网络编程Server端 --- Linux版

之前我们已经编写了一个，我们现在增加对此类操作特性的一些code！

       大家都知道fork() 只有在unix/linux类操作系统才有！因为他们没有线程这一说。他们只有子进程。

       要用到fork那么就必须用到 waitpid() ！

       waitpid函数原型：

 

       #include<sys/types.h>   /* 提供类型pid_t的定义 */

       #include<sys/wait.h>

 

       pid_twaitpid(pid_tpid, int *status, int options);

 

       参数pid=-1时，等待任何一个子进程退出，没有任何限制，此时waitpid和wait的作用一模一样。

       参数 status我们设置为null。

       参数options提供了一些额外的选项来控制waitpid，wnohang常量表示，即使没有子进程退出，它也会立即返回，不会像wait那样永远等下去。

       我们希望只有给waitpid()信号时，才使用它！

       这时，我们需要另外一个函数sigaction()。

       sigaction函数原型：

       #include<signal.h>

 

   int sigaction(int signum, const struct sigaction *act, struct sigaction *oldact);

 

       参数 signum=sigchld时，只有子进程停止或者退出才进行调用。

       参数 act是一个指向sigaction结构的指针。

       参数 oldact一般废止不用。

 

       我们主要设置结构sigaction的sa_handler、sa_mask和sa_flags三个成员变量即可！

      

       下面是示例：

 /**
 * version: 0.2
 *
 * description: add signal
 *
 */ 
 
#include <stdio.h>  
#include <string.h>  
#include <sys/types.h>  
#include <sys/socket.h>  
#include <netdb.h>  
#include <arpa/inet.h>  
#include <signal.h>  
#include <sys/wait.h>  
#include <stdlib.h>       /* exit declare */  
#include <unistd.h>       /* fork declare */  
 
#define servport "2349"  
 
void sigchild_handler() 
{ 
    while (waitpid(-1, null, wnohang) > 0);   
} 
 
int main(int argc, char *argv[]) 
{ 
    struct addrinfo hints, *res; 
    int status; 
    int sockfd; 
     
    int connfd; 
    /* struct sockaddr_in cliaddr;  only ipv4  */ 
    struct sockaddr_storage clientaddr; /* both ipv4 and ipv6 */ 
     
    struct sigaction sa; 
     
    int sendsta; 
    char *msg; 
     
    if (argc != 2) { 
        fprintf(stderr, "usage: not found read file"); 
        return 1; 
    } 
     
    memset(&hints, 0, sizeof(hints)); 
    hints.ai_family = af_unspec; 
    hints.ai_socktype = sock_stream; 
    hints.ai_flags = ai_passive; 
     
    status = getaddrinfo(null, servport, &hints, &res); 
     
    if (status != 0) { 
        fprintf(stderr, "getaddrinfo, fail!"); 
        return 2; 
    } 
     
    sockfd = socket(res->ai_family, res->ai_socktype, res->ai_protocol); 
     
    bind(sockfd, res->ai_addr, res->ai_addrlen); 
     
    listen(sockfd, 5); 
     
    printf("======== please wait client =========\n"); 
     
    /* struct sigaction notes from posix:
     *
     *  (1) routines stored in sa_handler should take a single int as
     *      their argument although the posix standard does not require this.
     *  (2) the fields sa_handler and sa_sigaction may overlap, and a conforming
     *      application should not use both simultaneously.
     */ 
    sa.sa_handler = sigchild_handler;    
    sigemptyset(&sa.sa_mask);   /* additional set of signals to be blocked */ 
                                /* during execution of signal-catching function. */ 
    sa.sa_flags = sa_restart;   /* special flags to affect behavior of signal */ 
                                /* sa_restart 0x10000000    // restart syscall on signal return */ 
                                 
    if (sigaction(sigchld, &sa, null) == -1) {  /* sigchld 20   // to parent on child stop or exit */ 
        fprintf(stderr, "sigaction fail!"); 
        exit(3);     
    } 
     
    while(1) { // loop forever!  
        char ipstr[inet_addrstrlen]; 
        void *addr; 
         
        int len = sizeof(clientaddr); 
        connfd = accept(sockfd, (struct sockaddr *)&clientaddr, &len); 
         
