14.3 Sockets and Socket Portals

The RWSocketPortal class uses the "resource acquisition is initialization" technique to avoid the problems described in the previous section. Since RWSocketPortal uses the interface-implementation pattern described in Chapter 11, copy and assignment semantics do the appropriate thing.

You can get a copy of the socket inside a socket portal. All of the functionality of sockets is then made available to you. For example, suppose code that uses socket portals needs to print out a line describing both ends of the connection. Here is one way to do this:

RWSocket sock = sockPortal.socket();                         //1
cout << sock.id();                                           //2

`//1`	Make a copy of the socket used by the *RWSocketPortal* `sockPortal`. The socket returned refers to the same communications channel as the socket portal. Since the socket portal automatically closes this channel once all *RWSocketPortal* references to the channel are gone, the *RWSocket* should only be used while the *RWSocketPortal* is in scope.
`//2`	Print out an identifier giving both ends of the connection.

We could also have accomplished this in one line, by using a temporary socket:

cout << sockPortal.socket().id();

By using a temporary variable, the lifetime of the RWSocket is guaranteed to be as short as the socket portal's lifetime.

Since the socket member function returns a new socket, and not a reference to the actual socket used by the RWSocketPortal you can't reassign the portal's socket like this:

socketPortal.socket() = anotherSocket;  // Nope!