(libc.info.gz) Socket Addresses

(libc.info.gz) Communication Styles
 
 16.3 Socket Addresses
 =====================
 
 The name of a socket is normally called an "address".  The functions and
 symbols for dealing with socket addresses were named inconsistently,
 sometimes using the term "name" and sometimes using "address".  You can
 regard these terms as synonymous where sockets are concerned.
 
    A socket newly created with the 'socket' function has no address.
 Other processes can find it for communication only if you give it an
 address.  We call this "binding" the address to the socket, and the way
 to do it is with the 'bind' function.
 
    You need be concerned with the address of a socket if other processes
 are to find it and start communicating with it.  You can specify an
 address for other sockets, but this is usually pointless; the first time
 you send data from a socket, or use it to initiate a connection, the
 system assigns an address automatically if you have not specified one.
 
    Occasionally a client needs to specify an address because the server
 discriminates based on address; for example, the rsh and rlogin
 protocols look at the client's socket address and only bypass password
 checking if it is less than 'IPPORT_RESERVED' ( Ports).
 
    The details of socket addresses vary depending on what namespace you
 are using.   Local Namespace, or  Internet Namespace, for
 specific information.
 
    Regardless of the namespace, you use the same functions 'bind' and
 'getsockname' to set and examine a socket's address.  These functions
 use a phony data type, 'struct sockaddr *', to accept the address.  In
 practice, the address lives in a structure of some other data type
 appropriate to the address format you are using, but you cast its
 address to 'struct sockaddr *' when you pass it to 'bind'.
(libc.info.gz) Socket Addresses

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