client.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/wait.h>
#include <signal.h>
#include <netdb.h>
#include <pthread.h>
#include <time.h>
#define MAXBUF 1024
#define packetSize 256
#define payloadSize 248
#define headerSize 8

char input[MAXBUF];
int udpSocket;
int returnStatus;
int addrlen;
int clientId;
int windowSize;
int totalNumPackets;
int numAcksSent = 0;
int numNacksSent = 0;
struct sockaddr_in udpClient, udpServer;
char buf[MAXBUF];
char username[256];
char password[256];
char filename[256];
char header[headerSize];
char *dataBuffer = NULL;
char packetBuffer[packetSize];
char payloadBuffer[payloadSize];
int *ackList = NULL;
FILE *outFP;

int main(int argc, char* argv[]) {

    if (argc < 5) {
        fprintf(stderr, "Usage: %s <ip address> <port> <input filename> <output filename>\n", argv[0]);
        exit(1);
    }

    /* create a socket */
    udpSocket = socket(AF_INET, SOCK_DGRAM, 0);
    if (udpSocket == -1) {
        fprintf(stderr, "Could not create a socket!\n");
        exit(1);
    } else {
        printf("Socket created.\n");
    }

    /* client address */
    /* use INADDR_ANY to use all local addresses */
    udpClient.sin_family = AF_INET;
    udpClient.sin_addr.s_addr = INADDR_ANY;
    udpClient.sin_port = 0;
    returnStatus = bind(udpSocket, (struct sockaddr*)&udpClient, sizeof(udpClient));

    if (returnStatus == 0) {
        fprintf(stderr, "Bind completed!\n");
    } else {
        fprintf(stderr, "Could not bind to address!\n");
        close(udpSocket);
        exit(1);
    }

    /* server address */
    /* use the command-line arguments */
    udpServer.sin_family = AF_INET;
    udpServer.sin_addr.s_addr = inet_addr(argv[1]);
    udpServer.sin_port = htons(atoi(argv[2]));

    printf("Welcome!\n");

    // authentication loop
    while(1) {
        printf("Please enter your username: ");
        scanf("%s", username);

        printf("Please enter your password: ");
        scanf("%s", password);

        // send username
        returnStatus = sendto(udpSocket, username, strlen(username)+1, 0,
            (struct sockaddr*)&udpServer, sizeof(udpServer));

        if (returnStatus == -1) {
            fprintf(stderr, "Could not send username!\n");
            exit(1);
        }
        printf("Username sent.\n");

        // send password
        returnStatus = sendto(udpSocket, password, strlen(password)+1, 0,
            (struct sockaddr*)&udpServer, sizeof(udpServer));

        if (returnStatus == -1) {
            fprintf(stderr, "Could not send password!\n");
            exit(1);
        }
        printf("Password sent.\n");

        /* message sent: look for confirmation */
        addrlen = sizeof(udpServer);
        returnStatus = recvfrom(udpSocket, buf, MAXBUF, 0, (struct sockaddr*)&udpServer, &addrlen);
        if (returnStatus == -1) {
           fprintf(stderr, "Did not receive confirmation!\n");
           continue;
        }
        printf("Received: %s\n", buf);
        if(!strcmp(buf, "0")) {
            printf("Authentication failed. Try again.\n");
            continue;
        }
        printf("Authenticated.\n");
        break;
    }

    // file loop
    int isFirst = 1;
    while(1) {

        // get filename from stdin or command line
        if(!isFirst) {
            printf("Please enter your filename: ");
            scanf("%s", filename);
        } else { strcpy(filename, argv[3]); }
        isFirst = 0;

        // send filename
        returnStatus = sendto(udpSocket, filename, strlen(filename)+1, 0,
            (struct sockaddr*)&udpServer, sizeof(udpServer));
        if (returnStatus == -1) {
            fprintf(stderr, "Could not send filename!\n");
            continue;
        }
        printf("Sent request for file: %s.\n", filename);

        // receive confirmation from server
        returnStatus = recvfrom(udpSocket, buf, MAXBUF, 0, (struct sockaddr*)&udpServer, &addrlen);
        if (returnStatus == -1) {
           fprintf(stderr, "Did not receive file confirmation!\n");
           continue;
        }
        printf("Received: %s\n", buf);
        if(!strcmp(buf, "0")) {
            printf("File retrieve failed.\n");
            continue;
        }
        printf("File found.\n");
        break;
    }

    // receive window size
    returnStatus = recvfrom(udpSocket, buf, MAXBUF, 0, (struct sockaddr*)&udpServer, &addrlen);
    windowSize = atoi(buf);
    printf("Window size: %d\n", windowSize);

    // receive expected number of packets
    returnStatus = recvfrom(udpSocket, buf, MAXBUF, 0, (struct sockaddr*)&udpServer, &addrlen);
    totalNumPackets = atoi(buf);
    printf("Number of packets: %d\n", totalNumPackets);

    // allocate memory for whole file
    dataBuffer = (char*) malloc(sizeof(char)*packetSize*totalNumPackets);
    ackList = (int*) malloc(sizeof(int)*totalNumPackets);
    for(int i = 0; i < totalNumPackets; i++) { ackList[i] = 0; }

    while(1) {
        // check if all packets received
        int yesCount = 0;
        for(int i = 0; i < totalNumPackets; i++) {
            if(ackList[i] == 1) yesCount++;
        }
        if(yesCount == totalNumPackets) {
            printf("Whole file received!!\n");
            break;
        }

        // receive packet
        printf("Waiting for packet...\n");
        returnStatus = recvfrom(udpSocket, packetBuffer, packetSize, 0, (struct sockaddr*)&udpServer, &addrlen);

        // strip header
        strncpy(header, packetBuffer, headerSize);
        int receivedPacket = atoi(header);
        printf("Received packet: %d\n", receivedPacket);

        // strip payload
        strncpy(payloadBuffer, &packetBuffer[headerSize], payloadSize);
        // printf("%s\n", payloadBuffer);

        // build response
        char response[headerSize+3] = "ACK";
        strcat(response, header);
        printf("%s\n", response);

        // store packet and confirm receipt
        ackList[receivedPacket] = 1;
        strncpy(&dataBuffer[receivedPacket*payloadSize], payloadBuffer, payloadSize);
        returnStatus = sendto(udpSocket, response, strlen(response)+1, 0,
            (struct sockaddr*)&udpServer, sizeof(udpServer));
        numAcksSent++;
    }

    // write to file
    outFP = fopen(argv[4], "w");
    fputs(dataBuffer, outFP);
    fclose(outFP);

    // calc date
    time_t t = time(NULL);
    struct tm *tm = localtime(&t);
    char time[64];
    strftime(time, sizeof(time), "%c", tm);

    printf("\n=== METRICS ===\n");
    // Name and Size of the file that was received
    printf("Received file '%s' (%d bytes)\n", filename, (int)strlen(dataBuffer));
    // File Creation Date & Time
    printf("File created: %s\n", time);
    // Number of Data Packets received
    printf("Packets received: %d\n", totalNumPackets);
    // Number of Acknowledgement Sent
    printf("Sent %d ACKs.\n", numAcksSent);
    // Number of Negative Acknowledgement Sent
    printf("Sent %d NACKs.\n", numNacksSent);

    /* cleanup */
    close(udpSocket);
    free(dataBuffer);
    return 0;
}