基于UDP的TFTP客户端

 

#include<stdio.h>
#include<sys/socket.h>
#include<sys/types.h>
#include<sys/stat.h>
#include<arpa/inet.h>
#include<netinet/in.h>
#include<unistd.h>
#include<stdlib.h>
#include<string.h>
#include<fcntl.h>
#define PACKLEN 516
#define ACKLEN 4
int main(int argc,char *argv[])
{
 int sock_fd,fd;
 int recv=0;
 char buf[1024]="",ack_packet[ACKLEN]="",req_packet[PACKLEN]="";
 unsigned short port = 69;
 struct sockaddr_in srv_addr,srv_addr2;
 size_t ip_len = sizeof(srv_addr2);

 bzero(&srv_addr,sizeof(srv_addr));

 srv_addr.sin_family = AF_INET;
 srv_addr.sin_port = htons(port);
 inet_pton(AF_INET,argv[1],&srv_addr.sin_addr);

 sock_fd = socket(AF_INET,SOCK_DGRAM,0);

 sprintf(req_packet,"%c%c%s%c%s%c",0,1,argv[2],0,"octet",0);

 recv = sendto(sock_fd,req_packet,sizeof(req_packet),0,(struct sockaddr*)&srv_addr,sizeof(srv_addr));

 if(recv == -1)
 {
  perror("sendto");
  exit(-1);
 }

 fd=open(argv[2],O_RDWR|O_CREAT,0666);

 if(fd < 0)
 {
  perror("open");
  exit(0);
 }

 while(1)
 {
  recv=recvfrom(sock_fd,buf,PACKLEN,0,(struct sockaddr*)&srv_addr2,&ip_len);
  if( 3 == (char)buf[1])
  {
   //if( num == (short)(buf+2))
   //write(fd,buf+4,strlen(buf+4));
    //else
   //{
   // printf("recv wrong packets\n");
   // break;
   //}
   if( recv < 516 )
   {
    write(fd,buf+4,recv-4);
    break;
   }
   else
    write(fd,buf+4,recv-4);
  }

  if( 4 == (char)buf[1])
  {
   printf("%s\n",buf+4);
   break;
  }
  sprintf(ack_packet,"%c%c%c%c",0,4,0,0);
  memcpy(ack_packet+2,buf+2,2);
  sendto(sock_fd,ack_packet,ACKLEN,0,(struct sockaddr*)&srv_addr2,sizeof(srv_addr2));
 }
 close(fd);
 close(sock_fd);
 return 0;
}