1GETPEERNAME(2)             Linux Programmer's Manual            GETPEERNAME(2)
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NAME

6       getpeername - get name of connected peer socket
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SYNOPSIS

9       #include <sys/socket.h>
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11       int getpeername(int sockfd, struct sockaddr *restrict addr,
12                       socklen_t *restrict addrlen);
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DESCRIPTION

15       getpeername()  returns  the address of the peer connected to the socket
16       sockfd, in the buffer pointed to by addr.  The addrlen argument  should
17       be  initialized to indicate the amount of space pointed to by addr.  On
18       return it contains the actual size of the  name  returned  (in  bytes).
19       The name is truncated if the buffer provided is too small.
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21       The  returned address is truncated if the buffer provided is too small;
22       in this case, addrlen will return a value greater than was supplied  to
23       the call.
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RETURN VALUE

26       On  success,  zero is returned.  On error, -1 is returned, and errno is
27       set to indicate the error.
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ERRORS

30       EBADF  The argument sockfd is not a valid file descriptor.
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32       EFAULT The addr argument points to memory not in a valid  part  of  the
33              process address space.
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35       EINVAL addrlen is invalid (e.g., is negative).
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37       ENOBUFS
38              Insufficient  resources  were available in the system to perform
39              the operation.
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41       ENOTCONN
42              The socket is not connected.
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44       ENOTSOCK
45              The file descriptor sockfd does not refer to a socket.
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CONFORMING TO

48       POSIX.1-2001, POSIX.1-2008, SVr4, 4.4BSD (getpeername() first  appeared
49       in 4.2BSD).
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NOTES

52       For background on the socklen_t type, see accept(2).
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54       For stream sockets, once a connect(2) has been performed, either socket
55       can call getpeername() to obtain the address of the  peer  socket.   On
56       the  other  hand,  datagram  sockets  are connectionless.  Calling con‐
57       nect(2) on a datagram socket merely sets the peer address for  outgoing
58       datagrams  sent with write(2) or recv(2).  The caller of connect(2) can
59       use getpeername() to obtain the peer address that it  earlier  set  for
60       the  socket.   However, the peer socket is unaware of this information,
61       and calling getpeername() on the peer socket will return no useful  in‐
62       formation  (unless  a  connect(2)  call was also executed on the peer).
63       Note also that the receiver of a datagram can obtain the address of the
64       sender when using recvfrom(2).
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SEE ALSO

67       accept(2), bind(2), getsockname(2), ip(7), socket(7), unix(7)
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COLOPHON

70       This  page  is  part of release 5.12 of the Linux man-pages project.  A
71       description of the project, information about reporting bugs,  and  the
72       latest     version     of     this    page,    can    be    found    at
73       https://www.kernel.org/doc/man-pages/.
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77Linux                             2021-03-22                    GETPEERNAME(2)
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