#include <sys/types.h>#include <sys/socket.h>#include <stdio.h>#include <netinet/in.h>#include <signal.h>#include <unistd.h>#include "err_exit.h"#include "socketfun.h"void doit(int client_sockfd);int main(int argc,char ** argv){	int server_sockfd,client_sockfd;	int server_len,client_len;	struct sockaddr_in client_address;	server_sockfd=make_socket(PARALLELPORT);		/* 創建連接隊列，忽略子進程終止信號 */	listen(server_sockfd,LISTENQ);	signal(SIGCHLD,SIG_IGN);	while(1){		printf("server waiting\n");		/* 接收連接 */		client_len=sizeof(client_address);		client_sockfd=accept(server_sockfd,(struct sockaddr *)&client_address,&client_len);				/* 為這個客戶創建一個子進程 */		if(fork()==0){						/* 若為子進程，接收并回答客戶的消息 */			close(server_sockfd);			/* 子進程關閉偵聽套接字 */			doit(client_sockfd);			/* 處理客戶的請求 */			close(client_sockfd);			/* 已處理完該客戶的請求 */			exit(0);						/* 子進程終止 */		}else{			close(client_sockfd);			/* 父進程關閉被連接的套接字 */			}	}}void doit(int client_sockfd){	char buf[MAXBUFFSIZE];	int n;		/* 接收并回應客戶的消息 */	n=read(client_sockfd,buf,sizeof(buf));	buf[n]=0;	printf("string from cliet=%s\n",buf);	sleep(5);		write(client_sockfd,buf,n);	}