GETSOCKNAME(2) BSD System Calls Manual GETSOCKNAME(2)
getsockname -- get socket name
Standard C Library (libc, -lc)
getsockname(int s, struct sockaddr * restrict name, socklen_t * restrict namelen);
getsockname() returns the locally bound address information for a specified socket.
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 retrieve the kernel-assigned port number.
o When a process calls bind(2) on a wildcard IP address, getsockname() is used to retrieve
the local IP address for the connection.
o When a function wishes to know the address family of a socket, getsockname() can be
getsockname() takes three parameters:
s, Contains the file descriptor for the socket to be looked up.
name points to a sockaddr structure which will hold the resulting address information. Nor-
mal 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 bytes. Upon return, namelen is
set to the actual size of the returned address information.
If the address of the destination socket for a given socket connection is needed, the
getpeername(2) function should be used instead.
If name does not point to enough space to hold the entire socket address, the result will be
truncated to namelen bytes.
On success, getsockname() returns a 0, and namelen is set to the actual size of the socket
address returned in name. Otherwise, errno is set, and a value of -1 is returned.
The call succeeds unless:
[EBADF] The argument s is not a valid descriptor.
[ENOTSOCK] The argument s is a file, not a socket.
[EINVAL] The socket has been shut down.
[ENOBUFS] Insufficient resources were available in the system to perform the opera-
[EFAULT] The name parameter points to memory not in a valid part of the process
The getsockname() function call appeared in 4.2BSD.
Names bound to sockets in the UNIX domain are inaccessible; getsockname() returns a zero
BSD August 11, 2002 BSD