并发服务器

#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <time.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
 
const int maxline = 4096;
 
int main(int argc, char **argv) {
    int listenfd, connfd;
    socklen_t len;
    pid_t childpid;
    struct sockaddr_in servaddr, cliaddr;
    char buff[maxline], errbuff[maxline];
    time_t ticks;
 
    if((listenfd=socket(AF_INET, SOCK_STREAM, 0))<0) {
        strerror_r(errno, errbuff, maxline);
        fprintf(stderr, "socket error: %s\n", errbuff);
        exit(-1);
    }
     
    memset(&servaddr, 0, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port = htons(9999);
 
    if(bind(listenfd, (struct sockaddr *)&servaddr, sizeof(servaddr))<0) {
        strerror_r(errno, errbuff, maxline);
        fprintf(stderr, "bind error: %s\n", errbuff);
        exit(-1);
    }
 
    if(listen(listenfd, 1024)<0) {
        strerror_r(errno, errbuff, maxline);
        fprintf(stderr, "listen error: %s\n", errbuff);
        exit(-1);
    }
     
    for(;;) {
        len=sizeof(cliaddr);
        if((connfd=accept(listenfd, (struct sockaddr *)&cliaddr, &len))<0) {
            strerror_r(errno, errbuff, maxline);
            fprintf(stderr, "accept error: %s\n", errbuff);
            exit(-1);
        }
        printf("connection from %s, port %d\n", inet_ntop(AF_INET, &cliaddr.sin_addr, buff, sizeof(buff)), ntohs(cliaddr.sin_port));
        if((childpid=fork())<0) {
            strerror_r(errno, errbuff, maxline);
            fprintf(stderr, "fork error: %s\n", errbuff);
            exit(-1);
        } else if(childpid == 0) {
            printf("ppid: %d\n", getppid());
            if(close(listenfd)<0) {
                strerror_r(errno, errbuff, maxline);
                fprintf(stderr, "child pid close listenfd error: %s\n", errbuff);
                exit(-1);
            }
            ticks = time(NULL);
            snprintf(buff, sizeof(buff), "%.24s\r\n", ctime(&ticks));
            if(write(connfd, buff, strlen(buff)) != strlen(buff)) {
                strerror_r(errno, errbuff, maxline);
                fprintf(stderr, "write error: %s\n", errbuff);
                exit(-1);
            }
            exit(0);
        } else {
            printf("childpid: %d\n", childpid);
            if(close(connfd)<0) {
                strerror_r(errno, errbuff, maxline);
                fprintf(stderr, "parent pid close connfd error: %s\n", errbuff);
                exit(-1);
            }
        }
    }
    return 0;
}   