C语言 终止套接字服务器中的分叉进程

Question

我已经编写了一个基于套接字的多客户端服务器和一个客户端作为辅助，但我似乎无法摆脱分叉进程。每次我关闭客户端或输入退出命令时，进程似乎都没有关闭。当检查ps aux| grep server时，有一个失败的过程。我怎样才能摆脱它们，关闭分叉的假肢时我做错了什么。

服务器：

#include <stdio.h>
#include <stdlib.h>
#include <strings.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <time.h>
void error(char *msg)
{
    perror(msg);
    exit(1);
}
void doprocessing (int sock)
{
   int n;
   char buffer[5];
   time_t rawtime;
   char tim[22];
   char dat[20];
   char day[16];
   char yer[18];
   while(1)
   {
     bzero(buffer,5);
     n = read(sock,buffer,5);
     if (n < 0) error("ERROR reading from socket");
     printf("Got %.3s command.n",buffer);
     if (strcasecmp(buffer, "timn") == 0)
     {
        rawtime = time(NULL);
        strncpy(tim, "Current time: ", 14);
        strncpy(tim+14, (ctime(&rawtime))+11, 8);
        n = write(sock, tim, 22);
     }
     else if (strcasecmp(buffer, "datn") == 0)
     {
        rawtime = time(NULL);
        strncpy(dat, "Current date: ", 14);
        strncpy(dat+14, (ctime(&rawtime))+4, 6);
        n = write(sock, dat, 20);
     }
     else if (strcasecmp(buffer, "dayn") == 0)
     {
        rawtime = time(NULL);
        strncpy(day, "Current day: ", 13);
        strncpy(day+13, (ctime(&rawtime)), 3);
        n = write(sock, day, 16);
     }
     else if (strcasecmp(buffer, "yern") == 0)
     {
        rawtime = time(NULL);
        strncpy(yer, "Current year: ", 14);
        strncpy(yer+14, (ctime(&rawtime))+20, 4);
        n = write(sock, yer, 18);
     }
     else if (strcasecmp(buffer, "comn") == 0)
     {
        n = write(sock, "TIM - current timenDAT - Month and daynDAY - current weekdaynYER - YearnEXT - exit", 82);
     }
     else if (strcasecmp(buffer, "extn") == 0)
     {
        n = write(sock, "Exiting", 7);
        break;
     }
     else  n = write(sock, "Wrong command enter COM to see commands.",40);
     if (n < 0) error("ERROR writing to socket");}
   }
int main(int argc, char *argv[])
{
    int sockfd, newsockfd, portno, clilen, n;
    char buffer[256];
    struct sockaddr_in serv_addr, cli_addr;
    int pid;
    if (argc < 2)
    {
        fprintf(stderr, "ERROR, no port provided");
        exit(1);
    }
    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd < 0) error("ERROR opening socket");
    bzero((char *) &serv_addr, sizeof(serv_addr));
    portno = atoi(argv[1]);
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_port = htons(portno);
    serv_addr.sin_addr.s_addr = INADDR_ANY;
    if (bind(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0) error("ERROR on binding");
    listen(sockfd, 5);
    clilen = sizeof(cli_addr);
    while(1)
    {
         newsockfd = accept(sockfd, (struct sockaddr *) &cli_addr, &clilen);
         if (newsockfd < 0) error("ERROR on accept");

         pid = fork();
         if (pid < 0) error("ERROR on fork");
         if (pid == 0)
         {
             close(sockfd);
             doprocessing(newsockfd);
             exit(-1);
         }
         else close(newsockfd);
    }
    close(sockfd);
    return 0;
}

客户：

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h> 
void error(const char *msg)
{
    perror(msg);
    exit(0);
}
int main(int argc, char *argv[])
{
    int sockfd, portno, n;
    struct sockaddr_in serv_addr;
    struct hostent *server;
    char rbuffer[256];
    char sbuffer[256];
    if (argc < 3)
    {
       fprintf(stderr,"usage %s hostname portn", argv[0]);
       exit(0);
    }
    portno = atoi(argv[2]);
    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd < 0) error("ERROR opening socket");
    server = gethostbyname(argv[1]);
    if (server == NULL)
    {
        fprintf(stderr,"ERROR, no such hostn");
        exit(0);
    }
    bzero((char *) &serv_addr, sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;
    bcopy((char *)server->h_addr, (char *)&serv_addr.sin_addr.s_addr, server->h_length);
    serv_addr.sin_port = htons(portno);
    if (connect(sockfd,(struct sockaddr *) &serv_addr,sizeof(serv_addr)) < 0) error("ERROR connecting");
    while(1)
    {
       printf("Enter a command: ");
       bzero(sbuffer,sizeof(sbuffer));
       fgets(sbuffer,255,stdin);
       n = write(sockfd,sbuffer,5);
       if (n < 0) error("ERROR writing to socket");
       bzero(rbuffer,sizeof(rbuffer));
       n = read(sockfd,rbuffer,255);
       if (n < 0) error("ERROR reading from socket");
       printf("%sn",rbuffer);
       if (strcasecmp(sbuffer, "extn") == 0) break;
    }
    close(sockfd);
    return 0;
}

Answer 1

一个进程将在 ps 输出中显示为"失效"（有时称为僵尸进程），直到它的退出状态将被收集wait()或waitpid()。

有以下方法可以摆脱这些僵尸进程：

1. 在父进程中使用wait()或waitpid()等待子完成。显然，很难以这种方式在父级中做任何其他事情。
2. 生成子线程后立即创建一个单独的线程，并在此线程中waitpid。
3. 在您的父级中，安装 SIGCHLD 信号的处理程序，并在此处理程序中安装waitpid()。
4. 如果您的系统允许，请设置为忽略 SIGCHLD 信号。