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; }

End.