Converting protocol names into protocol numbers

The getprotobyname() function converts a protocol name into a protocol number. The protocol name is passed when getprotobyname() is called.

As its result getprotobyname() returns a pointer to an object of data type struct protoent.

The protoent structure is declared as follows:

struct protoent {
     char *p_name;          /* Official protocol name */
     char **p_aliases;      /* Alias list */
     int  p_proto;          /* Protocol number */
};