getsockname - get socket name
getsockname(int s, struct sockaddr *name, socklen_t
getsockname() returns the locally bound address information
for a specified
Common uses of this function are as follows:
+o When bind(2) is called with a port number of 0 (indicating the kernel
should pick an ephemeral port) getsockname() is used to
kernel-assigned port number.
+o When a process calls bind(2) on a wildcard IP address,
is used to retrieve the local IP address for the connection.
+o When a function wishes to know the address family of a
getsockname() can be used.
getsockname() takes three parameters:
s contains the file descriptor for the socket to be looked
name points to a sockaddr structure which will hold the resulting address
information. Normal use requires one to use a structure
specific to the
protocol family in use, such as sockaddr_in (IPv4) or sockaddr_in6
(IPv6), cast to a (struct sockaddr *).
For greater portability (such as newer protocol families)
the new structure
sockaddr_storage exists. sockaddr_storage is large
enough to hold
any of the other sockaddr_* variants. On return, it should
be cast to
the correct sockaddr type, according to the current protocol
namelen indicates the amount of space pointed to by name, in
return, namelen is set to the actual size of the returned
If the address of the destination socket for a given socket
needed, the getpeername(2) function should be used instead.
If name does not point to enough space to hold the entire
the result will be truncated to namelen bytes.
On success, getsockname() returns a 0, and namelen is set to
size of the socket address returned in name. Otherwise,
errno is set,
and a value of -1 is returned.
If getsockname() fails, errno is set to one of the following:
[EBADF] The argument s is not a valid descriptor.
[ENOTSOCK] The argument s is a file, not a socket.
[ENOBUFS] 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.
accept(2), bind(2), getpeereid(2), getpeername(2), socket(2)
The getsockname() function call appeared in 4.2BSD.
Names bound to sockets in the UNIX domain are inaccessible;
returns a zero length name.
OpenBSD 3.6 July 17, 1999
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