第14章 高级I/O函数
14.2 套接字超时
14.2.1 使用SIGALRM 为连接设置超时
#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>
#include <signal.h>
#define MAXLINE 4096 /* max text line length */
#define SA struct sockaddr
typedef void Sigfunc(int); /* for signal handlers */
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);
}
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);
}
void err_msg(const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
err_doit(0, fmt, ap);
va_end(ap);
return;
}
void connect_alarm(int signo)
{
printf("time out\n");
return; /* just interrupt the connect() */
}
int connect_timeo(int sockfd, const SA * saptr, socklen_t salen, int nsec)
{
Sigfunc *sigfunc;
int n;
sigfunc = Signal(SIGALRM, connect_alarm);
if (alarm(nsec) != 0)
err_msg("connect_timeo: alarm was already set");
if ((n = connect(sockfd, saptr, salen)) < 0) {
close(sockfd);
if (errno == EINTR)
errno = ETIMEDOUT;
}
alarm(0); /* turn off the alarm */
Signal(SIGALRM, sigfunc); /* restore previous signal handler */
return (n);
}
void Connect_timeo(int fd, const SA * sa, socklen_t salen, int sec)
{
if (connect_timeo(fd, sa, salen, sec) < 0)
err_sys("connect_timeo error");
}
int main(int argc, char **argv)
{
int sockfd;
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]);
Connect_timeo(sockfd, (SA *) & servaddr, sizeof(servaddr), 5);
exit(0);
}
14.2.2 使用SIGALRM 为recvfrom设置超时
#include <netinet/in.h> /* sockaddr_in{} and other Internet defns */
#include <strings.h>
#include <stdarg.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <arpa/inet.h>
#include <signal.h>
#include <unistd.h>
#define MAXLINE 4096 /* max text line length */
#define SERV_PORT 9877 /* TCP and UDP */
#define SA struct sockaddr
typedef void Sigfunc(int); /* for signal handlers */
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 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 */
}
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);
}
ssize_t Recvfrom(int fd, void *ptr, size_t nbytes, int flags,
struct sockaddr * sa, socklen_t * salenptr)
{
ssize_t n;
if ((n = recvfrom(fd, ptr, nbytes, flags, sa, salenptr)) < 0)
err_sys("recvfrom error");
return (n);
}
void Sendto(int fd, const void *ptr, size_t nbytes, int flags,
const struct sockaddr *sa, socklen_t salen)
{
if (sendto(fd, ptr, nbytes, flags, sa, salen) != (ssize_t) nbytes)
err_sys("sendto error");
}
void Fputs(const char *ptr, FILE * stream)
{
if (fputs(ptr, stream) == EOF)
err_sys("fputs error");
}
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);
}
void sig_alrm(int signo)
{
printf("time out\n");
return; /* just interrupt the recvfrom() */
}
void dg_cli(FILE * fp, int sockfd, const SA * pservaddr, socklen_t servlen)
{
int n;
char sendline[MAXLINE], recvline[MAXLINE + 1];
Signal(SIGALRM, sig_alrm);
while (Fgets(sendline, MAXLINE, fp) != NULL) {
Sendto(sockfd, sendline, strlen(sendline), 0, pservaddr,
servlen);
alarm(5);
if ((n =
recvfrom(sockfd, recvline, MAXLINE, 0, NULL, NULL)) < 0) {
if (errno == EINTR)
fprintf(stderr, "socket timeout\n");
else
err_sys("recvfrom error");
} else {
alarm(0);
recvline[n] = 0; /* null terminate */
Fputs(recvline, stdout);
}
}
}
int main(int argc, char **argv)
{
int sockfd;
struct sockaddr_in servaddr;
if (argc != 2)
err_quit("usage: udpcli <IPaddress>");
bzero(&servaddr, sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_port = htons(SERV_PORT);
Inet_pton(AF_INET, argv[1], &servaddr.sin_addr);
sockfd = Socket(AF_INET, SOCK_DGRAM, 0);
dg_cli(stdin, sockfd, (SA *) & servaddr, sizeof(servaddr));
exit(0);
}
14.2.3 使用select 为recvfrom设置超时
#include <netinet/in.h> /* sockaddr_in{} and other Internet defns */
#include <strings.h>
#include <sys/select.h>
#include <stdarg.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <arpa/inet.h>
#define MAXLINE 4096 /* max text line length */
#define SERV_PORT 9877 /* TCP and UDP */
#define SA struct sockaddr
typedef void Sigfunc(int); /* for signal handlers */
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 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 */
