Unix网络编程代码 第1章 简介

1.2 一个简单的时间获取客户程序

#include	<netinet/in.h>	/* sockaddr_in{} and other Internet defns */
#include    <strings.h>
#include	<stdarg.h>	/* ANSI C header file */
#include	<syslog.h>	/* for syslog() */
#include	<stdlib.h>
#include	<errno.h>
#include	<stdio.h>
#include	<string.h>
#include	<unistd.h>
#include	<arpa/inet.h>
#define	MAXLINE		4096	/* max text line length */
#define	SA	struct sockaddr
void err_doit(int errnoflag, const char *fmt, va_list ap)
{
	int errno_save;
	char buf[MAXLINE];

	errno_save = errno;	/* value caller might want printed */
	vsprintf(buf, fmt, ap);
	if (errnoflag)
		sprintf(buf + strlen(buf), ": %s", strerror(errno_save));
	strcat(buf, "\n");
	fflush(stdout);		/* in case stdout and stderr are the same */
	fputs(buf, stderr);
	fflush(stderr);		/* SunOS 4.1.* doesn't grok NULL argument */
	return;
}

void err_quit(const char *fmt, ...)
{
	va_list ap;

	va_start(ap, fmt);
	err_doit(0, fmt, ap);
	va_end(ap);
	exit(1);
}

void err_sys(const char *fmt, ...)
{
	va_list ap;

	va_start(ap, fmt);
	err_doit(1, fmt, ap);
	va_end(ap);
	exit(1);
}

int main(int argc, char **argv)
{
	int sockfd, n;
	char recvline[MAXLINE + 1];
	struct sockaddr_in servaddr;

	if (argc != 2)
		err_quit("usage: a.out <IPaddress>");

	if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0)
		err_sys("socket error");

	bzero(&servaddr, sizeof(servaddr));
	servaddr.sin_family = AF_INET;
	servaddr.sin_port = htons(13);	/* daytime server */
	if (inet_pton(AF_INET, argv[1], &servaddr.sin_addr) <= 0)
		err_quit("inet_pton error for %s", argv[1]);

	if (connect(sockfd, (SA *) & servaddr, sizeof(servaddr)) < 0)
		err_sys("connect error");

	while ((n = read(sockfd, recvline, MAXLINE)) > 0) {
		recvline[n] = 0;	/* null terminate */
		if (fputs(recvline, stdout) == EOF)
			err_sys("fputs error");
	}
	if (n < 0)
		err_sys("read error");

	exit(0);
}

1.5 一个简单的时间获取服务器程序

//注意，这个程序要root用户才可以运行，因为端口号是13,少于1024
#include	<strings.h>
#include	<time.h>
#include	<sys/socket.h>	/* basic socket definitions */
#include	<errno.h>
#include	<string.h>
#include	<unistd.h>
#include	<stdio.h>
#include	<stdlib.h>
#include	<netinet/in.h>	/* sockaddr_in{} and other Internet defns */
#include	<stdarg.h>	/* ANSI C header file */
#define	MAXLINE		4096	/* max text line length */
#define	LISTENQ		1024	/* 2nd argument to listen() */
#define	SA	struct sockaddr
void err_doit(int errnoflag, const char *fmt, va_list ap)
{
	int errno_save;
	char buf[MAXLINE];

	errno_save = errno;	/* value caller might want printed */
	vsprintf(buf, fmt, ap);
	if (errnoflag)
		sprintf(buf + strlen(buf), ": %s", strerror(errno_save));
	strcat(buf, "\n");
	fflush(stdout);		/* in case stdout and stderr are the same */
	fputs(buf, stderr);
	fflush(stderr);		/* SunOS 4.1.* doesn't grok NULL argument */
	return;
}

void err_sys(const char *fmt, ...)
{
	va_list ap;

	va_start(ap, fmt);
	err_doit(1, fmt, ap);
	va_end(ap);
	exit(1);
}

int Socket(int family, int type, int protocol)
{
	int n;

	if ((n = socket(family, type, protocol)) < 0)
		err_sys("socket error");
	return (n);
}

void Close(int fd)
{
	if (close(fd) == -1)
		err_sys("close error");
}

void Listen(int fd, int backlog)
{
	char *ptr;

	/*4can override 2nd argument with environment variable */
	if ((ptr = getenv("LISTENQ")) != NULL)
		backlog = atoi(ptr);

	if (listen(fd, backlog) < 0)
		err_sys("listen error");
}

int Accept(int fd, struct sockaddr *sa, socklen_t * salenptr)
{
	int n;

 again:if ((n = accept(fd, sa, salenptr)) < 0) {
#ifdef	EPROTO
		if (errno == EPROTO || errno == ECONNABORTED)
#else
		if (errno == ECONNABORTED)
#endif
			goto again;
		else
			err_sys("accept error");
	}
	return (n);
}

void Bind(int fd, const struct sockaddr *sa, socklen_t salen)
{
	if (bind(fd, sa, salen) < 0)
		err_sys("bind error");
}

void Write(int fd, void *ptr, int nbytes)
{
	if (write(fd, ptr, nbytes) != nbytes)
		err_sys("write error");
}

int main()
{
	int listenfd, connfd;
	struct sockaddr_in servaddr;
	char buff[MAXLINE];
	time_t ticks;

	listenfd = Socket(AF_INET, SOCK_STREAM, 0);

	bzero(&servaddr, sizeof(servaddr));
	servaddr.sin_family = AF_INET;
	servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
	servaddr.sin_port = htons(13);	/* daytime server */

	Bind(listenfd, (SA *) & servaddr, sizeof(servaddr));

	Listen(listenfd, LISTENQ);

	for (;;) {
		connfd = Accept(listenfd, (SA *) NULL, NULL);

		ticks = time(NULL);
		snprintf(buff, sizeof(buff), "%.24s\r\n", ctime(&ticks));
		Write(connfd, buff, strlen(buff));

		Close(connfd);
	}
}