destination.cpp

#include <iostream>
#include <cstring>
#include <pthread.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <cstdlib>
#include <ctime>
#include <unistd.h>
#include "packet.h"
using namespace std;

void error(char *msg) 
{
    perror(msg);
    exit(1);
}

void errorMsg(char *msg)
{
    cout<<endl;
    cout<<"Invalid input(s)..."<<endl;
    cout<<"Correct format:"<<endl;
    cout<<"<portno> port number."<<endl;
    cout<<endl;
    exit(1);
}

int main(int argc, char *argv[]) 
{
    
    //socket stuff
    int sockfd, portno;
    socklen_t clilen;
    struct sockaddr_in svrAddr, cliAddr;
    char *buf;

    //additional variables for project 3
    float b = 5;
    double timer = 0;

    cout<<"************************************"<<endl;
    cout<<"*** Welcome to EE 122 Project #2 ***"<<endl;
    cout<<"***     Shuo Sun and Gabriel     ***"<<endl;
    cout<<"***        Destination Program   ***"<<endl;
    cout<<"************************************"<<endl; 
    cout<<"(ctrl + c to exit)"<<endl;

    //read from command line
    if (argc != 2 && argc != 3) errorMsg("Invalid input format"); 

    portno = atoi(argv[1]);
    if(portno > 65535 || portno < 0) error("Port number must be between 0 - 65535");
    cout<<"Port number: "<<portno<<endl;

    //initialize program
    cout<<"Starting client..."<<endl;
    cout<<"Creating listening socket...";
    sockfd = socket(AF_INET, SOCK_DGRAM, 0);
    if (sockfd < 0) error("Unable to create socket.");
    cout<<"Done"<<endl;

    cout<<"Binding socket to port...";
    bzero((char *) &svrAddr, sizeof(svrAddr));
    svrAddr.sin_family = AF_INET;
    svrAddr.sin_addr.s_addr = INADDR_ANY;
    svrAddr.sin_port = htons(portno);
    if(::bind(sockfd, (struct sockaddr *)&svrAddr, sizeof(svrAddr)) < 0) error("Unable to bind socket to port.");
    cout<<"Done"<<endl;

    cout<<"Initializing receiver...Done"<<endl;
    cout<<"Initializing buffer..."<<endl;
    buf = new char[MAX_PACKET_SIZE];
    int count = 1;

    struct timeval tv;
    int delaySum = 0;
    //----------------------
    //project 3 delay
    struct timeval start;
    struct timeval end;
    socklen_t alen;
    struct sockaddr_in ackAddr;
    struct hostent *ack;   
    int saved = 0;
    //----------------------

   while(1) 
    {
        /////////////////////////
        // project 3
        gettimeofday(&start,NULL);
        int randomDelay = rand()%(int)(b * 1000);
        float randomDelay2 = (float)randomDelay/1000;
        if(argc==3 && strcmp(argv[2], "-D")==0){
        //if destination is D2 then add random delay
        usleep(randomDelay2);
        }
        //////////////////////////
        
        cout<<"Receiving Packet "<< count <<endl;
        int n = recvfrom(sockfd, buf, MAX_PACKET_SIZE, 0, (struct sockaddr *)&cliAddr, &clilen);
        count += 1;
        //cal delay
        gettimeofday(&tv, NULL);
        unsigned long long msSinceEpoch =
                (unsigned long long)(tv.tv_sec) * 1000 +
                    (unsigned long long)(tv.tv_usec) / 1000;

        packet *p = (packet *)buf;
        unsigned long long msSinceEpoch2 =
                (unsigned long long)(p->tv.tv_sec) * 1000 +
                    (unsigned long long)(p->tv.tv_usec) / 1000;

        unsigned long long delay = msSinceEpoch - msSinceEpoch2;
        //cout<<delay<<endl;
        delaySum += delay;
        //cout<<delaySum<<endl;
        
        //project 3 - send back ACKs
        //construct ACK packet
        packet *pkt = (packet *) malloc(sizeof(packet));
        memcpy(pkt, buf, MAX_PACKET_SIZE);
        ackpacket p2;  
        p2.sequenceNumber = pkt->sequenceNumber;
        p2.tv = pkt->tv;
        
        //send back ack

        if(!saved){
        ack = gethostbyname(pkt->sourceIP);
        bzero((char *) &ackAddr, sizeof(ackAddr));
        ackAddr.sin_family = AF_INET;
        ackAddr.sin_port = htons(pkt->sourcePort);
        bcopy((char *)ack->h_addr,
                (char *)&ackAddr.sin_addr.s_addr,
                ack->h_length);
        alen = sizeof(ackAddr);
        saved = 1;
        }
        if(sendto(sockfd, &p2, MAX_PACKET_SIZE, 0, (struct sockaddr *)&ackAddr, alen)==-1) error("Unable to send packet");
        cout<<"ACK sent to "<<pkt->sourceIP<<":"<<pkt->sourcePort<<endl;

    //-------------------------
    //project 3 delay
    gettimeofday(&end, NULL);
    unsigned long long s_time = (unsigned long long)(start.tv_sec)*1000 + (unsigned long long)(start.tv_usec)/1000;

unsigned long long e_time = (unsigned long long)(end.tv_sec)*1000 + (unsigned long long)(end.tv_usec)/1000;

    double duration = (double) (e_time - s_time) / 1000;
    timer += duration;

    if(timer > 5) {
        if(b == 5) b = 15;
        else b = 5;
        timer = 0;
    }
    //cout<<timer<<"("<<b<<")"<<endl;
    //------------------------

    }
    return 0;
}