简单回射程序之处理accept返回EINTR错误的服务器程序版本

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <unistd.h>
#include <signal.h>
#include <sys/socket.h>

#define SERV_PORT 9999
#define MAXLINE 4096
#define LISTENQ 1024
#define SA struct sockaddr

typedef void Sigfunc(int);

void str_echo(int);
void sig_chld(int);
ssize_t writen(int, const void*, size_t);
Sigfunc *signal(int, Sigfunc*);

int main(int argc, char *argv[]) {
    int listenfd, connfd;
    pid_t childpid;
    socklen_t clilen;
    struct sockaddr_in cliaddr, servaddr;

    listenfd = socket(AF_INET, SOCK_STREAM, 0);

    bzero(&servaddr, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port = htons(SERV_PORT);

    bind(listenfd, (SA *)&servaddr, sizeof(servaddr));

    listen(listenfd, LISTENQ); 

    signal(SIGCHLD, sig_chld); /* Install signal processing function */

    for ( ; ; ) {
        clilen = sizeof(cliaddr);
    　　 if ( (connfd = accept(listenfd, (SA *)&cliaddr, &clilen)) < 0) {
        　　if (errno == EINTR) {
                  continue;
        　　} else {
            　   perror("accept");
                  return;
        　　}
        }

        if ( (childpid = fork()) == 0) { /* Generate child processes to handle foreign connections */
            close(listenfd);
            str_echo(connfd);
            exit(0);
        }
        close(connfd);
    }
    close(listenfd);
    exit(0);
}

void str_echo(int sockfd) {
    ssize_t n;
    char buf[MAXLINE];

    again:
    while ( (n = read(sockfd, buf, MAXLINE)) > 0) {
        writen(sockfd, buf, n);
        bzero(buf, sizeof(buf));
    }
    if (n < 0 && errno == EINTR) {
        goto again;
    } else if (n < 0) {
        perror("read");
    }
}