memset(&server, 0, sizeof(SOCKADDR_IN));

This line of code initializes the memory block for the server variable to all zeros. The server variable is a structure of type SOCKADDR_IN, which is used to store information about a socket address for an Internet Protocol (IP) network. The memset function is a standard C library function that sets a block of memory to a specified value. In this case, it sets the memory block for the server variable to all zeros, which effectively initializes all fields in the structure to their default values. This is a common practice when working with structures in C, as it ensures that all fields are properly initialized before they are used.