Generating packets in C - c

Question

I am not receiving anything in buffer. Wherever I printf my buffer, it is always empty or shows garbage value. Can anyone help?
I defined header, packet and called them in my main, but buffer still shows garbage.
#include <stdint.h>
struct header {
uint16_t f1;
uint16_t f2;
uint32_t f3;
};
struct data {
uint16_t pf1;
uint64_t pf2;
};
#include <arpa/inet.h>
#include <string.h>
#include <stdint.h>
#include "packet.h"
void htonHeader(struct header h, char buffer[8]) {
uint16_t u16;
uint32_t u32;
u16 = htons(h.f1);
memcpy(buffer+0, &u16, 2);
printf("Value of buff is: %hu\n",buffer);
u16 = htons(h.f2);
memcpy(buffer+2, &u16, 2);
u32 = htonl(h.f3);
memcpy(buffer+4, &u32, 4);
}
void htonData(struct data d, char buffer[10]) {
uint16_t u16;
uint32_t u32;
u16 = htons(d.pf1);
memcpy(buffer+0, &u16, 2);
u32 = htonl(d.pf2>>32);
memcpy(buffer+2, &u32, 4);
u32 = htonl(d.pf2);
memcpy(buffer+6,&u32, 4);
}
void HeaderData(struct header h, struct data d, char buffer[18]) {
htonHeader(h, buffer+0);
htonData(d, buffer+8);
printf("buff is: %s\n",buffer);
}
#include <stdio.h>
#include "packet.c"
#include <string.h>
#include<stdlib.h>
int main(){
struct header h;
struct data d;
char buff[18];
//printf("Packet is: %s\n",buff);
printf("Generating Packets..... \n");
h.f1=1;
d.pf1=2;
h.f2=3;
d.pf2=4;
h.f3=5;
HeaderData(h,d,buff);
strcat(buff,buff+8);
printf("Packet is: %s\n",buff);
return 0;
}

Answer 1

The problem is that your printf()s are either syntactically wrong (printf( "%hu", ... ); expects an unsigned short as parameter, but you pass a pointer) or you try to print buff by using "%s" but the content is binary, not text. What you could do instead was doing some kind of hexdump, like:
int i;
for( i=0; i<sizeof( buff ); i++ ) {
printf( "%x ", buff[i] & 0xff );
}
puts( "" ); // terminate the line
Please note, that using sizeof works im main() only, in the other function you've got to determine the buffer size differently.
Besides: because of the binary content of buff, you can't use strcat(). Even if you have made sure that there is a '\0' behind the last value you have copied (I haven't checked if you have), depending on the integer values you copy, there may be another '\0' value before that one and strcat() would overwrite everything form that point on.