/* ==========================================================

download.c   

*==========================================================*/

/*

 * run a daemon to accept download request from client 

 */

#include <stdio.h>

#include <stdlib.h>



#include <sys/types.h>    //socket ,bind , listen ,accept 

#include <sys/socket.h>

#include <netinet/in.h>   //inet_addr(char *p)

#include <arpa/inet.h>   



#include <netdb.h>    

#include <string.h>



#include <unistd.h>

#include <sys/stat.h>



#include <sys/wait.h>  //waitpid function



#include <errno.h>	//errno



#include "download.h"



#define PORT 9000		//port of Download Server

#define MAX_SUPPORT_CLIENT	100



#define BIND_FAILURE  		-1 

#define SOCKET_FAILURE 		-2 

#define ACCEPT_FAILURE 		-3 

#define RECIEVE_FAILURE 	-4

#define SEND_FAILURE		-5



/* 

 * Generate a child process

 */

void init_child(void) {

	pid_t pid = 0;

	pid = fork();

	if (pid < 0) {

		printf("Program fork fail
");

		exit(-1);

	} else if (pid != 0) {

		exit(0);	/* parent goes bye-bye */

	}

				/* child continues */

	setsid();		/* standard daemon procedure */

	//for(i=0;i<64;i++)

	//	close(i);

	close(0);

	close(1);

	close(2);

	chdir("/");

	umask(0);

}



void sigChildHandler(int signo)

{

	int status; 

	wait(&status);

	while(status > 0 || (status < 0 && errno==EINTR)) {

		wait(&status);

	}

}



int main(void)

{

	struct sockaddr_in local_addr_in ;

	struct sockaddr_in client_addr_in;

		

	int sock_fd = 0;

	int source_client_fd = 0;



	int on = 1;



	int address_size = 0;

	int rc = 0;	//the return value of all socket operation

	

	struct sigaction sig_act;  //you must define a sigaction that will be associated with

a SIGCHLD

	



	init_child();	//the main process will become a daemon 

	

	sock_fd = socket(AF_INET, SOCK_STREAM, 0); 	/* create a socket */

	/* the sock_fd is blocked ,you can set it non-block ,

	 * with fuction fcntl,fcntl(sock_fd,F_SETFL,O_NONBLOCK);  

	 */

	if(sock_fd < 0)

	{

		perror("Creating Socket Error!
");

		exit(SOCKET_FAILURE);

	}



	//add setsockopt , you can lose the messages "address already used"

	if( setsockopt(sock_fd,SOL_SOCKET,SO_REUSEADDR,&on, sizeof(int)) < 0)

	{

		perror("setsockopt error
");

		exit(-1);

	}

	

	memset(&local_addr_in,'',sizeof(local_addr_in));

	local_addr_in.sin_family 		= AF_INET;

	local_addr_in.sin_addr.s_addr 	= htonl(INADDR_ANY);	//automatically fill with my IP

Address  

	local_addr_in.sin_port  		= htons(PORT);

	//maybe , you should empty local_addr_in.sin_zero 

	memset((char *)&(local_addr_in.sin_zero),'',8);



	rc = bind(sock_fd,(struct sockaddr *)&local_addr_in,sizeof(struct sockaddr)); 

	if(rc < 0) {

		perror("bind failure
");

		exit(BIND_FAILURE);

	}

	

	sig_act.sa_handler = sigChildHandler ; 

	sigemptyset(&sig_act.sa_mask);

	sig_act.sa_flags = SA_RESTART;



	/* -------------register signal handler ---------*/

	if( sigaction(SIGCHLD,&sig_act,NULL) < 0) {

		perror("Register signal Handler Failure
");

		exit(-1);

	}

	//begin to listen the requests from any client 

	listen(sock_fd,MAX_SUPPORT_CLIENT);		//accept 20 connection 

	printf("Begin to be accepting downloading request ...................
");

	

	

	

	//----------Begin to deal with request from Client ----------

	while(1)   //it will looply deal the client's connection continously 

	{

		pid_t child_pid = 0;

		

		source_client_fd = accept(sock_fd,(struct sockaddr

*)&client_addr_in,&address_size);//address_size is no usefull 

		if(source_client_fd < 0) {

			perror("Accept from clients failure !
");

			exit(ACCEPT_FAILURE);

		}

		

		//into child process 

		child_pid = fork();

		if(child_pid < 0) { //fork failure 

			perror("fork() failure ");

			exit(-1);

		}

		else if(child_pid == 0) {		//into child process

			unsigned char buffer[255];	//this buffer will contain the cmd content ,so it must

unique ,when want to send , rewrite the buffer 

			struct DownloadPacket * Packet = NULL;



			memset(buffer,'',sizeof(buffer));

