Copyright (c) 1983, 1991, 1993
The Regents of the University of California. All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
3. Neither the name of the University nor the names of its contributors
may be used to endorse or promote products derived from this software
without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.
@(#)getsockname.2 8.1 (Berkeley) 6/4/93
.Dd July 30, 2016 .Dt GETSOCKNAME 2 .Os .Sh NAME .Nm getsockname .Nd get socket name .Sh LIBRARY .Lb libc .Sh SYNOPSIS n sys/socket.h .Ft int .Fn getsockname "int s" "struct sockaddr * restrict name" "socklen_t * restrict namelen" .Sh DESCRIPTION .Fn getsockname returns the locally bound address information for a specified socket.
p Common uses of this function are as follows: l -bullet t When .Xr bind 2 is called with a port number of 0 (indicating the kernel should pick an ephemeral port) .Fn getsockname is used to retrieve the kernel-assigned port number. t When a process calls .Xr bind 2 on a wildcard IP address, .Fn getsockname is used to retrieve the local IP address for the connection. t When a function wishes to know the address family of a socket, .Fn getsockname can be used. .El
p .Fn getsockname takes three parameters:
p .Fa s , Contains the file descriptor for the socket to be looked up.
p .Fa name points to a .Li 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 .Li sockaddr_in (IPv4) or .Li sockaddr_in6 (IPv6), cast to a (struct sockaddr *).
p For greater portability (such as newer protocol families) the new structure sockaddr_storage exists. .Li 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 family.
p .Fa namelen indicates the amount of space pointed to by .Fa name , in bytes. Upon return, .Fa namelen is set to the actual size of the returned address information.
p If the address of the destination socket for a given socket connection is needed, the .Xr getpeername 2 function should be used instead.
p If .Fa name does not point to enough space to hold the entire socket address, the result will be truncated to .Fa namelen bytes. .Sh RETURN VALUES On success, .Fn getsockname returns a 0, and .Fa namelen is set to the actual size of the socket address returned in .Fa name . Otherwise, .Va errno is set, and a value of -1 is returned. .Sh ERRORS The call succeeds unless: l -tag -width Er t Bq Er EBADF The argument .Fa s is not a valid descriptor. t Bq Er EFAULT The .Fa name parameter points to memory not in a valid part of the process address space. t Bq Er EINVAL The socket has been shut down. t Bq Er ENOBUFS Insufficient resources were available in the system to perform the operation. t Bq Er ENOTCONN The socket is not connected. t Bq Er ENOTSOCK The argument .Fa s is a file, not a socket. .El .Sh SEE ALSO .Xr bind 2 , .Xr socket 2 .Sh HISTORY The .Fn getsockname function call appeared in x 4.2 .
Indexes created Sat Sep 20 22:09:52 GMT 2025