杀死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分配，但我似乎无法摆脱分叉进程。每次关闭客户端，或者输入exiting命令，进程好像都没有关闭。选中 ps aux| grep server 时，有一个失败的进程。我怎样才能摆脱它们，关闭分叉过程时我做错了什么。

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, "tim\n") == 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, "dat\n") == 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, "day\n") == 0)
     {
        rawtime = time(NULL);
        strncpy(day, "Current day: ", 13);
        strncpy(day+13, (ctime(&rawtime)), 3);
        n = write(sock, day, 16);
     }
     else if (strcasecmp(buffer, "yer\n") == 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, "com\n") == 0)
     {
        n = write(sock, "TIM - current time\nDAT - Month and day\nDAY - current weekday\nYER - Year\nEXT - exit", 82);
     }
     else if (strcasecmp(buffer, "ext\n") == 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 port\n", 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 host\n");
        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("%s\n",rbuffer);

       if (strcasecmp(sbuffer, "ext\n") == 0) break;
    }
    close(sockfd);
    return 0;
}

Answer 1

一个进程将在 ps 输出中显示为 'defunct'（有时称为 zombie 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那些僵尸进程：

在父进程中使用 wait() 或 waitpid() 等待子进程完成。显然，这种方式很难在父级中做任何其他事情。
在生成子项后立即创建一个单独的线程并waitpid在此线程内。
在您的父级中，为 SIGCHLD 信号安装一个处理程序，并在该处理程序中安装 waitpid()。
如果您的系统允许，请设置为忽略 SIGCHLD 信号。

杀死套接字服务器中的分叉进程

Killing forked process in a socket server

c

sockets

fork

defunct