Move semantics and rvalue references

Copy semantics are for creating clones of objects. It is useful sometimes, but not always needed or even meaningful. Consider the following class that encapsulates a TCP client socket. A TCP socket is an integer that represents one endpoint of a TCP connection and through which data can be sent or received to the other endpoint. The TCP socket class can have the following interface:

class TCPSocket
{
public:
  TCPSocket(const std::string& host, const std::string& port);
  ~TCPSocket();

  bool is_open();
  vector<char> read(size_t to_read);
  size_t write(vector<char> payload);

private:
  int socket_fd_;

  TCPSocket(const TCPSocket&);
  TCPSocket& operator = (const TCPSocket&);
};

The constructor opens a connection to a host on a specified port and initializes the socket_fd_ member variable. The destructor closes the connection. TCP does not define a way to make clones of open sockets (unlike file descriptors with dup...