unix网络编程各种TCP客户-服务器程序设计实例（三）

第五种  TCP预先派生子进程服务器程序：

对预先派生子进程服务器的最后一种改动就是由父进程调用accept，然后再将所接受的已连接描述字传递给子进程。父进程必须跟踪子进程的忙闲状态，以便给空闲子进程传递新的描述字。为每个子进程维护一个信息结构，用来管理各子进程。

在调用fork之前，先创建一个字节流管道（Unix域的字节流套接口），它是Unix域的字节流套接口。当子进程派生后，父进程关闭一个描述字（sockfd[1]），子进程关闭另一个描述字（sockfd[0]）,此外，子进程将流管道的字节所在端（sockfd[1]）复制到标准输出。

child.h:

typedef struct {
  pid_t		child_pid;		/* process ID */
  int		child_pipefd;	/* parent's stream pipe to/from child */
  int		child_status;	/* 0 = ready */
  long		child_count;	/* # connections handled */
} Child;

Child	*cptr;		/* array of Child structures; calloc'ed */

Child.c:

/* include child_make */
#include	"unp.h"
#include	"child.h"

Child	*cptr;		/* array of Child structures; calloc'ed */
pid_t
child_make(int i, int listenfd, int addrlen)
{
	int		sockfd[2];
	pid_t	pid;
	void	child_main(int, int, int);

	Socketpair(AF_LOCAL, SOCK_STREAM, 0, sockfd);

	if ( (pid = Fork()) > 0) {
		Close(sockfd[1]);
		cptr[i].child_pid = pid;
		cptr[i].child_pipefd = sockfd[0];
		cptr[i].child_status = 0;
		return(pid);		/* parent */
	}

	Dup2(sockfd[1], STDERR_FILENO);		/* child's stream pipe to parent */
	Close(sockfd[0]);
	Close(sockfd[1]);
	Close(listenfd);					/* child does not need this open */
	child_main(i, listenfd, addrlen);	/* never returns */
}
/* end child_make */

/* include child_main */
void
child_main(int i, int listenfd, int addrlen)
{
	char			c;
	int				connfd;
	ssize_t			n;
	void			web_child(int);

	printf("child %ld starting\n", (long) getpid());
	for ( ; ; ) {
		if ( (n = Read_fd(STDERR_FILENO, &c, 1, &connfd)) == 0)
			err_quit("read_fd returned 0");
		if (connfd < 0)
			err_quit("no descriptor from read_fd");

		web_child(connfd);				/* process request */
		Close(connfd);

		Write(STDERR_FILENO, "", 1);	/* tell parent we're ready again */
	}
}
/* end child_main */

pr_cpu_time.c:

#include	"unp.h"
#include	<sys/resource.h>

#ifndef	HAVE_GETRUSAGE_PROTO
int		getrusage(int, struct rusage *);
#endif

void
pr_cpu_time(void)
{
	double			user, sys;
	struct rusage	myusage, childusage;

	if (getrusage(RUSAGE_SELF, &myusage) < 0)
		err_sys("getrusage error");
	if (getrusage(RUSAGE_CHILDREN, &childusage) < 0)
		err_sys("getrusage error");

	user = (double) myusage.ru_utime.tv_sec +
					myusage.ru_utime.tv_usec/1000000.0;
	user += (double) childusage.ru_utime.tv_sec +
					 childusage.ru_utime.tv_usec/1000000.0;
	sys = (double) myusage.ru_stime.tv_sec +
				   myusage.ru_stime.tv_usec/1000000.0;
	sys += (double) childusage.ru_stime.tv_sec +
					childusage.ru_stime.tv_usec/1000000.0;

	printf("\nuser time = %g, sys time = %g\n", user, sys);
}

web_child.c:

#include	"unp.h"

#define	MAXN	16384		/* max # bytes client can request */

void
web_child(int sockfd)
{
	int			ntowrite;
	ssize_t		nread;
	char		line[MAXLINE], result[MAXN];

	for ( ; ; ) {
		if ( (nread = Readline(sockfd, line, MAXLINE)) == 0)
			return;		/* connection closed by other end */

			/* 4line from client specifies #bytes to write back */
		ntowrite = atol(line);
		if ((ntowrite <= 0) || (ntowrite > MAXN))
			err_quit("client request for %d bytes", ntowrite);

		Writen(sockfd, result, ntowrite);
	}
}

 

client.c:

#include	"unp.h"

