之前我们已经编写了一个http://www.2cto.com/kf/201201/116006.html，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 /* 提供类型pid_t的定义 */
#include
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
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
#include
#include
#include
#include
#include
#include
#include
#include /* exit declare */
#include /* 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 sock