服务器与多个客户端通信

使用多路复用实现一个服务器与多个客户端的通信：代码范例：
服务器：
#include<stdio.h>
#include<netinet/in.h>
#include<stdlib.h>
#include<string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include<pthread.h>
#include<strings.h>

void send1(int *a)
{
    int i;
    char buf[20];
    bzero(buf,20);
    fgets(buf,20,stdin);
    for(i=0;i<12;i++)
    {    if(a[i] !=0)
        send(a[i],buf,20,0);
    }
}
int main()
{
    int fds[12]={0};
    int maxfd = -1;
    int socketfd = socket(PF_INET,SOCK_STREAM,0);
    if(socketfd>maxfd)
        maxfd = socketfd;
    struct sockaddr_in saddr;
    memset(&saddr,0,sizeof(saddr));
    saddr.sin_family = PF_INET;
    saddr.sin_port = htons(6000);
    saddr.sin_addr.s_addr = inet_addr("192.168.1.46");
    int newsocketfd;
    int n = 1;
    setsockopt(socketfd, SOL_SOCKET, SO_REUSEADDR, &n, sizeof(int));
    if(bind(socketfd,(struct sockaddr*)&saddr,sizeof(struct sockaddr_in))<0)
        perror("bind() error!\n");

    if(listen(socketfd,5)<0)
        perror("listen() error!\n");
    struct sockaddr_in caddr;
    int s = sizeof(struct sockaddr);
//    newsocketfd = accept(socketfd,(struct sockaddr*)&caddr,&s);
    fd_set fd;
    FD_ZERO(&fd);
    int ret;
    char buf[20],buf1[20];
    int i;
    int rsize;
    while(1)
    {
        FD_ZERO(&fd);
        FD_SET(0,&fd);
        FD_SET(socketfd,&fd);
        for(i=0;i<12;i++)
        {
    //    printf("--------------\n");
            if(fds[i]!=0)
            FD_SET(fds[i],&fd);
        }
        ret = select(maxfd+1,&fd,NULL,NULL,NULL);
        if(ret<0)
        {
            perror("select() error!\n");
            break;
        }
        else if(ret ==0)
        {
            continue;
        }
        else
        {
            if(FD_ISSET(socketfd,&fd))
            {
                newsocketfd = accept(socketfd,(struct sockaddr*)&caddr,&s);
            if(newsocketfd>maxfd)
            {
    //    printf("--------------\n");
                maxfd = newsocketfd;
                for(i=0;i<12;i++)
                {
                    if(fds[i]==0)
                    {
                        fds[i] = newsocketfd;
                        break;
                    }
                }

            }
            continue;
            }
//            printf("helo\n");
            for(i=0;i<12;i++)
            {
                if(fds[i] !=0 && FD_ISSET(fds[i],&fd))
                {
                    bzero(buf1,20);
                    if(recv(fds[i],buf1,20,0)==0)
                    {
                        close(fds[i]);
                        fds[i] = 0;
                    }
                    printf("%s",buf1);
                }
            }
                if(FD_ISSET(0,&fd))
                {
                    send1(fds);
                }
    }
    }
    close(socketfd);
    close(newsocketfd);

}
客户端：
#include<stdio.h>
#include<pthread.h>
#include<netinet/in.h>
#include<stdlib.h>
#include<string.h>
#include<strings.h>
#include<sys/types.h>
#include<sys/socket.h>
int main()
{
    int socketfd,ret;
    fd_set fd;
    FD_ZERO(&fd);
    FD_SET(0,&fd);

    socketfd = socket(PF_INET,SOCK_STREAM,0);
    FD_SET(socketfd,&fd);
    ret = select(socketfd+1,&fd,NULL,NULL,NULL);
    struct sockaddr_in saddr;
    memset(&saddr,0,sizeof(saddr));
    saddr.sin_family = PF_INET;
    saddr.sin_port = htons(6000);
    saddr.sin_addr.s_addr = inet_addr("192.168.1.46");

    if(connect(socketfd,(struct sockaddr *)&saddr,sizeof(struct sockaddr))<0)

        perror("connect() error!\n");
//    pthread_t pthreadid;
//    pthread_create(&pthreadid,NULL,func,NULL);
    char buf[20],buf1[20];
    while(1)
    {
        bzero(buf,20);
        bzero(buf1,20);

    FD_SET(0,&fd);
    FD_SET(socketfd,&fd);
    ret = select(socketfd+1,&fd,NULL,NULL,NULL);
            if(FD_ISSET(socketfd,&fd))
            {
            if(recv(socketfd,buf1,sizeof(buf1),0)<0)
                perror("recv() error!\n");
                printf("%s",buf1);
                continue;
            }
            if(FD_ISSET(0,&fd))
            {
            fgets(buf,20,stdin);
            if(send(socketfd,buf,strlen(buf),0)<0)
            perror("send() error!\n");
            continue;
            }    

        }