/* *	socklib.c * *	This file contains functions used lots when writing internet *	client/server programs.  The two main functions here are: * *	make_server_socket( portnum )	returns a server socket *					or -1 if error *      make_server_socket_q(portnum,backlog) * *	connect_to_server(char *hostname, int portnum) *					returns a connected socket *					or -1 if error */ #include	<stdio.h>#include	<unistd.h>#include	<sys/types.h>#include	<sys/socket.h>#include	<netinet/in.h>#include	<netdb.h>#include	<time.h>#include	<strings.h>#define   HOSTLEN  256#define	  BACKLOG  1int make_server_socket_q(int , int );int make_server_socket(int portnum){	return make_server_socket_q(portnum, BACKLOG);}int make_server_socket_q(int portnum, int backlog){	struct  sockaddr_in   saddr;   /* build our address here */	struct	hostent		*hp;   /* this is part of our    */	char	hostname[HOSTLEN];     /* address 	         */	int	sock_id;	       /* the socket             */	sock_id = socket(PF_INET, SOCK_STREAM, 0);  /* get a socket */	if ( sock_id == -1 ) 		return -1;	/** build address and bind it to socket **/	bzero((void *)&saddr, sizeof(saddr));   /* clear out struct     */	gethostname(hostname, HOSTLEN);         /* where am I ?         */	hp = gethostbyname(hostname);           /* get info about host  */	                                        /* fill in host part    */	bcopy( (void *)hp->h_addr, (void *)&saddr.sin_addr, hp->h_length);	saddr.sin_port = htons(portnum);        /* fill in socket port  */	saddr.sin_family = AF_INET ;            /* fill in addr family  */	if ( bind(sock_id, (struct sockaddr *)&saddr, sizeof(saddr)) != 0 )	       return -1;	/** arrange for incoming calls **/	if ( listen(sock_id, backlog) != 0 ) 		return -1;	return sock_id;}int connect_to_server(char *host, int portnum){	int sock;	struct sockaddr_in  servadd;        /* the number to call */	struct hostent      *hp;            /* used to get number */	/** Step 1: Get a socket **/	sock = socket( AF_INET, SOCK_STREAM, 0 );    /* get a line   */	if ( sock == -1 ) 		return -1;	/** Step 2: connect to server **/	bzero( &servadd, sizeof(servadd) );     /* zero the address     */	hp = gethostbyname( host );             /* lookup host's ip #   */	if (hp == NULL) 		return -1;	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,(struct sockaddr *)&servadd, sizeof(servadd)) !=0)	       return -1;	return sock;}