更多网络程序设计的文章见:目录
select
int select(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, struct timeval *timeout)
int nfd
: 读写异常集合中的文件描述的最大值fd_set *readfds
: 读集合fd_set *writefds
: 写集合fd_set *exceptfds
: 异常集合struct timeval *timeout
: 超时结构体
读、写、异常事件发生条件
- 可读
- 套接口缓冲区 有数据可读
- 连接的读一半关闭,即接收到FIN段,读操作将返回0
- 如果是监听套接口,已完成连接队列不为空时
- 套接口上发生了一个错误待处理,错误可以通过getsockopt指定SO_ERROR选项来获取
- 可写
- 套接口发送缓冲区有空间容纳数据
- 连接的写一半关闭,即收到RST段之后,再次调用write操作
- 套接口上发生了一个错误待处理,错误可以通过getsockopt指定SO_ERROR选项来获取
- 异常
- 套接口存在带外数据
用select改进程序
- echosrv.c
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <signal.h>
#include <sys/wait.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#define ERR_EXIT(m) \
do\
{\
perror(m);\
exit(EXIT_FAILURE);\
}while (0)
ssize_t readn(int fd, void *buf, size_t count)
{
size_t nleft = count;
ssize_t nread;
char *bufp = (char*)buf;
while(nleft > 0)
{
if((nread = read(fd, bufp, nleft)) < 0)
{
if(errno == EINTR)
continue;
return -1;
}
else if(nread == 0)
return count - nleft;
bufp += nread;
nleft -= nread;
}
return count;
}
ssize_t writen(int fd, const void *buf, size_t count)
{
size_t nleft = count;
ssize_t nwritten;
char *bufp = (char*)buf;
while(nleft > 0)
{
if((nwritten = write(fd, bufp, nleft)) < 0)
{
if(errno == EINTR)
continue;
return -1;
}
else if(nwritten == 0)
continue;
bufp += nwritten;
nleft -= nwritten;
}
return count;
}
ssize_t recv_peek(int sockfd, void *buf, size_t len)//与原型相比去掉了flags
{//可以从套接口接收数据,可以指定不将缓冲区数据移除
while(1)
{
int ret = recv(sockfd, buf, len, MSG_PEEK);
if(ret == -1 && errno == EINTR)
continue;
return ret;
}
}
//暗含读取方法,标准是一个个读取,但效率太低,因此用偷窥的方法
//recv_peek不可重入
ssize_t readline(int sockfd, void *buf, size_t maxline)
{
int ret;
int nread;
char *bufp = buf;
int nleft = maxline;
while(1)
{
ret = recv_peek(sockfd, bufp, nleft);
if(ret < 0)
return ret;
else if(ret == 0)
return ret;//对方关闭了套接口
nread = ret;
int i;
for(i = 0; i < nread; i++)//最简单情况,有一条消息,我们读走
{
if(bufp[i] == '\n')
{
ret = readn(sockfd, bufp, i + 1);
if(ret != i+1)
exit(EXIT_FAILURE);
return ret;
}
}
if(nread > nleft)
exit(EXIT_FAILURE);
nleft -= nread;
ret = readn(sockfd, bufp, nread);
if(ret != nread)
exit(EXIT_FAILURE);
bufp += nread;
}
return -1;
}
void echo_srv(int conn)
{
char recvbuf[1024];
while(1)
{
memset(recvbuf, 0, sizeof(recvbuf));
int ret = readline(conn, recvbuf, 1024);
if(ret == -1)
ERR_EXIT("readline");
if(ret == 0)
{
printf("client close\n");
break;
}
fputs(recvbuf, stdout);
writen(conn, recvbuf, strlen(recvbuf));
}
}
void handle_sigchld(int sig)
{
/* wait(NULL);*/
while(waitpid(-1, NULL, WNOHANG) > 0);//处理多个进程
}
int main(void)
{
//signal(SIGCHLD, SIG_IGN);//解决僵尸进程问题
//另一种方法(推荐,加上waitpid的调用)
signal(SIGCHLD, handle_sigchld);
int listenfd;
if((listenfd = socket(PF_INET,SOCK_STREAM,IPPROTO_TCP))<0)//创建套接字小于0表示失败
/* if((listenfd = socket(PF_INET,SOCK_STREAM,0))<0);*///让内核自己选定协议
ERR_EXIT("socket");
struct sockaddr_in servaddr;
