address space.
SVr4, 4.4BSD (the getsockname function call appeared in 4.2BSD). SVr4
documents additional ENOMEM and ENOSR error codes.
The third argument of getsockname is in reality an `int *' (and this is
what BSD 4.* and libc4 and libc5 have). Some POSIX confusion resulted
in the present socklen_t. The draft standard has not been adopted yet,
but glibc2 already follows it and also has socklen_t. See also
BSD Man Page 1993-07-24 GETSOCKNAME(2)