Which of the following statements are true?

Question $56$Select one or more:

a$.$

A socket is a kind of opening.

b$.$

A socket represents one endpoint of a network connection.

c$.$

A program uses a socket to communicate with another program over the network.

d$.$

Data written by a program to the socket at one end of the connection is transmitted to the socket on the other end of the connection, where it can be read by the program at that end.