(libc.info)Reading Address


Reading the Address of a Socket
-------------------------------

   Use the function `getsockname' to examine the address of an Internet
socket.  The prototype for this function is in the header file
`sys/socket.h'.

 - Function: int getsockname (int SOCKET, struct sockaddr *ADDR,
          socklen_t *LENGTH-PTR)
     The `getsockname' function returns information about the address
     of the socket SOCKET in the locations specified by the ADDR and
     LENGTH-PTR arguments.  Note that the LENGTH-PTR is a pointer; you
     should initialize it to be the allocation size of ADDR, and on
     return it contains the actual size of the address data.

     The format of the address data depends on the socket namespace.
     The length of the information is usually fixed for a given
     namespace, so normally you can know exactly how much space is
     needed and can provide that much.  The usual practice is to
     allocate a place for the value using the proper data type for the
     socket's namespace, then cast its address to `struct sockaddr *'
     to pass it to `getsockname'.

     The return value is `0' on success and `-1' on error.  The
     following `errno' error conditions are defined for this function:

    `EBADF'
          The SOCKET argument is not a valid file descriptor.

    `ENOTSOCK'
          The descriptor SOCKET is not a socket.

    `ENOBUFS'
          There are not enough internal buffers available for the
          operation.

   You can't read the address of a socket in the file namespace.  This
is consistent with the rest of the system; in general, there's no way to
find a file's name from a descriptor for that file.


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