TFTP Server Is Not Sending DATA packets - c

Question

I wrote a simple tftp server that only handles read requests (RRQ) from clients. The problem is that the server seems not to be sending DATA packets to the client. I made sure that the server is not sending the DATA packet through checking the length of the sent bytes against the data packet size.
Note: I use the standard tftp client that comes with linux.
Here's the code I've written so far...
#include <stdio.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
void sendFile (char *Filename, char *mode, struct sockaddr_in client)
{
char path[70] = "tmp/";
char filebuf [1024];
int acked = 0; // Number of acked data portions
int count = 0; // Number of data portions we sent
unsigned char packetbuf[1024];
char recvbuf[1024];
socklen_t recv_size;
int sock = socket(PF_INET, SOCK_DGRAM, 0);
FILE *fp;
char fullpath[200];
strcpy(fullpath, path);
strncat(fullpath, Filename, sizeof(fullpath) -1);
fp = fopen(fullpath, "r");
if (fp == NULL)
perror("");
memset(filebuf, 0, sizeof(filebuf));
while (1)
{
int ssize = fread(filebuf, 1 , 512, fp);
count++;
sprintf((char *) packetbuf, "%c%c%c%c", 0x00, 0x03, 0x00, 0x00);
memcpy((char *) packetbuf + 4, filebuf, ssize);
packetbuf[2] = (count & 0xFF00) >> 8;
packetbuf[3] = (count & 0x00FF);
int len = 4 + ssize;
if (sendto(sock, packetbuf, len, 0, (struct sockaddr *) &client, sizeof(client)) != len)
puts("SENDING FAILED!");
memset(recvbuf, 0, 1024);
recvfrom(sock, recvbuf, 1024, 0, (struct sockaddr *) &client, &recv_size);
if (recvbuf[1] == 4)
puts("Acked");
if (ssize != 512)
break;
}
}
int main()
{
int udpSocket, nBytes;
char buffer[1024], filename[200], mode[20], *bufindex, opcode;
struct sockaddr_in serverAddr, client;
struct sockaddr_storage serverStorage;
socklen_t addr_size;
udpSocket = socket(AF_INET, SOCK_DGRAM, 0);
serverAddr.sin_family = AF_INET;
serverAddr.sin_port = htons(69);
serverAddr.sin_addr.s_addr = inet_addr("127.0.0.1");
memset(serverAddr.sin_zero, '\0', sizeof serverAddr.sin_zero);
bind(udpSocket, (struct sockaddr *) &serverAddr, sizeof(serverAddr));
memset(buffer,0,1024);
while(1)
{
nBytes = recvfrom(udpSocket,buffer,1024,0,(struct sockaddr *)&client, &addr_size);
bufindex = buffer;
bufindex++;
// Extracting the opcode from the packet...
opcode = *bufindex++;
// Extracting the filename from the packet...
strncpy(filename, bufindex, sizeof(filename)-1);
bufindex += strlen(filename) + 1;
// Extracting the mode from the packet...
strncpy(mode, bufindex, sizeof(mode)-1);
// If we received an RRQ...
if (opcode == 1)
sendFile(filename, mode, client);
}
return 0;
}
Thanks in advance :)

Answer 1

Your opcode check appears to be incorrect.
Try:
bufindex++;
opcode = *bufindex++;
Also, why 1024 bytes in sendto. Shouldn't it be size of file? You are just passing on the size of the packetbuf instead of actual size of file.
Change to :
sendto((sock, packetbuf, len, 0, (struct sockaddr *) &client, sizeof (client)) );