continued work on tcp_client class:
	bool connect(void);
    	bool set_rx_buffer_size(int);
    	bool set_tx_buffer_size(int);
    	bool connected(void);
    	size_t read(void *, size_t, size_t);
    	size_t write(void *, size_t, size_t);
    	int format_write(const char *, int, int);
    	int tx_flush(void);
    	int rx_flush(void);