getpeername(2) -- Linux man page
NAMEgetpeername - get name of connected peer socket
DESCRIPTIONGetpeername 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 too small.
RETURN VALUEOn success, zero is returned. On error, -1 is returned, and errno is set appropriately.
- 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 the operation.
- The name parameter points to memory not in a valid part of the process address space.
CONFORMING TOSVr4, 4.4BSD (the getpeername function call first appeared in 4.2BSD).
NOTEThe 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).
SEE ALSOaccept(2), bind(2), getsockname(2)