socklib.c

unix linux 编程实践源代码

/*
 *	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  1

int 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;
}