第3章 套接字编程简介
3.4 字节排序函数
#include <stdio.h>
#include <stdlib.h>
#define CPU_VENDOR_OS "i686-pc-linux-gnu"
int main(int argc, char **argv)
{
union {
short s;
char c[sizeof(short)];
} un;
un.s = 0x0102;
printf("%s: ", CPU_VENDOR_OS);
if (sizeof(short) == 2) {
if (un.c[0] == 1 && un.c[1] == 2)
printf("big-endian\n");
else if (un.c[0] == 2 && un.c[1] == 1)
printf("little-endian\n");
else
printf("unknown\n");
} else
printf("sizeof(short) = %d\n", sizeof(short));
exit(0);
}
第5章 TCP客户/服务器程序示例
5.2 TCP回射服务器程序
#include <strings.h>
#include <sys/types.h> /* basic system data types */
#include <sys/socket.h> /* basic socket definitions */
#include <netinet/in.h> /* sockaddr_in{} and other Internet defns */
#include <stdarg.h> /* ANSI C header file */
#include <syslog.h> /* for syslog() */
#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
int daemon_proc; /* set nonzero by daemon_init() */
#define SA struct sockaddr
#define MAXLINE 4096 /* max text line length */
#define SERV_PORT 9877 /* TCP and UDP */
#define LISTENQ 1024 /* 2nd argument to listen() */
void err_doit(int errnoflag, int level, const char *fmt, va_list ap)
{
int errno_save, n;
char buf[MAXLINE + 1];
errno_save = errno; /* value caller might want printed */
#ifdef HAVE_VSNPRINTF
vsnprintf(buf, MAXLINE, fmt, ap); /* safe */
#else
vsprintf(buf, fmt, ap); /* not safe */
#endif
n = strlen(buf);
if (errnoflag)
snprintf(buf + n, MAXLINE - n, ": %s", strerror(errno_save));
strcat(buf, "\n");
if (daemon_proc) {
syslog(level, "%s",buf);
} else {
fflush(stdout); /* in case stdout and stderr are the same */
fputs(buf, stderr);
fflush(stderr);
}
return;
}
void err_sys(const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
err_doit(1, LOG_ERR, 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 Bind(int fd, const struct sockaddr *sa, socklen_t salen)
{
if (bind(fd, sa, salen) < 0)
err_sys("bind 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);
}
pid_t Fork(void)
{
pid_t pid;
if ((pid = fork()) == -1)
err_sys("fork error");
return (pid);
}
void Close(int fd)
{
if (close(fd) == -1)
err_sys("close error");
}
ssize_t /* Write "n" bytes to a descriptor. */
writen(int fd, const void *vptr, size_t n)
{
size_t nleft;
ssize_t nwritten;
const char *ptr;
ptr = (const char *)vptr;
nleft = n;
while (nleft > 0) {
if ((nwritten = write(fd, ptr, nleft)) <= 0) {
if (nwritten < 0 && errno == EINTR)
nwritten = 0; /* and call write() again */
else
return (-1); /* error */
}
nleft -= nwritten;
ptr += nwritten;
}
return (n);
}
void Writen(int fd, void *ptr, int nbytes)
{
if (writen(fd, ptr, nbytes) != nbytes)
err_sys("writen error");
}
void str_echo(int sockfd)
{
ssize_t n;
char buf[MAXLINE];
again:
while ((n = read(sockfd, buf, MAXLINE)) > 0)
Writen(sockfd, buf, n);
if (n < 0 && errno == EINTR)
goto again;
else if (n < 0)
err_sys("str_echo: read error");
}
int main()
{
int listenfd, connfd;
pid_t childpid;
socklen_t clilen;
struct sockaddr_in cliaddr, servaddr;
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(SERV_PORT);
Bind(listenfd, (SA *) & servaddr, sizeof(servaddr));
Listen(listenfd, LISTENQ);
for (;;) {
clilen = sizeof(cliaddr);
connfd = Accept(listenfd, (SA *) & cliaddr, &clilen);
if ((childpid = Fork()) == 0) { /* child process */
Close(listenfd); /* close listening socket */
str_echo(connfd); /* process the request */
exit(0);
}
Close(connfd); /* parent closes connected socket */
}
}
5.4 TCP回射客户程序
#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 <errno.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <arpa/inet.h>
#include <unistd.h>
#define MAXLINE 4096 /* max text line length */
#define SERV_PORT 9877 /* TCP and UDP */
int daemon_proc; /* set nonzero by daemon_init() */
#define SA struct sockaddr
void err_doit(int errnoflag, int level, const char *fmt, va_list ap)
