getpeername(2) [netbsd man page]
GETPEERNAME(2) BSD System Calls Manual GETPEERNAME(2) NAME
getpeername -- get name of connected peer LIBRARY
Standard C Library (libc, -lc) SYNOPSIS
#include <sys/socket.h> int getpeername(int s, struct sockaddr * restrict name, socklen_t * restrict namelen); DESCRIPTION
The getpeername() function returns the name of the peer connected to the socket s. One common use occurs when a process inherits an open socket, such as TCP servers forked from inetd(8). In this scenario, getpeername() is used to determine the connecting client's IP address. The function takes three parameters: s contains the file descriptor of the socket whose peer should be looked up. name points to a sockaddr structure that will hold the address information for the connected peer. 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 sock- addr *). For greater portability, especially with the newer protocol families, the new struct sockaddr_storage should be used. sockaddr_storage is large enough to hold any of the other sockaddr_* variants. On return, it can be cast to the correct sock- addr type, based on the protocol family contained in its ss_family field. namelen indicates the amount of space pointed to by name, in bytes. If address information for the local end of the socket is required, the getsockname(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. RETURN VALUES
If the call succeeds, a 0 is returned 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. ERRORS
The call succeeds unless: [EBADF] The argument s is not a valid descriptor. [EFAULT] The name parameter points to memory not in a valid part of the process address space. [ENOBUFS] Insufficient resources were available in the system to perform the operation. [ENOTCONN] The socket is not connected. [ENOTSOCK] The argument s is a file, not a socket. SEE ALSO
accept(2), bind(2), getsockname(2), socket(2) STANDARDS
The function conforms to IEEE Std 1003.1-2008 (``POSIX.1''). HISTORY
The getpeername() function call appeared in 4.2BSD. BSD
June 3, 2011 BSD
Check Out this Related Man Page
getpeername(2) System Calls Manual getpeername(2) NAME
getpeername - Gets the name of the peer socket SYNOPSIS
#include <sys/socket.h> int getpeername ( int socket, struct sockaddr *address, socklen_t *address_len ); [XNS4.0] The definition of the getpeername() function in XNS4.0 uses a size_t data type instead of a socklen_t data type as specified in XNS5.0 (the previous definition). [Tru64 UNIX] The following definition of the getpeername() function does not conform to current standards and is supported only for back- ward compatibility (see standards(5)): int getpeername ( int socket, struct sockaddr *address, int *address_len ); STANDARDS
Interfaces documented on this reference page conform to industry standards as follows: getpeername(): XNS5.0 Refer to the standards(5) reference page for more information about industry standards and associated tags. PARAMETERS
Specifies the descriptor number of a connected socket. Points to a sockaddr structure, the format of which is determined by the domain and by the behavior requested for the socket. The sockaddr structure is an overlay for a sockaddr_in or sockaddr_un structure, depending on which of the supported address families is active. [Tru64 UNIX] If the compile-time option _SOCKADDR_LEN is defined before the sys/socket.h header file is included, the sockaddr structure takes 4.4BSD behavior, with a field for specifying the length of the socket address. Otherwise, the default 4.3BSD sock- addr structure is used, with the length of the socket address assumed to be 14 bytes or less. If _SOCKADDR_LEN is defined, the 4.3BSD sockaddr structure is defined with the name osockaddr. Specifies the length of the sockaddr structure pointed to by the address parameter. DESCRIPTION
The getpeername() function retrieves the name of the peer socket connected to the specified socket. If the actual length of the address is greater than the length of the sockaddr structure, the address is truncated. If the protocol permits connections by unbound clients and the peer is unbound, the value pointed to by address is unspecified. A process created by another process can inherit open sockets, but may need to identify the addresses of the sockets it has inherited. The getpeername() function allows a process to retrieve the address of the peer socket at the remote end of the socket connection. NOTES
The getpeername() function operates only on connected sockets. A process can use the getsockname() function to retrieve the local address of a socket. [Tru64 UNIX] When compiled in the X/Open UNIX environment or the POSIX.1g socket environment, calls to the getpeername() function are internally renamed by prepending _E to the function name. When you are debugging a module that includes the getpeername() function and for which _XOPEN_SOURCE_EXTENDED or _POSIX_PII_SOCKET has been defined, use _Egetpeername to refer to the getpeername() call. See standards(5) for further information. RETURN VALUES
Upon successful completion, a value of 0 (zero) is returned and the address parameter holds the address of the peer socket. If the get- peername() function fails, a value of -1 is returned and errno is set to indicate the error. ERRORS
If the getpeername() function fails, errno may be set to one of the following values: The socket parameter is not valid. The address or address_len parameter is not in a readable OR writable part of the user address space. The socket has been shut down. Insufficient resources were available in the system to complete the call. The available STREAMS resources were insufficient for the operation to com- plete. The socket is not connected. The socket parameter refers to a file, not a socket. The operation is not supported for the socket protocol. RELATED INFORMATION
Functions: accept(2), bind(2), getsockname(2), socket(2). Standards: standards(5). delim off getpeername(2)