memset(&servaddr,0,sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_port = htons(5188);
servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
//servaddr.sin_addr.s_addr = inet_addr("127.0.0.1");
//inet_aton("10.18.95.29",&servaddr.sin_addr);
int on = 1;
if(setsockopt(listenfd,SOL_SOCKET,SO_REUSEADDR,&on,sizeof(on))<0)
ERR_EXIT("setsockopt");
if(bind(listenfd,(struct sockaddr*)&servaddr,sizeof(servaddr))<0)
ERR_EXIT("bind");
if(listen(listenfd,SOMAXCONN)<0)
ERR_EXIT("listen");
struct sockaddr_in peeraddr;
socklen_t peerlen;
int conn;
/*
pid_t pid;
while(1)
{
if((conn = accept(listenfd,(struct sockaddr*)&peeraddr,&peerlen)) < 0)
ERR_EXIT("accept");
printf("ip=%s,port=%d\n",inet_ntoa(peeraddr.sin_addr),ntohs(peeraddr.sin_port));
pid = fork();
if(pid == -1)
ERR_EXIT("fork");
if(pid == 0)
{
close(listenfd);
echo_srv(conn);
exit(EXIT_SUCCESS);
}
else
close(conn);
}
*/
int i;
int client[FD_SETSIZE];
int maxi = 0;//最大空闲位置
for(i = 0; i < FD_SETSIZE; i++)
{
client[i] = -1;
}
int nready;
int maxfd = listenfd;
fd_set rset;
fd_set allset;
FD_ZERO(&rset);
FD_ZERO(&allset);
FD_SET(listenfd, &allset);
while(1)
{
rset = allset;
nready = select(maxfd+1, &rset, NULL, NULL, NULL);
if(nready == -1)
{
if(errno == EINTR)
continue;
ERR_EXIT("select");
}
if(nready == 0)
continue;
if(FD_ISSET(listenfd, &rset))
{
peerlen = sizeof(peeraddr);
conn = accept(listenfd, (struct sockaddr*)&peeraddr, &peerlen);
if(conn == -1)
ERR_EXIT("accept");
for(i = 0; i < FD_SETSIZE; i++)
{
if(client[i] < 0)
{
client[i] = conn;
if(i > maxi)
maxi = i;
break;
}
}
if(i == FD_SETSIZE)
{
fprintf(stderr, "too many client\n");
exit(EXIT_FAILURE);
}
printf("ip=%s,port=%d\n",inet_ntoa(peeraddr.sin_addr),ntohs(peeraddr.sin_port));
FD_SET(conn, &allset);
if(conn > maxfd)
maxfd = conn;
if(--nready <= 0)
continue;
}
for(i = 0; i <= maxi; i++)//遍历到maxi,稍微提高了一点效率
{
conn = client[i];
if(conn == -1)
continue;
if(FD_ISSET(conn, &rset))
{
char recvbuf[1024] = {0};
int ret = readline(conn, recvbuf, 1024);
if(ret == -1)
ERR_EXIT("readline");
if(ret == 0)
{
printf("client close\n");
FD_CLR(conn, &allset);
client[i] = -1;
}
fputs(recvbuf, stdout);
writen(conn, recvbuf, strlen(recvbuf));
if(--nready <= 0)
break;
}
}
}
return 0;
}
- echocli.c
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <signal.h>
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#define ERR_EXIT(m) \
do \
{ \
perror(m); \
exit(EXIT_FAILURE); \
}while(0)
ssize_t readn(int fd, void *buf, size_t count)
{
size_t nleft = count;
ssize_t nread;
char *bufp = (char*)buf;
while(nleft > 0)
{
if((nread = read(fd, bufp, nleft)) < 0)
{
if(errno == EINTR)
continue;
return -1;
}
else if(nread == 0)
return count - nleft;
bufp += nread;
nleft -= nread;
}
return count;
}
ssize_t writen(int fd, const void *buf, size_t count)
{
size_t nleft = count;
ssize_t nwritten;
char *bufp = (char*)buf;
while(nleft > 0)
{
