In-depth understanding of shutdown and close Functions

Shutdown can be used to close the read and write ends,

Shut down the read end and tell the kernel to stop receiving data.

Close the write end and send only one closed handshake, that is, one fin.

Shutdown can only shut down writing or reading. The shutdown of FD must be closed. Otherwise, FD will grow at the same time.

When the FD is closed, if the FD has a count, it will not be sent until the count is 0.

When a single process processes FD with multiple threads, You need to construct the FD counter to close the FD.