网络编程Server端 --- Linux版

       之前我们已经编写了一个通用的Socket服务器端程序，我们现在增加对此类操作系统特性的一些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;}

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