        /* view client ip */ 
        struct sockaddr_in *ipv4 = (struct sockaddr_in *)&clientaddr; 
        addr = &(ipv4->sin_addr); 
     
        inet_ntop(af_inet, addr, ipstr, sizeof(ipstr)); 
        printf("client: %s\n", ipstr); 
         
        if (!fork()) { 
            close(sockfd);  /* child doesn't need the listener */ 
            /* copy data */ 
            msg = "the server simply displays a message!"; 
            sendsta = send(connfd, msg, strlen(msg), 0); 
            if (sendsta == -1) 
                fprintf(stderr, "send fail!"); 
            close(connfd); 
            exit(0); 
        } 
         
        close(connfd); 
    } 
     
    close(sockfd); 
    return 0; 
} 
/**
 * version: 0.2
 *
 * description: add signal
 *
 */

#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <signal.h>
#include <sys/wait.h>
#include <stdlib.h>  /* exit declare */
#include <unistd.h>  /* fork declare */

#define servport "2349"

void sigchild_handler()
{
 while (waitpid(-1, null, wnohang) > 0); 
}

int main(int argc, char *argv[])
{
 struct addrinfo hints, *res;
 int status;
 int sockfd;
 
 int connfd;
 /* struct sockaddr_in cliaddr;  only ipv4  */
 struct sockaddr_storage clientaddr; /* both ipv4 and ipv6 */
 
 struct sigaction sa;
 
 int sendsta;
 char *msg;
 
 if (argc != 2) {
  fprintf(stderr, "usage: not found read file");
  return 1;
 }
 
 memset(&hints, 0, sizeof(hints));
 hints.ai_family = af_unspec;
 hints.ai_socktype = sock_stream;
 hints.ai_flags = ai_passive;
 
 status = getaddrinfo(null, servport, &hints, &res);
 
 if (status != 0) {
  fprintf(stderr, "getaddrinfo, fail!");
  return 2;
 }
 
 sockfd = socket(res->ai_family, res->ai_socktype, res->ai_protocol);
 
 bind(sockfd, res->ai_addr, res->ai_addrlen);
 
 listen(sockfd, 5);
 
 printf("======== please wait client =========\n");
 
 /* struct sigaction notes from posix:
   *
   *  (1) routines stored in sa_handler should take a single int as
   *      their argument although the posix standard does not require this.
   *  (2) the fields sa_handler and sa_sigaction may overlap, and a conforming
   *      application should not use both simultaneously.
   */
 sa.sa_handler = sigchild_handler; 
 sigemptyset(&sa.sa_mask); /* additional set of signals to be blocked */
                               /* during execution of signal-catching function. */
 sa.sa_flags = sa_restart; /* special flags to affect behavior of signal */
        /* sa_restart 0x10000000  // restart syscall on signal return */
        
 if (sigaction(sigchld, &sa, null) == -1) { /* sigchld 20 // to parent on child stop or exit */
  fprintf(stderr, "sigaction fail!");
  exit(3); 
 }
 
 while(1) { // loop forever!
  char ipstr[inet_addrstrlen];
  void *addr;
  
  int len = sizeof(clientaddr);
  connfd = accept(sockfd, (struct sockaddr *)&clientaddr, &len);
  
  /* view client ip */
  struct sockaddr_in *ipv4 = (struct sockaddr_in *)&clientaddr;
  addr = &(ipv4->sin_addr);
 
  inet_ntop(af_inet, addr, ipstr, sizeof(ipstr));
  printf("client: %s\n", ipstr);
  
  if (!fork()) {
   close(sockfd); /* child doesn't need the listener */
   /* copy data */
   msg = "the server simply displays a message!";
   sendsta = send(connfd, msg, strlen(msg), 0);
   if (sendsta == -1)
    fprintf(stderr, "send fail!");
   close(connfd);
   exit(0);
  }
  
  close(connfd);
 }
 
 close(sockfd);
 return 0;
}

 

end.

 摘自 xiaobin_hlj80的专栏