#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <signal.h>
#include <sys/wait.h>
#include <sys/socket.h>

#define BUF_SIZE 30
void error_handling(char *message);
void read_childproc(int sig);

int main(int argc, char *argv[]){
int serv_sock,clnt_sock;
pid_t pid;
struct sigaction act;
char buf[BUF_SIZE];
int str_len,state;
struct sockaddr_in serv_adr;
struct sockaddr_in clnt_adr;
socklen_t adr_sz;

if(argc != 2){
printf("Usage : %s <port>\n",argv[0]);
exit(1);
}

act.sa_handler = read_childproc;
sigemptyset(&act.sa_mask);
act.sa_flags = 0;
state = sigaction(SIGCHLD,&act,0);

serv_sock = socket(PF_INET,SOCK_STREAM,0);
if(serv_sock == -1){
error_handling("socket error");
}

memset(&serv_adr,0,sizeof(serv_adr));
serv_adr.sin_family=AF_INET;
serv_adr.sin_addr.s_addr=htonl(INADDR_ANY);
serv_adr.sin_port=htons(atoi(argv[1]));

if(bind(serv_sock,(struct sockaddr*)&serv_adr,sizeof(serv_adr)) == -1){
error_handling("bind() error");
}

if(listen(serv_sock,5) == -1){
error_handling("listen() error");
}

while(1){
adr_sz = sizeof(clnt_adr);
clnt_sock = accept(serv_sock,(struct sockaddr *)&clnt_adr,&adr_sz); //创建请求套接字
if(clnt_sock == -1){
continue;
}else{
printf("new client ...\n");
}

pid = fork();//创建子进程

if(pid == -1){
close(clnt_sock);//创建失败直接continue
continue;
}else if(pid == 0){
close(serv_sock);//若是子进程，就关闭服务器套接字，子进程
while((str_len = read(clnt_sock,buf,BUF_SIZE)) != 0){
write(clnt_sock,buf,str_len);
}

close(clnt_sock);
puts("client disconnected...");
return 0;
}else{
close(clnt_sock);
}
}
close(serv_sock);

return 0;
}

void error_handling(char *message){

fputs(message,stderr);
fputs("\n",stderr);
exit(1);
}

void read_childproc(int sig){
pid_t pid;
int status;
pid = waitpid(-1,&status, WNOHANG);
printf("removed proc id : %d \n",pid);
}