Anyone can you please answer?
A socket is a point of connection between a peripheral hardware block and the FX3 RAM. Each peripheral hardware block on FX3, such as USB, GPIF, UART, and SPI, has a fixed number of sockets associated with it. The number of independent data flows through a peripheral is equal to the number of its sockets.
GPIF block has got 32 sockets associated with it.
To use P Port, let's say, you need to make communication between P Port and U-Port(USB)
Then you should create a DMA channel between these two blocks. The point of connection between this channel and the P-port block/U-port block would be their respective sockets.
For detailed explanation of Sockets and it's usage in AN75779(UVC Application) please read the appnote document.