S01_BSD_04_SERVER

/*
Napisz programy przesyłające plik o wielkości przekraczającej 1 MiB między
dwoma komputerami, przy użyciu protokołu bezpołączeniowego.
*/

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <fcntl.h>
#include <string.h>
#include <unistd.h>

#define FILENAME "received_file"
#define SERVER_PORT 1919
#define END_FLAG "--END_OF_TRANSFER--"

void error_handler(const char *msg)
{
    perror(msg);
    exit(EXIT_FAILURE);
}

int main(void)
{
    int sockfd, filefd;
    struct sockaddr_in sockaddr;
    char buffer[BUFSIZ];
    int remain_bytes;
    ssize_t received_bytes;

    sockaddr.sin_family = AF_INET;
    sockaddr.sin_port = htons(SERVER_PORT);
    sockaddr.sin_addr.s_addr = INADDR_ANY;
    memset(sockaddr.sin_zero, '\0', 8);

    if((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1)
        error_handler("socket");

    if(bind(sockfd, (struct sockaddr *)&sockaddr, sizeof(sockaddr)) == -1)
        error_handler("bind");

    printf("Oczekiwanie na przeslanie pliku...\n");

    socklen_t socklen = sizeof(struct sockaddr);
    if(recvfrom(sockfd, buffer, BUFSIZ, 0, (struct sockaddr *)&sockaddr, &socklen) == -1)
        error_handler("recvfrom");
    remain_bytes = atoi(buffer);

    printf("Przesylanie pliku o rozmiarze %d bajtow...\n", remain_bytes);

    if((filefd = open(FILENAME, O_RDWR | O_CREAT, 0755)) == -1)
        error_handler("open");

    memset(buffer, '\0', BUFSIZ);

    for(;;) {
        memset(buffer, '\0', BUFSIZ);
        if((received_bytes = recvfrom(sockfd, buffer, BUFSIZ, 0, (struct sockaddr *)&sockaddr, &socklen)) == -1)
            error_handler("recvfrom");

        if(!strcmp(END_FLAG, buffer))
            break;
        if(write(filefd, buffer, BUFSIZ) == -1)
            error_handler("write");
    }

    printf("Plik zostal odebrany!\n");

    if((close(sockfd) == -1) || ((close(filefd)) == -1))
        error_handler("close");

    return EXIT_SUCCESS;
}