Linux man pages : getpeername (2)
GETPEERNAME(2) Linux Programmer's Manual GETPEERNAME(2)
getpeername - get name of connected peer socket
int getpeername(int s, struct sockaddr *name, socklen_t *namelen);
Getpeername returns the name of the peer connected to socket s. 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). The name is truncated if the buffer provided is
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.
The socket is not connected.
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 getpeername function call first appeared in 4.2BSD).
The third argument of getpeername 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
accept(2), bind(2), getsockname(2)
BSD Man Page 1993-07-30 GETPEERNAME(2)