//pragma pack(4)

//#define WIN32_LEAN_AND_MEAN

#include <winsock2.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#pragma comment(lib,"ws2_32")

#define BUFSIZE			8192
#define DEFAULT_PORT	5320
enum {CMD_NAME,DST_PORT};

void InitWinSocket();
void ParseCmdLine(int* port,int argc,char*strPort);
void CreateUdpSocket(SOCKET* listen_sock);
void BindToIPAndPort(SOCKET listen_sock,int port,unsigned long IP);
void ServeForClients(SOCKET listen_sock); 
int  ParseClientCmdAndExecute(int cn,char*cmd1,char*cmd2,
							  char*send_buf,int bufsize);
int  execute(char* command,char*buf,int bufmax);
int ExecuteCmd(char*cmd,char*send_buf,int bufsize);

int main(int argc, char *argv[]){ 
	int port;
	SOCKET listen_sock;

	InitWinSocket();
	ParseCmdLine(&port,argc,argv[DST_PORT]);
	CreateUdpSocket(&listen_sock);
	BindToIPAndPort(listen_sock,port,INADDR_ANY);
	ServeForClients(listen_sock); 
	closesocket(listen_sock);
	WSACleanup(); 
	getchar();
	return 0;
}

void InitWinSocket(){
	WSADATA wsaData;
	if (WSAStartup(MAKEWORD(2,1),&wsaData) != 0){
	fprintf(stderr,"WSAStartup failed: %d\n",GetLastError());
	exit(EXIT_FAILURE);
  }
}

void ParseCmdLine(int* port,int argc,char*strPort){
	if(argc == 2){
		if((*port=atoi(strPort))==0){
			struct servent*se;
			if((se=getservbyname(strPort,"UDP"))!=NULL)
				*port=(int)ntohs((u_short )se->s_port);
			else{
				fprintf(stderr,"Getservbyname error");
				exit(EXIT_FAILURE);
			}
		}
	}else	*port=DEFAULT_PORT;
}

void CreateUdpSocket(SOCKET* listen_sock){
	if((*listen_sock=socket(AF_INET,SOCK_DGRAM,0))<0){
		perror("socket");
		exit(EXIT_FAILURE);
	}
}

void BindToIPAndPort(SOCKET listen_sock,int port,unsigned long IP){
	struct sockaddr_in server;
	memset((char*)&server,0,sizeof(server));
	server.sin_family=AF_INET;
	server.sin_addr.s_addr=htonl(IP);
	server.sin_port=htons(port);
	
	if(bind(listen_sock,
		(struct sockaddr*)&server,
		sizeof(server))<0){

		perror("bind");
		exit(EXIT_FAILURE);
	}
}

void ServeForClients(SOCKET sock){ 
	struct sockaddr_in client;
	int cn,sn,rn,len;
	
	char cmd1[BUFSIZE];
	char cmd2[BUFSIZE];
	char recv_buf[BUFSIZE];
	char send_buf[BUFSIZE];
	len=sizeof(client);

	while((rn=recvfrom(sock,recv_buf,BUFSIZE-1,0,
						(struct sockaddr*)&client,&len))>=0){
		recv_buf[rn]='\0';
		printf("receive %s from %s\n",recv_buf,inet_ntoa(client.sin_addr));
		cn=sscanf(recv_buf,"%s %s",cmd1,cmd2);
		sn=ParseClientCmdAndExecute(cn,cmd1,cmd2,send_buf,BUFSIZE);
		if(sn==0){
			sn=sprintf(send_buf,"Command error %s \n",cmd1);
			printf("%d",sn);
		}
		if(sendto(sock,send_buf,sn,0,(struct sockaddr*)&client,len)<0){
			printf("sendto error!");
			break;
		}
		printf("%s",send_buf);

	}

}
int ParseClientCmdAndExecute(int cn,char*cmd1,char*cmd2,
			char*send_buf,int bufsize){
	int sn;
	switch(cn){
		case 2:
			if(strcmp(cmd1,"show")==0)
				sn=ExecuteCmd(cmd2,send_buf,bufsize);
			else sn=0;
			break;
		case 1:
			if(strcmp(cmd1,"quit")==0)	sn=0;
			else{
				send_buf[0]='\0';
				if(strcmp(cmd1,"help")!=0)
					sprintf(send_buf,"command error %s\n",cmd1);
				strcat(send_buf,"Command: \n"
									"show route \n"
									"show arp \n"
									"show nic \n"
									"quit \n"
									"help \n");
				sn=strlen(send_buf);
			}
			break;
		default:
				sn=0;
				break;
		}
	return sn;
}


int ExecuteCmd(char*cmd,char*send_buf,int bufsize){
	int sn;
	if(strcmp(cmd,"route")==0)
		sn=execute("netstat -rn",send_buf,bufsize);
	else if(strcmp(cmd,"arp")==0)
		sn=execute("arp -a",send_buf,bufsize);
	else if(strcmp(cmd,"tcp")==0)
		sn=execute("netstat -a",send_buf,bufsize);
	else if(strcmp(cmd,"nic")==0)
		sn=execute("ipconfig /all",send_buf,bufsize);
	else{
		sn=sprintf(send_buf,"Parameter error %s \n"
					"show[route |arp|tcp|nic\n",cmd);
		printf("%s",send_buf);
		}
	return sn;
}

int execute(char*command,char*buf,int bufmax){
	FILE *fp;
	int i;
	if((fp=_popen(command,"r"))==NULL){
		perror(command);
		exit(EXIT_FAILURE);
	}
	i=0;
	while((buf[i]=fgetc(fp))!=EOF && i<bufmax)i++;
	buf[i]=0;
	_pclose(fp);
	return i;
}