{
int errno_save, n;
char buf[MAXLINE + 1];
errno_save = errno; /* value caller might want printed */
#ifdef HAVE_VSNPRINTF
vsnprintf(buf, MAXLINE, fmt, ap); /* safe */
#else
vsprintf(buf, fmt, ap); /* not safe */
#endif
n = strlen(buf);
if (errnoflag)
snprintf(buf + n, MAXLINE - n, ": %s", strerror(errno_save));
strcat(buf, "\n");
if (daemon_proc) {
syslog(level, "%s",buf);
} else {
fflush(stdout); /* in case stdout and stderr are the same */
fputs(buf, stderr);
fflush(stderr);
}
return;
}
void err_quit(const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
err_doit(0, LOG_ERR, fmt, ap);
va_end(ap);
exit(1);
}
void err_sys(const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
err_doit(1, LOG_ERR, 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 Inet_pton(int family, const char *strptr, void *addrptr)
{
int n;
if ((n = inet_pton(family, strptr, addrptr)) < 0)
err_sys("inet_pton error for %s", strptr); /* errno set */
else if (n == 0)
err_quit("inet_pton error for %s", strptr); /* errno not set */
/* nothing to return */
}
void Connect(int fd, const struct sockaddr *sa, socklen_t salen)
{
if (connect(fd, sa, salen) < 0)
err_sys("connect error");
}
ssize_t writen(int fd, const void *vptr, size_t n)
{
size_t nleft;
ssize_t nwritten;
const char *ptr;
ptr = (const char *)vptr;
nleft = n;
while (nleft > 0) {
if ((nwritten = write(fd, ptr, nleft)) <= 0) {
if (nwritten < 0 && errno == EINTR)
nwritten = 0; /* and call write() again */
else
return (-1); /* error */
}
nleft -= nwritten;
ptr += nwritten;
}
return (n);
}
void Writen(int fd, void *ptr, int nbytes)
{
if (writen(fd, ptr, nbytes) != nbytes)
err_sys("writen error");
}
char *Fgets(char *ptr, int n, FILE * stream)
{
char *rptr;
if ((rptr = fgets(ptr, n, stream)) == NULL && ferror(stream))
err_sys("fgets error");
return (rptr);
}
void Fputs(const char *ptr, FILE * stream)
{
if (fputs(ptr, stream) == EOF)
err_sys("fputs error");
}
static int read_cnt;
static char *read_ptr;
static char read_buf[MAXLINE];
static ssize_t my_read(int fd, char *ptr)
{
if (read_cnt <= 0) {
again:
if ((read_cnt = read(fd, read_buf, sizeof(read_buf))) < 0) {
if (errno == EINTR)
goto again;
return (-1);
} else if (read_cnt == 0)
return (0);
read_ptr = read_buf;
}
read_cnt--;
*ptr = *read_ptr++;
return (1);
}
ssize_t readline(int fd, void *vptr, int maxlen)
{
ssize_t n, rc;
char c, *ptr;
ptr = (char *)vptr;
for (n = 1; n < maxlen; n++) {
if ((rc = my_read(fd, &c)) == 1) {
*ptr++ = c;
if (c == '\n')
break; /* newline is stored, like fgets() */
} else if (rc == 0) {
*ptr = 0;
return (n - 1); /* EOF, n - 1 bytes were read */
} else
return (-1); /* error, errno set by read() */
}
*ptr = 0; /* null terminate like fgets() */
return (n);
}
ssize_t Readline(int fd, void *ptr, size_t maxlen)
{
ssize_t n;
if ((n = readline(fd, ptr, maxlen)) < 0)
err_sys("readline error");
return (n);
}
void str_cli(FILE * fp, int sockfd)
{
char sendline[MAXLINE], recvline[MAXLINE];
while (Fgets(sendline, MAXLINE, fp) != NULL) {
Writen(sockfd, sendline, strlen(sendline));
if (Readline(sockfd, recvline, MAXLINE) == 0)
err_quit("str_cli: server terminated prematurely");
Fputs(recvline, stdout);
}
}
int main(int argc, char **argv)
{
int sockfd;
struct sockaddr_in servaddr;
if (argc != 2)
err_quit("usage: tcpcli <IPaddress>");
sockfd = Socket(AF_INET, SOCK_STREAM, 0);
bzero(&servaddr, sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_port = htons(SERV_PORT);
Inet_pton(AF_INET, argv[1], &servaddr.sin_addr);
Connect(sockfd, (SA *) & servaddr, sizeof(servaddr));
str_cli(stdin, sockfd); /* do it all */
exit(0);
}
5.10 wait和waitpid函数
//带上信号处理函数的server
#define _POSIX_SOURCE
#include <strings.h>
#include <signal.h>
#include <sys/types.h> /* basic system data types */
