tftpclient.c

tftpclient.c

/* gcc -Wall -Wextra -ggdb -pedantic -o tftpclient tftpclient.c */ 
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <string.h>
#include <sys/types.h>
#include <fcntl.h>
#include <sys/stat.h>

#define MODE "netascii"
#define PORT 6969

int main(int c,char *v[])
{
char b[516];
int s,f,x;
unsigned int l;
struct sockaddr_in a,t;

if(c!=3)exit(1);

bzero(b,sizeof(b));
b[1]=1;
strcpy(b+2,v[2]);
strcpy(b+3+strlen(v[2]),MODE);

a.sin_family=AF_INET;
a.sin_port=htons(PORT);
a.sin_addr.s_addr=inet_addr(v[1]);

s=socket(PF_INET,SOCK_DGRAM,0);
sendto(s,b,4+strlen(MODE)+strlen(v[2]),0,(struct sockaddr*)&a,sizeof(struct sockaddr));
f=open(v[2],O_WRONLY|O_CREAT,S_IRUSR|S_IWUSR);

l=sizeof(struct sockaddr);

while((x=recvfrom(s,b,sizeof(b),0,(struct sockaddr*)&t,&l))==516)

{

if(b[1]!=3)exit(1); 
if(b[3]==1){
close(s);

a.sin_port=t.sin_port;
s=socket(PF_INET,SOCK_DGRAM,0);

}

write(f,b+4,512);
b[1]=4;

sendto(s,b,4,0,(struct sockaddr*)&a,sizeof(struct sockaddr));

}

if(x>=4){

write(f,b+4,x-4);
b[1]=4;

sendto(s,b,4,0,(struct sockaddr*)&a,sizeof(struct sockaddr));

}

close(f);
return 0;

}