| crazystudentc |
10-24-2012 04:51 AM |
Server/Client Go-Back-N
Hi, I have a little side project I have to do, but for the life of me I cant figure out the information.
Ive got the following two source codes
Server1.c
Code:
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <time.h>
#define MYPORT "4951"
// This is the size of our receiving buffer
#define MAXBUFLEN 100
int main(void)
{
int sockfd;
struct addrinfo hints, *servinfo, *p;
int rv;
int numbytes;
struct sockaddr_storage their_addr;
char buf[MAXBUFLEN];
socklen_t addr_len;
memset(&hints, 0, sizeof hints);
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_DGRAM;
hints.ai_flags = AI_PASSIVE;
// COMMENT -- What does the following function do?
// COMMENT -- Why is the first parameter to getaddrinfo NULL?
if ((rv = getaddrinfo(NULL, MYPORT, &hints, &servinfo)) != 0) {
fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
return 1;
}
for(p = servinfo; p != NULL; p = p->ai_next)
{
if ((sockfd = socket(p->ai_family, p->ai_socktype,
p->ai_protocol)) == -1) {
perror("listener: socket");
continue;
}
if (bind(sockfd, p->ai_addr, p->ai_addrlen) == -1) {
close(sockfd);
perror("listener: bind");
continue;
}
break;
} // END FOR
if (p == NULL) {
fprintf(stderr, "listener: failed to bind socket\n");
return 2;
}
freeaddrinfo(servinfo);
printf("server: waiting to recvfrom...\n");
while(1)
{
addr_len = sizeof their_addr;
if ((numbytes = recvfrom(sockfd, buf, MAXBUFLEN-1 , 0,
(struct sockaddr *)&their_addr, &addr_len)) == -1)
{
perror("recvfrom");
exit(1);
}
buf[numbytes] = '\0';
printf("server: received... \"%s\"\n", buf);
} // END WHILE -- the main loop
// -----------------------------------------------------------------------
// Close the socket to the channel.
close(sockfd);
return 0;
}
and client1.c
Code:
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <time.h>
// The channel's port
#define CHANNELPORT "4950"
// Our receiving buffer length
#define MAXBUFLEN 100
// Size of our frame
#define MAXMESGLEN 1
int main(int argc, char *argv[])
{
int sockfd;
struct addrinfo hints, *servinfo, *p;
int rv;
int numbytes;
socklen_t addr_len;
struct sockaddr_storage their_addr;
char buf[MAXBUFLEN];
char myframe[MAXMESGLEN];
char *mesg = "A"; // Message to be sent
fd_set fds;
int rc;
struct timeval timeout;
memset(&hints, 0, sizeof hints);
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_DGRAM;
if ((rv = getaddrinfo("127.0.0.1", CHANNELPORT, &hints, &servinfo)) != 0) {
fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
return 1;
}
for(p = servinfo; p != NULL; p = p->ai_next)
{
if ((sockfd = socket(p->ai_family, p->ai_socktype,
p->ai_protocol)) == -1) {
perror("client: socket");
continue;
}
break;
}
if (p == NULL) {
fprintf(stderr, "client: failed to bind socket\n");
return 2;
}
myframe[0] = mesg[0];
if ((numbytes = sendto(sockfd, myframe, MAXMESGLEN, 0,
p->ai_addr, p->ai_addrlen)) == -1)
{
perror("talker: sendto");
exit(1);
}
printf("Done Sending: %d\n", numbytes);
freeaddrinfo(servinfo);
close(sockfd);
return 0;
}
Basically I have this code compiled, all works, Im using IdealChannel and EvilChannel, which are two channels im meant to test things on.
In My first step which im stuck on, is I need to modify the above codes to include Go-Back-N. I have to transfer the letters in the char *mesg = "A", and I also have to edit char* mesg so it send a string of ABCD, but sending one letter at a time, and transfer the letters using go-back-n as well.
I was wondering how exactly am I supposed to do that, and how do I then calculate the average round Trip Time of the channel.
I really want to understand this, as then it will help me in the future with my actaul assignments as i know similar things will be coming up soon.
Regards |
