IO 复用

来源：互联网发布：linux killproc 编辑：程序博客网时间：2024/05/16 14:07

I/O复用典型的场景

1）客户处理多个描述符时
2）如果TCP服务器既要处理监听套接字，又要处理已连接套接字。
3）一个服务器既要处理UDP又要处理TCP时
4）一个服务器要处理多个服务或者协议时

I/O模型

1）阻塞式
2)非阻塞式
3）IO复用 select poll等
4)信号驱动I/O
5)异步I/O

相比较每个客户端起进程select 模型显然更大些，省资源，方便管理。

服务端

#include <stdio.h>#include <sys/types.h>          /* See NOTES */#include <sys/socket.h>#include <arpa/inet.h>#include <unistd.h>#include <string.h>#include <sys/select.h>#define max(x,y) ((x) > (y) ? (x) : (y))void str_cli(FILE *fp, int sockfd){    fd_set rset;    int maxfdp1, stdineof;    char buf[1024];    int n;    stdineof = 0;    FD_ZERO(&rset);    for( ; ; )    {        if(stdineof == 0)        {            FD_SET(fileno(fp), &rset);        }        FD_SET(sockfd, &rset);        maxfdp1 = max(fileno(fp), sockfd) + 1;        select(maxfdp1, &rset, NULL, NULL, NULL);        if(FD_ISSET(sockfd,&rset))        {            if( (n == read(sockfd, buf, 1024)) ==0)            {                if(stdineof == 1) return;                else                    printf("str_cli: server terminated prematurely \n");            }            write(fileno(stdout), buf, n);        }        if(FD_ISSET(fileno(fp),&rset))        {            if( (n == read(fileno(fp), buf, 1024)) ==0)            {                stdineof =1;                shutdown(sockfd, SHUT_WR);                FD_CLR(fileno(fp), &rset);                continue;            }            write(sockfd, buf, n);        }    }}int main(int argc , char** argv){    int sockfd;    struct sockaddr_in seraddr;    if(argc !=2)    {        printf("argc error\r\n");    }    if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0)    {        printf("socket error\r\n");    }    bzero(&seraddr, sizeof(seraddr));    seraddr.sin_family = AF_INET;    seraddr.sin_port = htons(13000);    if((inet_pton(AF_INET, argv[1], &seraddr.sin_addr)) < 0)    {        printf("inet_pton error\r\n");    }    if(connect(sockfd, (struct sockaddr*)&seraddr, sizeof(seraddr)) < 0)    {        printf("connect error\r\n");    }    str_cli(stdin, sockfd);    return 0;}

客户端

#include <stdio.h>#include <sys/types.h>          /* See NOTES */#include <sys/socket.h>#include <arpa/inet.h>#include <unistd.h>#include <string.h>#include <sys/select.h>#define max(x,y) ((x)>(y)?(x):(y))void str_cli(FILE *fp, int sockfd){    fd_set rset;    int maxfdp1, stdineof;    char buf[1024];    int n;    stdineof = 0;    FD_ZERO(&rset);    for( ; ; )    {        if(stdineof == 0)        {            FD_SET(fileno(fp), &rset);        }        FD_SET(sockfd, &rset);        maxfdp1 = max(fileno(fp), sockfd) + 1;        select(maxfdp1, &rset, NULL, NULL, NULL);        if(FD_ISSET(sockfd,&rset))        {            if( (n == read(sockfd, buf, 1024)) ==0)            {                if(stdineof == 1) return;                else                    printf("str_cli: server terminated prematurely \n");            }            write(fileno(stdout), buf, n);        }        if(FD_ISSET(fileno(fp),&rset))        {            if( (n = read(fileno(fp), buf, 1024)) ==0)            {                stdineof =1;                shutdown(sockfd, SHUT_WR);                FD_CLR(fileno(fp), &rset);                continue;            }            printf("write\r\n");            write(sockfd, buf, n);        }    }}int main(int argc , char** argv){    int sockfd;    struct sockaddr_in seraddr;    if(argc !=2)    {        printf("argc error\r\n");    }    if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0)    {        printf("socket error\r\n");    }    bzero(&seraddr, sizeof(seraddr));    seraddr.sin_family = AF_INET;    seraddr.sin_port = htons(13000);    if((inet_pton(AF_INET, argv[1], &seraddr.sin_addr)) < 0)    {        printf("inet_pton error\r\n");    }    if(connect(sockfd, (struct sockaddr*)&seraddr, sizeof(seraddr)) < 0)    {        printf("connect error\r\n");    }    str_cli(stdin, sockfd);    return 0;}

遇到的问题

判断语句写错

if( (n == read(fileno(fp), buf, 1024)) ==0)
if(FD_SET(fileno(fp),&rset))

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