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。每次我关闭客户端或输入退出命令时，该过程似乎都无法关闭。选中ps aux| grep server时，会有一个解决过程。我怎样才能摆脱它们，在关闭分叉的时候我做错了什么。

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通过wait()或{{1}收集}。

有以下方法可以摆脱那些僵尸进程：

在父进程中使用waitpid()或wait()等待子级完成。显然，以这种方式在父母身上做其他事情很难。
在此线程中生成子项waitpid()后立即创建一个单独的线程。
在您的父级中，在此处理程序中安装SIGCHLD信号和waitpid的处理程序。
如果您的系统允许，请设置忽略SIGCHLD信号。

在套接字服务器中杀死分叉进程

1 个答案: