7. Write a program using UDP Sockets to enable file transfer (Script, Text, Audio and Video one file each) between two machines. Demonstrate the packets captured traces using Wireshark Packet Analyzer Tool for peer to peer mode.

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Client.c

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<arpa/inet.h>
#include<sys/socket.h>

#define SERVER "127.0.0.1"
#define BUFLEN 503
#define PORT 8885

void die(char *s)// used to quit
{
perror(s);
exit(1);
}
unsigned long fsize(char* file)
{
    FILE * f = fopen(file, "r");
    fseek(f, 0, SEEK_END);//used to take the function pointer to the starting of the file or end of the file or to    any position specified by the user.
    unsigned long len = (unsigned long)ftell(f);// used to find out the position of file pointer in the file with respect to starting of the file.
    fclose(f);
    return len;
}

int main(void)
{
struct sockaddr_in si_other;
int s, i, slen=sizeof(si_other);
char buf[BUFLEN];
char message[BUFLEN];

if ( (s=socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) == -1)
{
die("socket");
}

memset((char *) &si_other, 0, sizeof(si_other));

si_other.sin_family = AF_INET;
si_other.sin_port = htons(PORT);

if (inet_aton(SERVER , &si_other.sin_addr) == 0) //converts the specified string, in the Internet standard dot notation, to a network address, and stores the address in the structure provided.
{
fprintf(stderr, "inet_aton() failed\n");
exit(1);
}

char fname[20];
printf("Enter Filename with extension: ");
scanf("%s",&fname);//add.txt
sendto(s, fname, 20 , 0 , (struct sockaddr *) &si_other, slen);
memset(message,0,503);
unsigned long siz = fsize(fname);//fsize(add.txt)=20
printf("%ld",(siz % 503));//20%503=20
char str[10];
sprintf(str, "%d", siz);
sendto(s, str, 20 , 0 , (struct sockaddr *) &si_other, slen);
FILE *f;
f=fopen(fname,"rb");
memset(message,0,503);
fread(message, 503,1,f);
int itr =1;
while(itr*503<siz)
{
//fread(message, 503,1,f);
if (sendto(s, message, 503 , 0 , (struct sockaddr *) &si_other, slen)==-1)
{
die("sendto()");
}
memset(message,0,503);
fread(message, 503,1,f);
itr++;
}
fread(message, (siz % 503),1,f);
sendto(s, message, (siz % 503) , 0 , (struct sockaddr *) &si_other, slen);
memset(message,0,503);
fclose(f);
close(s);
return 0;
}

Server.c

#include<stdio.h>

#include<string.h>

#include<stdlib.h>

#include<arpa/inet.h>

#include<sys/socket.h>

#define BUFLEN 503

#define PORT 8885

void die(char *s)

{

perror(s);

exit(1);

}

int main(void)

{

struct sockaddr_in si_me, si_other;

int s, i,j, slen = sizeof(si_other) , recv_len;

char buf[BUFLEN];

if ((s=socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) == -1)

{

die("socket");

}

memset((char *) &si_me, 0, sizeof(si_me));

si_me.sin_family = AF_INET;

si_me.sin_port = htons(PORT);

si_me.sin_addr.s_addr = htonl(INADDR_ANY);

if( bind(s , (struct sockaddr*)&si_me, sizeof(si_me) ) == -1)

{

die("bind");

}

char fname[20];

FILE *fp;

recv_len = recvfrom(s, buf, 20, 0, (struct sockaddr *) &si_other, &slen);

char fna[100];

memset(buf,0,503);

recv_len = recvfrom(s, buf, 20, 0, (struct sockaddr *) &si_other, &slen);

strcpy(fna,buf);

int len= strlen(fna);

printf("%d",len);//20

for(j=len-1;j>=0;j--)

{

if(fna[j]=='.')

{

fna[j-1]='1';

}

}

unsigned long mm = atoi(buf);

fp=fopen(fna,"wb");

int itr=1;

memset(buf,0,503);

while(itr*503<mm)

{

if ((recv_len = recvfrom(s, buf, 503, 0, (struct sockaddr *) &si_other, &slen)) == -1)

{

die("recvfrom()");

}

fwrite(buf,503, 1, fp);

memset(buf,0,503);

itr++;

}

printf("%d",(mm%503));

recv_len = recvfrom(s, buf, (mm%503), 0, (struct sockaddr *) &si_other, &slen);

fwrite(buf,(mm%503), 1, fp);

memset(buf,0,503);

fclose(fp);

close(s);

return 0;

}