/* rls.c - a client for a remote directory listing service *         usage: rls hostname directory */#include       <stdio.h>#include       <sys/types.h>#include       <sys/socket.h>#include       <netinet/in.h>#include       <netdb.h>#define        oops(msg)       { perror(msg); exit(1); }#define		PORTNUM		15000main(int ac, char *av[]){	struct sockaddr_in  servadd;        /* the number to call */	struct hostent      *hp;            /* used to get number */	int    sock_id, sock_fd;            /* the socket and fd  */	char   buffer[BUFSIZ];              /* to receive message */	int    n_read;                      /* for message length */	if ( ac != 3 ) exit(1);     /** Step 1: Get a socket **/	sock_id = socket( AF_INET, SOCK_STREAM, 0 );    /* get a line   */	if ( sock_id == -1 ) 		oops( "socket" );          		/* or fail      */     /** Step 2: connect to server **/	bzero( &servadd, sizeof(servadd) );     /* zero the address     */	hp = gethostbyname( av[1] );            /* lookup host's ip #   */	if (hp == NULL) 		oops(av[1]);            	/* or die               */	bcopy(hp->h_addr, (struct sockaddr *)&servadd.sin_addr, hp->h_length);	servadd.sin_port = htons(PORTNUM);      /* fill in port number  */	servadd.sin_family = AF_INET ;          /* fill in socket type  */	if ( connect(sock_id,(struct sockaddr *)&servadd, sizeof(servadd)) !=0)	       oops( "connect" );     /** Step 3: send directory name, then read back results **/	if ( write(sock_id, av[2], strlen(av[2])) == -1)		oops("write");	if ( write(sock_id, "\n", 1) == -1 )		oops("write");	while( (n_read = read(sock_id, buffer, BUFSIZ)) > 0 )		if ( write(1, buffer, n_read) == -1 )			oops("write");	close( sock_id );    }