						

			close(sock_fd);	//child process doesn't need socket FD

			

			//begin to recieve data from the temp socket descriptor 

			rc = recv(source_client_fd,buffer,sizeof(buffer)-1,0);

			printf("recieve length is %i
",rc);



			if(rc < 0) {

				perror("recieve data from client ,failure !
");

				exit(RECIEVE_FAILURE);	

			}

			printf("Server has recieved data from %s , contents is %s
", 

				inet_ntoa(client_addr_in.sin_addr), buffer);

		

			//-----------judge the CMD type  ---------

			Packet = (struct DownloadPacket *)buffer;

			switch (Packet->cmd_type)

			{

				case SEARCH_DLSERVER_CMD :	//client request NAS Download Server

					;

					break;

				case DLREQUEST_CMD :

					;

					break;

				case DLSTATUS_QUERY_CMD :

					;

					break;

				default:

					printf("this packet is a invalid packet 
");

			}

			exit(0);	//once the child process exited ,it will trigger SIGCHILD signal ,

				//the kernel will call sigChildHandler function to reclaim the child process 

		} //end of else if

		else { 

			close(source_client_fd);	//parent doesn't need this socket fd ,which has been used

by child process 

		}	

	} //end of while(1)

	return 0;

}







download.h  为：

/*

 * Download Program , Author by bob_zhang  

 * Function : it is a server that can accept some download request from client

(typically in Windows) ,it really acts the download function

 * and store them into \NAS_BIOSNAMEdiskdownloads directory

 *

 *download.h 

 */

 

 

#define IP_MAX_LENGTH 16

#define URL_MAX_LENGTH 255

#define FILENAME_MAX_LENGTH	255

#define NETBIOSNAME_MAX_LENGTH	255



//error NO   



#define DLOADING_OK 	0

#define DLOADING_ERR	-1

#define DLOADED_OK	0





enum cmd_type {

	SEARCH_DLSERVER_CMD=0x01,//Windows client will search a NAS download Server 

	DLSERVER_ACK_CMD,     	//0x02, Download server give a ACK to client ,to represent its

status including NetBIOS name and IP

	

	DLREQUEST_CMD,		//0x03, Windows client will send a download request to NAS download

Server

	DLACK_CMD,		//0x04,NAS download server give a ACK to client 's downloading request 

	

	DLSTATUS_QUERY_CMD,	//0x05,windows client will query NAS download server's status

,which file downloading status 

	DLSTATUS_ACK_CMD	//0x06,NAS download server will represents its own status 

}





struct SearchDownloadServerRequest {

	char ClientIP[IP_MAX_LENGTH];	//only tell Server its own IP address	

}



struct DownloadServerAck {

	char NetBIOSName[NETBIOSNAME_MAX_LENGTH];

	char DlServerIP[IP_MAX_LENGTH];

	int   RetValue;			

}



struct DownloadRequest {

	char ClientIP[IP_MAX_LENGTH];

	char URLString[URL_MAX_LENGTH];

}



struct DownloadAck {

	int RetValue ;	//return value of excuting the downloading tool  ,OK or fail 

}



struct DownloadStatusQueryRequest {

	char ClientIP[IP_MAX_LENGTH];

	char URLString[URL_MAX_LENGTH];

}



struct DownloadStatusQueryAck {

	char 		URLString[URL_MAX_LENGTH];	//for example, href=http://www.kernel.org/2.4.19.tar.gz>http://www.kernel.org/2.4.19.tar.gz

	char 		FileName[FILENAME_MAX_LENGTH];	//for example , 2.4.19.tar.gz

	char 		SavePath[255];			// \SCFD529Bdiskdownloads2.4.19.tar.gz

	unsigned int	FileSize ;				//byte	

	unsigned int 	RecvByte;			//byte

	unsigned int 	RecvRate;  			//%	

	char 		ElapseTime[9];			//for example: 00:01:10  ,elapse 1minutes 10seconds 

	char		LeftTime[9];			//for example: 01:09:07 , left time :1hour ,9 minutes ,7seconds



	unsigned int 	AverageSpeed;			//KB/s

	int 		isFinished;			//1: finished ,non-1:downloading 

}  



struct DownloadPacket {

	unsigned int cmd_type ; 

	union {

		struct SearchDownloadServerRequest 	SearchDownloadServerRequestPack ;

		struct DownloadServerAck 		DownloadServerAckPack;

		

		struct DownloadRequest 			DownloadRequestPack;

		struct DownloadAck 			DownloadAckPack;

		

		struct DownloadStatusQueryRequest 	DownloadStatusQueryRequestPack ; 

		struct DownloadStatusQueryAck 		DownloadStatusQueryAckPack;

	}data;

}