#define	MAXN	16384		/* max # bytes to request from server */

int
main(int argc, char **argv)
{
	int		i, j, fd, nchildren, nloops, nbytes;
	pid_t	pid;
	ssize_t	n;
	char	request[MAXLINE], reply[MAXN];

	if (argc != 6)
		err_quit("usage: client <hostname or IPaddr> <port> <#children> "
				 "<#loops/child> <#bytes/request>");

	nchildren = atoi(argv[3]);
	nloops = atoi(argv[4]);
	nbytes = atoi(argv[5]);
	snprintf(request, sizeof(request), "%d\n", nbytes); /* newline at end */

	for (i = 0; i < nchildren; i++) {
		if ( (pid = Fork()) == 0) {		/* child */
			for (j = 0; j < nloops; j++) {
				fd = Tcp_connect(argv[1], argv[2]);

				Write(fd, request, strlen(request));

				if ( (n = Readn(fd, reply, nbytes)) != nbytes)
					err_quit("server returned %d bytes", n);

				Close(fd);		/* TIME_WAIT on client, not server */
			}
			printf("child %d done\n", i);
			exit(0);
		}
		/* parent loops around to fork() again */
	}

	while (wait(NULL) > 0)	/* now parent waits for all children */
		;
	if (errno != ECHILD)
		err_sys("wait error");

	exit(0);
}

server.c:

/* include serv05a */
#include	"unp.h"
#include	"child.h"

static int		nchildren;

int
main(int argc, char **argv)
{
	int			listenfd, i, navail, maxfd, nsel, connfd, rc;
	void		sig_int(int);
	pid_t		child_make(int, int, int);
	ssize_t		n;
	fd_set		rset, masterset;
	socklen_t	addrlen, clilen;
	struct sockaddr	*cliaddr;

	if (argc == 3)
		listenfd = Tcp_listen(NULL, argv[1], &addrlen);
	else if (argc == 4)
		listenfd = Tcp_listen(argv[1], argv[2], &addrlen);
	else
		err_quit("usage: serv05 [ <host> ] <port#> <#children>");

	FD_ZERO(&masterset);
	FD_SET(listenfd, &masterset);
	maxfd = listenfd;
	cliaddr = Malloc(addrlen);

	nchildren = atoi(argv[argc-1]);
	navail = nchildren;
	cptr = Calloc(nchildren, sizeof(Child));

		/* 4prefork all the children */
	for (i = 0; i < nchildren; i++) {
		child_make(i, listenfd, addrlen);	/* parent returns */
		FD_SET(cptr[i].child_pipefd, &masterset);
		maxfd = max(maxfd, cptr[i].child_pipefd);
	}

	Signal(SIGINT, sig_int);

	for ( ; ; ) {
		rset = masterset;
		if (navail <= 0)
			FD_CLR(listenfd, &rset);	/* turn off if no available children */
		nsel = Select(maxfd + 1, &rset, NULL, NULL, NULL);

			/* 4check for new connections */
		if (FD_ISSET(listenfd, &rset)) {
			clilen = addrlen;
			connfd = Accept(listenfd, cliaddr, &clilen);

			for (i = 0; i < nchildren; i++)
				if (cptr[i].child_status == 0)
					break;				/* available */

			if (i == nchildren)
				err_quit("no available children");
			cptr[i].child_status = 1;	/* mark child as busy */
			cptr[i].child_count++;
			navail--;

			n = Write_fd(cptr[i].child_pipefd, "", 1, connfd);
			Close(connfd);
			if (--nsel == 0)
				continue;	/* all done with select() results */
		}

			/* 4find any newly-available children */
		for (i = 0; i < nchildren; i++) {
			if (FD_ISSET(cptr[i].child_pipefd, &rset)) {
				if ( (n = Read(cptr[i].child_pipefd, &rc, 1)) == 0)
					err_quit("child %d terminated unexpectedly", i);
				cptr[i].child_status = 0;
				navail++;
				if (--nsel == 0)
					break;	/* all done with select() results */
			}
		}
	}
}
/* end serv05a */

void
sig_int(int signo)
{
	int		i;
	void	pr_cpu_time(void);

		/* 4terminate all children */
	for (i = 0; i < nchildren; i++)
		kill(cptr[i].child_pid, SIGTERM);
	while (wait(NULL) > 0)		/* wait for all children */
		;
	if (errno != ECHILD)
		err_sys("wait error");

	pr_cpu_time();

	for (i = 0; i < nchildren; i++)
		printf("child %d, %ld connections\n", i, cptr[i].child_count);

	exit(0);
}

编译命令：

gcc server.c child.c pr_cpu_time.c web_child.c -o server -lunp