modern laptops only have VGA and USB ports. Can somebody tell me how I can send signals to a hardware using VGA or USB port instead of parallel port or serial port; since new laptops do not come with parallel or serial port.
I'm not sure I understand the question. VGA is for video; it's not normally used for interfacing to anything other than a video device. If your hardware has a USB port then you can connect it to the USB port of your computer. You don't say what kind of signals you are trying to connect. You can always add an inexpensive digital I/O card to a computer to provide a simple interface. Or a serial card, if that's what you want.
They can be found on eBay for less than $5 shipping included.
These device not only offer a virtual COM port to send data through the USB to a TTL UART, they also offer several TTL I/O lines which can be controlled by software on the PC.
They have been successfully used as programmers, USB to Serial converters, JTAG, etc.