In the C programming language, how should I go about writing two programs (sende
ID: 3808791 • Letter: I
Question
In the C programming language, how should I go about writing two programs (sender & reciever) which create a reliable communication protocol to demonstrate reliable unicast using UDP? The sender program runs on one host and reads data files as input, and breaks the contents into UDP datagrams. The receiver should simulate unreliable communication by randomly dropping a percentage of incoming packets. Acknowledgements, retransmission, packet resequencing, and timeouts should all be taken into consideration.
Explanation / Answer
Basically the requirement of the given question leads to chat application. So in this section we will design a chat application using UDP for reliable communication.
Here is the code:
SERVER
#include<stdio.h>
#include<netinet/in.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<netdb.h>
#include<string.h>
#include<stdlib.h>
#define MAX 80
#define PORT 43454
#define SA struct sockaddr
void func(int sockfd)
{
char buff[MAX];
int n,clen;
struct sockaddr_in cli;
clen=sizeof(cli);
for(;;)
{
bzero(buff,MAX);
recvfrom(sockfd,buff,sizeof(buff),0,(SA *)&cli,&clen);
printf("From client %s To client",buff);
bzero(buff,MAX);
n=0;
while((buff[n++]=getchar())!=' ');
sendto(sockfd,buff,sizeof(buff),0,(SA *)&cli,clen);
if(strncmp("exit",buff,4)==0)
{
printf("Server Exit... ");
break;
}
}
}
int main()
{
int sockfd;
struct sockaddr_in servaddr;
sockfd=socket(AF_INET,SOCK_DGRAM,0);
if(sockfd==-1)
{
printf("socket creation failed... ");
exit(0);
}
else
printf("Socket successfully created.. ");
bzero(&servaddr,sizeof(servaddr));
servaddr.sin_family=AF_INET;
servaddr.sin_addr.s_addr=htonl(INADDR_ANY);
servaddr.sin_port=htons(PORT);
if((bind(sockfd,(SA *)&servaddr,sizeof(servaddr)))!=0)
{
printf("socket bind failed... ");
exit(0);
}
else
printf("Socket successfully binded.. ");
func(sockfd);
close(sockfd);
}
CLIENT
#include<sys/socket.h>
#include<netdb.h>
#include<string.h>
#include<stdlib.h>
#include<stdio.h>
#define MAX 80
#define PORT 43454
#define SA struct sockaddr
int main()
{
char buff[MAX];
int sockfd,len,n;
struct sockaddr_in servaddr;
sockfd=socket(AF_INET,SOCK_DGRAM,0);
if(sockfd==-1)
{
printf("socket creation failed... ");
exit(0);
}
else
printf("Socket successfully created.. ");
bzero(&servaddr,sizeof(len));
servaddr.sin_family=AF_INET;
servaddr.sin_addr.s_addr=inet_addr("127.0.0.1");
servaddr.sin_port=htons(PORT);
len=sizeof(servaddr);
for(;;)
{
printf(" Enter string : ");
n=0;
while((buff[n++]=getchar())!=' ');
sendto(sockfd,buff,sizeof(buff),0,(SA *)&servaddr,len);
bzero(buff,sizeof(buff));
recvfrom(sockfd,buff,sizeof(buff),0,(SA *)&servaddr,&len);
printf("From Server : %s ",buff);
if(strncmp("exit",buff,4)==0)
{
printf("Client Exit... ");
break;
}
}
close(sockfd);
}
Sample Output Section
SERVER SIDE
$ cc udpchatserver.c
$ ./a.out
Socket successfully created..
Socket successfully binded..
From client hai
To client hello
From client exit
To client exit
Server Exit...
$
CLIENT SIDE
$ cc udpchatclient.c
$ ./a.out
Socket successfully created..
Enter string : hai
From Server : hello
Enter string : exit
From Server : exit
Client Exit...
$