tcpdaytimed.c

tcp 时间服务程序

/* TCPdaytimed.c :一个使用循环的、面向连接的时间服务的服务器*/

#include <sys/types.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <sys/wait.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/errno.h>
#include <netdb.h>

#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <stdarg.h>
#include <unistd.h> /* close */


#define SUCCESS 0
#define ERROR   1

#define QLEN 32   /*maxinum connection queue length*/

extern int            errno;

/* function */
void  TCPdaytimed(int fd);
int  errexit(const char *format, ...);
int  passiveTCP(const char *service, int qlen);

/*------------------------------------------------------
 *  main -Iterative TCP server for DAYTIME service
 *------------------------------------------------------
 */
int main (int argc, char *argv[]) 
{  
	char       *service = "daytime";  /*service name or port number*/
	struct sockaddr_in    fsin;    /*the address of a client*/
	unsigned int          alen;    /*length of client's address*/
	int                   msock;   /*master server socket*/
	int                   ssock;   /*slave server socket*/
	
	switch (argc){
		case    1:
			break;
		case    2:
			service = argv[1];
			break;
		default:
			errexit("usage: TCPdaytimed[port]\n");
		}
	
	msock = passiveTCP(service, QLEN);
	
	while (1) {
		alen = sizeof(fsin);
		ssock = accept(msock, (struct sockaddr *)&fsin, &alen);
		if (ssock < 0) 
			errexit("accept: %s\n", strerror(errno));
		TCPdaytimed(ssock);
		(void) close(ssock);
	}
}

/*------------------------------------------------------
 *  TCPdaytimed - do TCP DAYTIME protocol
 *------------------------------------------------------
 */
void TCPdaytimed(int fd)
{
	char    *pts; /*pointer to time string*/
	time_t  now;  /*current time*/
	char    *ctime();
	
	(void) time(&now);
	pts = ctime(&now);
	(void) write(fd, pts, strlen(pts));
}

/*--------------------------------------------------------------
 *  passiveTCP - create a passive socket for use in a TCP server
 *--------------------------------------------------------------
 */	
int passiveTCP(const char *service, int qlen)
/*
 *  Arguments:
 *      service - service associated with the desired port
 *      qlen    - maxinum server request queue length
 */
{
	return passivesock(service, "tcp", qlen);
}

/*--------------------------------------------------------------
 *  passivesock - allocate & bind a server socket using TCP or UDP
 *--------------------------------------------------------------
 */	
int passivesock(const char *service, const char *transport, int qlen)
/*
 *  Arguments:
 *      service - service associated with the desired port
 *      transport - transport protocol to user ("tcp" or "udp")
 *      qlen    - maxinum server request queue length
 */
{
	struct servent  *pse;  /*pointer to service information entry*/
	struct protoent *ppe;  /*pointer to protocol information entry*/
	struct sockaddr_in sin; /*an Internet endpoint address*/
	int          s, type;  /*socket descripter and socket type*/
	
	memset(&sin, 0, sizeof(sin));
	sin.sin_family = AF_INET;
	sin.sin_addr.s_addr = INADDR_ANY;
	
	/*Map service name to port number*/
	if (pse = getservbyname(service, transport))
		sin.sin_port = htons(ntohs((unsigned short(pse->s_port) + portbase);
	else if ((sin.sin_port = htons((unsigned short)atoi(service))) == 0)
		errexit("can't get \"%s\" service entry\n", service);
		
	/*Map protocol name to protocol number*/
	if ((ppe = getprotobyname(transport)) == 0)
		errexit("can't get \"%s\" protocol entry\n", transport);
	
	/*Use protocol to choose a socket type*/
	if (strcmp(transport, "udp") == 0)
		type = SOCK_DGRAM;
	else
		type = SOCK_STREAM;
		
	/*Allocate a socket*/
	s = socket(PE_INET, type, ppe->p_proto);
	if (s < 0)
		errexit("can't create socket: %s\n", strerror(errno));
	
	/*Bind the socket*/
	if (bind(s, (struct sockaddr *)&sin, sizeof(sin)) < 0)
		errexit("can't bind to %s port: %s\n", service, strerror(errno));
	if (type == SOCK_STREAM && listen(s, qlen) < 0)
		errexit("can't listen on %s port: %s\n", service, strerror(errno));
	return s;
}

/*------------------------------------------------------
 *  errexit - print an error message and exit
 *------------------------------------------------------
 */
int errexit(const char * format, ...)
{
	va_list  args;
	
	va_start(args, format);
	vfprintf(stderr, format, args);
	va_end(args);
	exit(1);
}