What is the Difference Between read() and recv() , and Between send() and write()?

The difference is that recv()/send() work only on socket descriptors and let you specify certain options for the actual operation. Those functions are slightly more specialized (for instance, you can set a flag to ignore SIGPIPE, or to send out-of-band messages...).

Functions read()/write() are the universal file descriptor functions working on all descriptors.

Per the first hit on Google

read() is equivalent to recv() with a flags parameter of 0. Other values for the flags parameter change the behaviour of recv(). Similarly, write() is equivalent to send() with flags == 0.

read() and write() are more generic, they work with any file descriptor. However, they won't work on Windows.

You can pass additional options to send() and recv(), so you may have to used them in some cases.