if((nwritten = write(fd, bufp, nleft)) < 0)
{
if(errno == EINTR)
continue;
return -1;
}
else if(nwritten == 0)
continue;
bufp += nwritten;
nleft -= nwritten;
}
return count;
}
ssize_t recv_peek(int sockfd, void *buf, size_t len)
{
while(1)
{
int ret = recv(sockfd, buf, len, MSG_PEEK);
if(ret == -1 && errno == EINTR)
continue;
return ret;
}
}
ssize_t readline(int sockfd, void *buf, size_t maxline)
{
int ret;
int nread;
char *bufp = buf;
int nleft = maxline;
while(1)
{
ret = recv_peek(sockfd, bufp, nleft);
if(ret < 0)
return ret;
else if(ret == 0)
return ret;//对方关闭了套接口
nread = ret;
int i;
for(i = 0; i < nread; i++)
{
if(bufp[i] == '\n')
{
ret = readn(sockfd, bufp, i + 1);
if(ret != i+1)
exit(EXIT_FAILURE);
return ret;
}
}
if(nread > nleft)
exit(EXIT_FAILURE);
nleft -= nread;
ret = readn(sockfd, bufp, nread);
if(ret != nread)
exit(EXIT_FAILURE);
bufp += nread;
}
return -1;
}
void echo_cli(int sock)
{
/*
char sendbuf[1024] = {0};
char recvbuf[1024] = {0};
while(fgets(sendbuf, sizeof(sendbuf), stdin) != NULL)
{
writen(sock, sendbuf, strlen(sendbuf));
int ret = readline(sock, &recvbuf, sizeof(recvbuf));
if(ret == -1)
ERR_EXIT("readline");
else if(ret == 0)
{
printf("client_close\n");
break;
}
fputs(recvbuf, stdout);
memset(sendbuf, 0, sizeof(sendbuf));
memset(recvbuf, 0, sizeof(recvbuf));
}
close(sock);
*/
fd_set rset;
FD_ZERO(&rset);
int nready;
int maxfd;
int fd_stdin = fileno(stdin);
if(fd_stdin > sock)
maxfd = fd_stdin;
else
maxfd = sock;
char sendbuf[1024] = {0};
char recvbuf[1024] = {0};
while(1)
{
FD_SET(fd_stdin, &rset);
FD_SET(sock, &rset);
nready = select(maxfd+1, &rset, NULL, NULL, NULL);
if(nready == -1)
ERR_EXIT("select");
if(nready == 0)
continue;
if(FD_ISSET(sock, &rset))
{
int ret = readline(sock, &recvbuf, sizeof(recvbuf));
if(ret == -1)
ERR_EXIT("readline");
else if(ret == 0)
{
printf("server close\n");
break;
}
fputs(recvbuf, stdout);
memset(recvbuf, 0, sizeof(recvbuf));
}
if(FD_ISSET(fd_stdin, &rset))
{
if(fgets(sendbuf, sizeof(sendbuf), stdin) == NULL)
break;
writen(sock, sendbuf, strlen(sendbuf));
memset(sendbuf, 0, sizeof(sendbuf));
}
}
close(sock);
}
void handle_sigpipe(int sig)
{
printf("recv a sig=%d\n", sig);
}
int main(void)
{
/*signal(SIGPIPE, handle_sigpipe);*/
signal(SIGPIPE, SIG_IGN);
int sock;
if((sock = socket(PF_INET,SOCK_STREAM,IPPROTO_TCP)) < 0)
{
ERR_EXIT("socket");
}
struct sockaddr_in servaddr;
memset(&servaddr,0,sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_port = htons(5188);
servaddr.sin_addr.s_addr = inet_addr("127.0.0.1");
if(connect(sock,(struct sockaddr*)&servaddr,sizeof(servaddr)) < 0)
{
ERR_EXIT("connect");
}
struct sockaddr_in localaddr;
socklen_t addrlen = sizeof(localaddr);
if(getsockname(sock, (struct sockaddr*)&localaddr, &addrlen) < 0)
ERR_EXIT("getsockname");
printf("ip=%s,port=%d\n", inet_ntoa(localaddr.sin_addr),ntohs(localaddr.sin_port));
echo_cli(sock);
return 0;
}