Section: Linux Programmer's Manual (2)
getpeername - get name of connected peer socket
int getpeername(int sockfd, struct sockaddr *addr, socklen_t *addrlen);
returns the address of the peer connected to the socket
in the buffer pointed to by
argument should be initialized to indicate the amount of space pointed to
On return it contains the actual size of the name returned (in bytes).
The name is truncated if the buffer provided is too small.
The returned address is truncated if the buffer provided is too small;
in this case,
will return a value greater than was supplied to the call.
On success, zero is returned.
On error, -1 is returned, and
is set appropriately.
is not a valid file descriptor.
argument points to memory not in a valid part of the
process address space.
is invalid (e.g., is negative).
Insufficient resources were available in the system
to perform the operation.
The socket is not connected.
The file descriptor
does not refer to a socket.
POSIX.1-2001, POSIX.1-2008, SVr4, 4.4BSD
first appeared in 4.2BSD).
For background on the
For stream sockets, once a
has been performed, either socket can call
to obtain the address of the peer socket.
On the other hand, datagram sockets are connectionless.
on a datagram socket merely sets the peer address for outgoing
datagrams sent with
The caller of
to obtain the peer address that it earlier set for the socket.
However, the peer socket is unaware of this information, and calling
on the peer socket will return no useful information (unless a
call was also executed on the peer).
Note also that the receiver of a datagram can obtain
the address of the sender when using
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