}
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);
}
ssize_t Recvfrom(int fd, void *ptr, size_t nbytes, int flags,
struct sockaddr * sa, socklen_t * salenptr)
{
ssize_t n;
if ((n = recvfrom(fd, ptr, nbytes, flags, sa, salenptr)) < 0)
err_sys("recvfrom error");
return (n);
}
void Sendto(int fd, const void *ptr, size_t nbytes, int flags,
const struct sockaddr *sa, socklen_t salen)
{
if (sendto(fd, ptr, nbytes, flags, sa, salen) != (ssize_t) nbytes)
err_sys("sendto error");
}
void Fputs(const char *ptr, FILE * stream)
{
if (fputs(ptr, stream) == EOF)
err_sys("fputs error");
}
int readable_timeo(int fd, int sec)
{
fd_set rset;
struct timeval tv;
FD_ZERO(&rset);
FD_SET(fd, &rset);
tv.tv_sec = sec;
tv.tv_usec = 0;
return (select(fd + 1, &rset, NULL, NULL, &tv));
/* 4> 0 if descriptor is readable */
}
int Readable_timeo(int fd, int sec)
{
int n;
if ((n = readable_timeo(fd, sec)) < 0)
err_sys("readable_timeo error");
return (n);
}
void dg_cli(FILE * fp, int sockfd, const SA * pservaddr, socklen_t servlen)
{
int n;
char sendline[MAXLINE], recvline[MAXLINE + 1];
while (Fgets(sendline, MAXLINE, fp) != NULL) {
Sendto(sockfd, sendline, strlen(sendline), 0, pservaddr,
servlen);
if (Readable_timeo(sockfd, 5) == 0) {
fprintf(stderr, "socket timeout\n");
} else {
n = Recvfrom(sockfd, recvline, MAXLINE, 0, NULL, NULL);
recvline[n] = 0; /* null terminate */
Fputs(recvline, stdout);
}
}
}
int main(int argc, char **argv)
{
int sockfd;
struct sockaddr_in servaddr;
if (argc != 2)
err_quit("usage: udpcli <IPaddress>");
bzero(&servaddr, sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_port = htons(SERV_PORT);
Inet_pton(AF_INET, argv[1], &servaddr.sin_addr);
sockfd = Socket(AF_INET, SOCK_DGRAM, 0);
dg_cli(stdin, sockfd, (SA *) & servaddr, sizeof(servaddr));
exit(0);
}
14.2.4 使用 SO_RCVTIMEO 为recvfrom 设置超时
#define __need_timeval
#include <strings.h>
#include <time.h>
#include <netinet/in.h> /* sockaddr_in{} and other Internet defns */
#include <stdarg.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <arpa/inet.h>
#define MAXLINE 4096 /* max text line length */
#define SERV_PORT 9877 /* TCP and UDP */
#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 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 */
}
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);
}
ssize_t Recvfrom(int fd, void *ptr, size_t nbytes, int flags,
struct sockaddr * sa, socklen_t * salenptr)
{
ssize_t n;
if ((n = recvfrom(fd, ptr, nbytes, flags, sa, salenptr)) < 0)
err_sys("recvfrom error");
return (n);
}
void Sendto(int fd, const void *ptr, size_t nbytes, int flags,
const struct sockaddr *sa, socklen_t salen)
{
if (sendto(fd, ptr, nbytes, flags, sa, salen) != (ssize_t) nbytes)
err_sys("sendto error");
}
void Fputs(const char *ptr, FILE * stream)
{
if (fputs(ptr, stream) == EOF)
err_sys("fputs error");
}
void Setsockopt(int fd, int level, int optname, const void *optval,
socklen_t optlen)
{
if (setsockopt(fd, level, optname, optval, optlen) < 0)
err_sys("setsockopt error");
}
void dg_cli(FILE * fp, int sockfd, const SA * pservaddr, socklen_t servlen)
{
int n;
char sendline[MAXLINE], recvline[MAXLINE + 1];
struct timeval tv;
tv.tv_sec = 5;
tv.tv_usec = 0;
Setsockopt(sockfd, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv));
while (Fgets(sendline, MAXLINE, fp) != NULL) {
Sendto(sockfd, sendline, strlen(sendline), 0, pservaddr,
servlen);
n = recvfrom(sockfd, recvline, MAXLINE, 0, NULL, NULL);
if (n < 0) {
if (errno == EWOULDBLOCK) {
fprintf(stderr, "socket timeout\n");
continue;
} else
err_sys("recvfrom error");
}
recvline[n] = 0; /* null terminate */
Fputs(recvline, stdout);
}
}
int main(int argc, char **argv)
{
int sockfd;
struct sockaddr_in servaddr;
if (argc != 2)
err_quit("usage: udpcli <IPaddress>");
bzero(&servaddr, sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_port = htons(SERV_PORT);
Inet_pton(AF_INET, argv[1], &servaddr.sin_addr);
sockfd = Socket(AF_INET, SOCK_DGRAM, 0);
dg_cli(stdin, sockfd, (SA *) & servaddr, sizeof(servaddr));
exit(0);
}
