Linux基础——通过select实现简单的服务器与客户端

在这里，我们还是需要一个管道，只不过，我们只需这一个管道，即可知道，客户端有哪些上线、对话、下线等。

服务器端的实现代码如下:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <fcntl.h>
#include <sys/time.h>
#include <sys/select.h>
#include <errno.h>
#define ON 1
#define OFF 0
int errno;
typedef struct tag
{
    int id;
    int fd;
    int type;
}NODE;
int main(int argc, const char *argv[])
{
    if(mkfifo(argv[1], 0666) == -1)
    {
        printf("创建管道失败!!
");
        exit(1);
    }
    
    int fd;
    fd = open(argv[1], O_RDONLY);
    if(fd == -1)
    {
        printf("open error!!
");
        exit(1);
    }
    NODE list[1024];
    int i;
    for(i = 0; i< 1024; i ++)
    {
        list[i].id = 0;
        list[i].type = OFF;
        list[i].fd = 0;
    }
    fd_set readset, ready;
    FD_ZERO(&readset);
    FD_ZERO(&ready);
    FD_SET(fd, &readset);
    struct timeval tm;
    char buf[128];
    int ret;
    while(1)
    {
        ready = readset;
        tm.tv_sec = 0;
        tm.tv_usec = 1000;
        ret = select(fd + 1, &ready, NULL, NULL, &tm);
        if(ret == 0)
            continue;
        else if(ret == -1)
        {
            if(errno == EINTR)
                continue;
            break;
        }
        else
        {
            memset(buf, 0, 128);
            read(fd, buf, 128);
            if(strncmp(buf, "on", 2) == 0)
            {
                int sfd;
                char name[128];
                memset(name, 0, 128);
                sscanf(buf + 3, "%d", &sfd);
                printf(" %d is on !!
", sfd);
                sprintf(name, "%d.fifo", sfd);
                int index;
                for(index = 0; index < 1024; index ++)
                {
                    if(list[index].type == OFF)
                    {
                        list[index].id = sfd;
                        list[index].fd = open(name, O_WRONLY);
                        list[index].type = ON;
                        break;
                    }
                }
            }
            else if(strncmp(buf, "off", 3) == 0)
            {
                int sfd;
                sscanf(buf + 4, "%d", &sfd);
                printf("%d is off !!
", sfd);
                int index;
                for(index = 0; index <1024; index ++)
                {
                    if(list[index].id == sfd)
                    {
                        close(list[index].fd);
                        list[index].id = 0;
                        list[index].type = OFF;
                        break;
                    }
                }
            }
            else
            {
                int sfd;
                sscanf(buf + 5, "%d", &sfd);
                int index;
                for(index = 0; index < 1024; index ++)
                {
                    if(list[index].type == ON && list[index].id != sfd)
                        write(list[index].fd, buf, strlen(buf));
                }
            }
        }
    }
    close(fd);
    unlink(argv[1]);
    return 0;
}

在这里，当ret = -1时，我们需要判断errno是否由信号中断引起的，如果是由于人为的退出，那么程序将退出，

如果是由于信号中断，程序将再次连接信号，等待数据。

客户端的实现代码如下:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/select.h>
#include <fcntl.h>
int main(int argc, const char *argv[])
{
    char name[128];
    memset(name, 0, 128);
    sprintf(name, "%d.fifo", getpid());
    if(mkfifo(name, 0666) == -1)
    {
        printf("创建管道失败!!
");
        exit(1);
    }
    int fd;
    fd = open(argv[1], O_WRONLY);
    if(fd == -1)
    {
        printf("open error!!
");
        exit(1);
    }
    char buf[128];
    memset(buf, 0, 128);
    sprintf(buf,"on %d
",getpid());
    write(fd, buf, strlen(name));
    int sfd;
    sfd = open(name, O_RDONLY);
    if(sfd == -1)
    {
        printf("open error!!
");
        exit(1);
    }
    if(fork() == 0)
    {
        if(fork() == 0)
        {
            close(fd);
            while(memset(buf, 0, 128), read(sfd, buf, 128))
                printf(" >> %s
", buf);
            close(sfd);
            exit(1);
        }
        exit(1);
    }
    wait(NULL);
    close(sfd);
    while(memset(buf, 0, 128), fgets(buf, 128, stdin) != NULL)
    {
        char msg[128];
        memset(msg, 0, 128);
        sprintf(msg, "from %d: %s",getpid(), buf);
        write(fd, msg, strlen(msg));
    }
    memset(buf, 0, 128);
    sprintf(buf, "off %d
", getpid());
    write(fd, buf, strlen(buf));
    close(fd);
    unlink(name);
    return 0;
}