Converting protocol names to protocol numbers

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

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

The protoent structure is declared in <netdb.h> as follows:

struct protoent {
     char *p_name;          /* official protocol name */
     char **p_aliases;      /* alias list */
     int  p_proto;          /* protocol number */
};