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 addr
. The addrlen
argument should be initialized to indicate the amount of space pointed to by
. 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
will return a value greater than was supplied to the
On success, zero is returned. On error, -1 is returned, and errno
- The argument sockfd is not a valid descriptor.
- The addr argument points to memory not in a valid part of the
process address space.
- addrlen is invalid (e.g., is negative).
- Insufficient resources were available in the system to perform the
- The socket is not connected.
- The argument sockfd is a file, not a socket.
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 4.x BSD and libc4 and libc5 have). Some POSIX confusion
resulted in the present socklen_t
, also used by glibc. See also
For stream sockets, once a connect(2)
has been performed, either socket
can call getpeername
() to obtain the address of the peer socket. On the
other hand, datagram sockets are connectionless. Calling connect(2)
a datagram socket merely sets the peer address for outgoing datagrams sent
. The caller of connect(2)
() to obtain the peer address that it earlier set for
the socket. However, the peer socket is unaware of this information, and
() on the peer socket will return no useful
information (unless a connect(2)
call was also executed on the peer).
Note also that the receiver of a datagram can obtain the address of the sender
when using recvfrom(2)
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