Programming :: TCP / UDP File Transfer In C Or C++

I need to create a program that has both a server and a client and can transmit PDF and text files between the two using UDP as the underlying carrier while behaving as if it is TCP. We have successfully created a UDP program that can simply transmit strings, but we are not really sure on how to transform this code to do files. We know that we need to use a buffer of some sort to transmit the file in pieces.

Code:
//dg_cli.c
#include "unp.h"
#include "sys/socket.h"
#include "string.h"
#include "stdio.h"
#include "stdlib.h"
#include "arpa/inet.h"
#include "netdb.h"
#include "sys/file.h"
#include "sys/types.h"

void dg_cli(FILE *fp, int sockfd, const SA *pservaddr, so
{ int n;
char sendline[MAXLINE], recvline[MAXLINE + 1];
while (fgets(sendline, MAXLINE, fp) != NULL) {
sendto(sockfd, sendline, strlen(sendline), 0, pse
n = recvfrom(sockfd, recvline, MAXLINE, 0, NULL,
recvline[n] = 0; /* null terminate */
fputs(recvline, stdout); } }

Code:
//dg_echo.c
#include "unp.h"
#include "sys/socket.h"
#include "string.h"
#include "stdio.h"
#include "stdlib.h"
#include "arpa/inet.h"
#include "netdb.h"
#include "sys/file.h"

void dg_echo(int sockfd, SA *pcliaddr, socklen_t clilen)
{ int n;
socklen_t len;
char mesg[MAXLINE];
for ( ; ; ) {
len = clilen;
n = recvfrom(sockfd, mesg, MAXLINE, 0, pcliaddr, &len);
sendto(sockfd, mesg, n, 0, pcliaddr, len); } }

Code:
//udpcli01.c
#include "unp.h"
#include "sys/socket.h"
#include "string.h"
#include "stdio.h"
#include "stdlib.h"
#include "arpa/inet.h"
#include "netdb.h"
int
main(int argc, char **argv)
{ int sockfd;
struct sockaddr_in servaddr;
if (argc != 2) {
fputs("usage: udpcli <IPaddress>", stderr);
exit(0);
} bzero(&servaddr, sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_port = htons(SERV_PORT);
inet_pton(AF_INET, argv[1], &servaddr.sin_addr);
sockfd = socket(AF_INET, SOCK_DGRAM, 0);
dg_cli(stdin, sockfd, (SA *) &servaddr, sizeof(servaddr));
exit(0);
}

Code:
//udpserv01.c
#include "unp.h"
#include "sys/socket.h"
#include "string.h"
#include "stdio.h"
#include "stdlib.h"
#include "arpa/inet.h"
#include "netdb.h"

int
main(int argc, char **argv)
{ int sockfd;
struct sockaddr_in servaddr, cliaddr;
sockfd = socket(AF_INET, SOCK_DGRAM, 0);
bzero(&servaddr, sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
servaddr.sin_port = htons(SERV_PORT);
bind(sockfd, (SA *) &servaddr, sizeof(servaddr));
dg_echo(sockfd, (SA *) &cliaddr, sizeof(cliaddr));
}

Code:
//unp.h
#include "sys/socket.h"
#include <stdio.h>
#define MAXLINE 4096
/* max text line length */
#define SERV_PORT 9877
#define SA struct sockaddr
void dg_cli(FILE *, int, const SA *, socklen_t);
void dg_echo(int, SA *, socklen_t);