@property<EOL><INDENT>def s_fd(self):<DEDENT>
try:<EOL><INDENT>return -<NUM_LIT:1> if self.socket_instance is None else self.socket_instance.fileno()<EOL><DEDENT>except socket.error:<EOL><INDENT>return -<NUM_LIT:1><EOL><DEDENT>
Return the file descriptor number of the open socket or -1.