U_SERVER

/*
 * uclient.c
 *
 *  Created on: Mar 14, 2013
 *      Author: none
 */

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


#define     PORT    3666

void die(const char *type_error){
    printf("Error \"%s\" in %s\n", strerror(errno), type_error);
    exit(1);        //Remember: exit doesn't terminate current function but the entire program (closing and saving each file descriptor).
}

size_t  get_file_len(int fd){
    size_t  len;

    lseek(fd, 0, SEEK_SET);             //set at the beginning of your file
    len = lseek(fd, 0, SEEK_END);   //lseek() returns number of byte measured
    lseek(fd, 0, SEEK_SET);         //set again at the beginning of the file

    return len;
}

int main (){

    //define most important socket memebers

    int                 server_fd;      //server file descriptor
    struct sockaddr_in  server, client;
    socklen_t           addr_size;      //

    int     fd;                         //your file descriptor
    char    buff[64];
    char    file_name[32];

    size_t  file_len, size_to_send;

    //CREATE SOCKET
    if ( (server_fd = socket(PF_INET, SOCK_DGRAM, 0)) < 0){
        die("socket()");
    }
    puts("socket()");

    //INITIALIZE SERVER ADDRESS
    server.sin_family       = AF_INET;
    server.sin_port         = htons(PORT);
    server.sin_addr.s_addr  = INADDR_ANY;

    puts("address initialized");

    //BIND ADDRESS AND SOCKET FILE DESCRIPTOR
    addr_size = sizeof(struct sockaddr);
    if ( (bind(server_fd, (struct sockaddr*)&server, addr_size)) < 0){
        die("bind()");
    }
    puts("bind()");

    //RECV FROM CLIENT NAME OF THE FILE YOU WANT TO OPEN
    if ( (recvfrom(server_fd, file_name, sizeof(file_name), 0, (struct sockaddr*)&client, &addr_size)) < 0){
        die("recvfrom");
    }
    printf("Connected with %s at %d port\n", inet_ntoa(client.sin_addr), htons(client.sin_port));

    //OPEN YOUR FILE (IF IT EXISTS) AND THEN CALCULATE IT'S LENGTH AND SEND IT
    if ( (fd = open(file_name, O_RDONLY)) < 0){
        die("open()");
    }
    puts("file opened");

    //GET FILE LEN
    file_len = get_file_len(fd);

    //SEND FILE LENGTH
    if ( (sendto(server_fd, &file_len, sizeof(file_len), 0, (struct sockaddr*)&client, addr_size)) <0 ){
        die("sendto()");
    }
    puts("file length sent");

    //NOW SEND YOUR FILE
    //READ FROM YOUR FILE (fd) AND SAVE sizeof(buff) BYTES TO BUFF
    read(fd, buff, sizeof(buff));
    if ( (size_to_send = sendto(server_fd, buff, strlen(buff), 0, (struct sockaddr*)&client, addr_size)) <0 ){
        die("sendto()");
    }
    puts("file sent");

    //YOUR FILE SHOULD HAVE BEEN SENT SUCCESSFULLY

    return EXIT_SUCCESS;
}