#include <sys/socket.h> /* basic socket definitions */
#include <netinet/in.h> /* sockaddr_in{} and other Internet defns */
#include <stdarg.h> /* ANSI C header file */
#include <syslog.h> /* for syslog() */
#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/wait.h>
int daemon_proc; /* set nonzero by daemon_init() */
#define SA struct sockaddr
#define MAXLINE 4096 /* max text line length */
#define SERV_PORT 9877 /* TCP and UDP */
#define LISTENQ 1024 /* 2nd argument to listen() */
typedef void Sigfunc(int); /* for signal handlers */
void err_doit(int errnoflag, int level, const char *fmt, va_list ap)
{
int errno_save, n;
char buf[MAXLINE + 1];
errno_save = errno; /* value caller might want printed */
#ifdef HAVE_VSNPRINTF
vsnprintf(buf, MAXLINE, fmt, ap); /* safe */
#else
vsprintf(buf, fmt, ap); /* not safe */
#endif
n = strlen(buf);
if (errnoflag)
snprintf(buf + n, MAXLINE - n, ": %s", strerror(errno_save));
strcat(buf, "\n");
if (daemon_proc) {
syslog(level, "%s", buf);
} else {
fflush(stdout); /* in case stdout and stderr are the same */
fputs(buf, stderr);
fflush(stderr);
}
return;
}
void err_sys(const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
err_doit(1, LOG_ERR, 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 Bind(int fd, const struct sockaddr *sa, socklen_t salen)
{
if (bind(fd, sa, salen) < 0)
err_sys("bind 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");
}
pid_t Fork(void)
{
pid_t pid;
if ((pid = fork()) == -1)
err_sys("fork error");
return (pid);
}
void Close(int fd)
{
if (close(fd) == -1)
err_sys("close error");
}
ssize_t /* Write "n" bytes to a descriptor. */
writen(int fd, const void *vptr, size_t n)
{
size_t nleft;
ssize_t nwritten;
const char *ptr;
ptr = (const char *)vptr;
nleft = n;
while (nleft > 0) {
if ((nwritten = write(fd, ptr, nleft)) <= 0) {
if (nwritten < 0 && errno == EINTR)
nwritten = 0; /* and call write() again */
else
return (-1); /* error */
}
nleft -= nwritten;
ptr += nwritten;
}
return (n);
}
void Writen(int fd, void *ptr, int nbytes)
{
if (writen(fd, ptr, nbytes) != nbytes)
err_sys("writen error");
}
void str_echo(int sockfd)
{
ssize_t n;
char buf[MAXLINE];
again:
while ((n = read(sockfd, buf, MAXLINE)) > 0)
Writen(sockfd, buf, n);
if (n < 0 && errno == EINTR)
goto again;
else if (n < 0)
err_sys("str_echo: read error");
}
void sig_chld(int signo)
{
pid_t pid;
int stat;
while ((pid = waitpid(-1, &stat, WNOHANG)) > 0)
printf("child %d terminated\n", pid);
return;
}
Sigfunc *signal(int signo, Sigfunc * func)
{
struct sigaction act, oact;
act.sa_handler = func;
sigemptyset(&act.sa_mask);
act.sa_flags = 0;
if (signo == SIGALRM) {
#ifdef SA_INTERRUPT
act.sa_flags |= SA_INTERRUPT; /* SunOS 4.x */
#endif
} else {
#ifdef SA_RESTART
act.sa_flags |= SA_RESTART; /* SVR4, 44BSD */
#endif
}
if (sigaction(signo, &act, &oact) < 0)
return (SIG_ERR);
return (oact.sa_handler);
}
Sigfunc *Signal(int signo, Sigfunc * func)
{ /* for our signal() function */
Sigfunc *sigfunc;
if ((sigfunc = signal(signo, func)) == SIG_ERR)
err_sys("signal error");
return (sigfunc);
}
int main()
{
int listenfd, connfd;
pid_t childpid;
socklen_t clilen;
struct sockaddr_in cliaddr, servaddr;
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(SERV_PORT);
Bind(listenfd, (SA *) & servaddr, sizeof(servaddr));
Listen(listenfd, LISTENQ);
Signal(SIGCHLD, sig_chld); /* must call waitpid() */
for (;;) {
clilen = sizeof(cliaddr);
if ((connfd = accept(listenfd, (SA *) & cliaddr, &clilen)) < 0) {
if (errno == EINTR)
continue; /* back to for() */
else
err_sys("accept error");
}
if ((childpid = Fork()) == 0) { /* child process */
Close(listenfd); /* close listening socket */
str_echo(connfd); /* process the request */
exit(0);
}
Close(connfd); /* parent closes connected socket */
}
}
