#include<stdio.h>
#include<stdlib.h>
#include<sys/types.h>
#include<signal.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<arpa/inet.h>
#define MAXLINE 1024

int readline(int,char *,int);
char *escapechar = "exit\n";

int main(int argc,char *argv[]){
	int i,ch;
	int server_fd,client_fd;
	int clilen,num;
	char sendline[MAXLINE],rbuf[MAXLINE],buff[MAXLINE];
	int size,size2;
	pid_t pid;
	struct sockaddr_in client_addr,server_addr;
	FILE *send;
	
	if(argc<2){
		perror("Usage: talk_server 3000");
		exit(1);
	}
	if((server_fd=socket(PF_INET,SOCK_STREAM,0))<0){
		printf("Server : Can't open stream socket\n");
		exit(1);
	}

	bzero((char *) &server_addr,sizeof(server_addr));
	server_addr.sin_family = AF_INET;
	server_addr.sin_addr.s_addr = htonl(INADDR_ANY);
	server_addr.sin_port = htons(atoi(argv[1]));		// ÀԷ¹ÞÀº ÆĶó¹ÌÅÍ º¯¼ö¸¦ ÀÌ¿ëÇÏ¿© Æ÷Æ® ¹øÈ£ ÁöÁ¤
	if(bind(server_fd,(struct sockaddr*)&server_addr,sizeof(server_addr))<0){
		printf("Server: Can't bind local address\n");
		exit(1);
	}
	printf("Server started.\nWaiting for client..");
	if(listen(server_fd,1)<0){
		perror("Listen error : ");
		exit(1);
	}
	clilen = sizeof(client_addr);
	
	if((client_fd = accept(server_fd,(struct sockaddr*)&client_addr,&clilen)) != -1){
		printf("\n\n========== Server : »ç¿ëÀÚ°¡ Á¢¼ÓÇÏ¿´½À´Ï´Ù. ==========\n\n");
	}
	else{
		printf("\n\n========== Server : Á¢¼Ó¿¡ ½ÇÆÐÇÏ¿´½À´Ï´Ù. ===========\n\n");
		exit(1);
	}

	if((pid=fork())>0){
		while(readline(0,sendline,MAXLINE)!=0){
			size=strlen(sendline);
			if(write(client_fd,sendline,size)!=size){
				printf("Server:fail in writing\n");
			}
			if(strncmp(sendline,escapechar,4)==0){
				printf("Client disconnected\n");
				kill(pid,SIGQUIT);
				break;
			}
		}
	}
	else if(pid==0){
		while(1){
			if((size=read(client_fd,rbuf,MAXLINE))>0){
				rbuf[size] = '\0';
				if(strncmp(rbuf,escapechar,4)==0){
					kill(getppid(),SIGQUIT);
					break;
				}

				if(strncmp(rbuf,"**",2)==0){
					send=popen(rbuf+2,"r");
					if(send==NULL){
						perror("Error : ");
						exit(1);
					}
					while(fgets(buff,MAXLINE,send) !=NULL){
						printf("%s",buff);
						size2=strlen(buff);
						if(write(client_fd,buff,size2)!=size2){
							printf("Server:fail in writing\n");
						}
					}
					pclose(send);
				}
				printf("Client : %s",rbuf);
			}
		}
	}

	printf("========== Á¢¼ÓÀ» ²÷½À´Ï´Ù. ==========\n\n");
	close(server_fd);
	close(client_fd);
	return 0;
}

int readline(int fd,char *ptr,int maxlen){
	int n,rc;
	char c;
	for(n=1;n<maxlen;n++){
		if((rc=read(fd,&c,1))==1){
			*ptr++ = c;
			if( c=='\n') break;
		}
		else if(rc==0){
			if(n==1) return 0;
			else break;
		}
	}
	*ptr=0;
	return n;
}