(PHP 4 >= 4.1.0, PHP 5)
socket_getpeername — Queries the remote side of the given socket which may either result in host/port or in a Unix filesystem path, dependent on its type
$socket
   , string &$address
   [, int &$port
  ] )Queries the remote side of the given socket which may either result in host/port or in a Unix filesystem path, dependent on its type.
socketA valid socket resource created with socket_create() or socket_accept().
address
       If the given socket is of type AF_INET or
       AF_INET6, socket_getpeername()
       will return the peers (remote) IP address in
       appropriate notation (e.g. 127.0.0.1 or
       fe80::1) in the address
       parameter and, if the optional port parameter is
       present, also the associated port.
      
       If the given socket is of type AF_UNIX,
       socket_getpeername() will return the Unix filesystem
       path (e.g. /var/run/daemon.sock) in the
       address parameter.
      
port
       If given, this will hold the port associated to
       address.
      
   Returns TRUE on success or FALSE on failure. socket_getpeername() may also return
   FALSE if the socket type is not any of AF_INET,
   AF_INET6, or AF_UNIX, in which
   case the last socket error code is not updated.
  
Note:
socket_getpeername() should not be used with
AF_UNIXsockets created with socket_accept(). Only sockets created with socket_connect() or a primary server socket following a call to socket_bind() will return meaningful values.
Note:
For having socket_getpeername() to return a meaningful value, the socket it is applied upon must of course be one for which the concept of "peer" makes sense.