path: root/server.c

#include <stdlib.h>
#include <pthread.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <string.h>

#include <sys/stat.h>
#include <fcntl.h>
#include <sys/types.h>

#include "protocol.c"

#define LINE_MAX 1024
#define MAX_USERS 1000
#define MAX_PATH 50
#define MAX_RATE_PER_SECOND 16*1024

// typedef struct station {
//     int streamFd;
//     char* filePath;
//     int fileBufferSize;
//     char fileBuffer[MAX_STREAM_RATE];
// } station_t;
typedef struct station {
    pthread_t streamThread;
    int readfd;
    char *filePath;
} station_t;
int num_stations;
station_t *stations;
int setup_stations(int argc, char *argv[]);
void *stream_routine(void *arg);


typedef struct user {
    int udpPort;
    int stationNum;
    int sockfd;
} user_t;


/* For safe condition variable usage, must use a boolean predicate and  */
/* a mutex with the condition.                                          */
int                 count = 0;
pthread_cond_t      cond  = PTHREAD_COND_INITIALIZER;
pthread_mutex_t     mutex = PTHREAD_MUTEX_INITIALIZER;

pthread_mutex_t     station_mutex = PTHREAD_MUTEX_INITIALIZER;

const char *port;
// int num_stations;

int start_threads = 0;
int max_active_users = 0;
int max_sockfd = 0;

pthread_mutex_t     mutex_user_data = PTHREAD_MUTEX_INITIALIZER;
// array from index to user_data
user_t  *user_data;
int *sockfd_to_user;

// stations array pointer
// station_t *station_data;

struct udp_packet_routine_args {
    int user_index;
    int buffer_size;
    char *file_buffer;
};

void *send_udp_packet_routine(void* arg);
void *select_routine(void* arg);
void *sync_routine(void* arg);
void *send_announce_routine(void* arg);

void init_station(int station_num, const char *station_name);

int parse(char buffer[LINE_MAX], char *tokens[LINE_MAX / 2]);
void *print_info_routine(void *arg);

void *get_in_addr(struct sockaddr *sa);

void *init_user(int sockfd);
void *update_user_udpPort(int sockfd, int udpPort);
void *update_user_station(int sockfd, int stationNum);
void *print_user_data(int sockfd);
void destroy_user(int sockfd);

void send_announce_reply(int fd, int station_num);
void send_invalid_command_reply(int fd, size_t message_size, char* message);

// void *load_file(void* arg);

main(int argc, char *argv[])
{
    // check and assign arguments
    if (argc < 3) {
        fprintf(stderr,"usage: ./snowcast_server <listen port> <file0> [file 1] [file 2] ... \n");
        exit(1);
    }

    // initizlize the port
    port = argv[1];

    // initialize the stations & their threads
    if (setup_stations(argc, argv) == -1) {
        perror("setup_stations");
        exit(1);
    }

    // make array of user data
    printf("max active users: %d\n", sizeof(user_t) * max_active_users);
    user_data = malloc(sizeof(user_t) * max_active_users);
    if (!user_data) {  perror("malloc userdata"); return 1; }
    sockfd_to_user = malloc(sizeof(int) * max_active_users);
    if (!sockfd_to_user) {  perror("malloc sockfd to user"); return 1; }

    // make and start "select" thread that manages:
    // 1) new connections, 2) requests from current connections, 3) closing connections
    pthread_t select_thread;
    pthread_create(&select_thread, NULL, select_routine, NULL);

    // start syncchronization thread to broadcast stations
    // pthread_t sync_thread;
    // pthread_create(&sync_thread, NULL, sync_routine, NULL);

    // command line interface
    char input[LINE_MAX];
    memset(input, 0, LINE_MAX);

    char *tokens[LINE_MAX / 2];
    while (read(STDIN_FILENO, input, LINE_MAX) > 0) {
        // init tokens
        memset(tokens, 0, (LINE_MAX / 2) * sizeof(char *));

        // if 0, all whitespace
        if (!parse(input, tokens))
            continue;

        char *command = tokens[0];
        // if q, shutdown!
        if (!strcmp(command, "q")) {
            printf("Exiting.\n");
            // TODO: exit better than break
            break;
        }
        
        // if p, print info
        else if (!strcmp(command, "p")) {
            // get the file descriptor
            int print_fd = 0;
            // see if there is a file path
            char *output_file_path = tokens[1];
            if (output_file_path != NULL)
            {
                if ((print_fd = open(output_file_path, O_CREAT | O_WRONLY | O_TRUNC, S_IRWXU)) == -1)
                {
                    perror("open");
                    continue;
                }
            } else {
                print_fd = STDOUT_FILENO;
            }
            // printf("print_fd: %d\n", print_fd);
            pthread_t print_info_thread;
            pthread_create(&print_info_thread, NULL, print_info_routine, print_fd);
            // note - this file descriptor is closed in the thread
        }
        else if (!strcmp(command, "u"))
        {
            // print all user data
            for (int i = 0; i < max_active_users; i++)
            {
                print_user_data(i);
            }
        }
    }

    return 0;
}

int read_file(int fd, char buffer[MAX_RATE_PER_SECOND], int station_num) {
    int bytes_read = read(fd, buffer, MAX_RATE_PER_SECOND);
    if (bytes_read < 0) { perror("read (from station file)"); return -1; }
    // printf("bytes read: %d\n", bytes_read);
    if (bytes_read == 0) {
        // printf("end of file, restarting\n");
        pthread_t send_announce_thread;
        pthread_create(&send_announce_thread, NULL, send_announce_routine, station_num);

        if (lseek(fd, 0, SEEK_SET) == -1)
        {
            perror("lseek (in resarting file)");
            return -1;
        }
        bytes_read = read(fd, buffer, MAX_RATE_PER_SECOND);
        if (bytes_read < 0) { perror("read (from station file, after restart)"); return -1; }
    }

    return bytes_read;
}

void *stream_routine_cleanup(void *arg) {
    int read_fd = (int) arg;
    close(read_fd);
}

void *stream_routine(void *arg) {
    int station_num = (int) arg;
    printf("stream routine %d\n", station_num);
    int read_fd = stations[station_num].readfd;

    pthread_cleanup_push(stream_routine_cleanup, read_fd);

    // make buffer which will be used to stream to children
    char buffer[MAX_RATE_PER_SECOND];
    memset(buffer, 0, MAX_RATE_PER_SECOND);
    // if (!buffer) { perror("malloc (buffer in station thread)"); exit(1); }

    for (;;)
    {
        // load bytes into buffer
        int bytes_read = read_file(read_fd, buffer, station_num);
        if (bytes_read == -1) { exit(1); }

        // TODO: send buffer to children
        char *send_buffer = malloc(2 + bytes_read);
        for (int i = 0; i < max_active_users; i++)
        {
            if (!user_data[i].sockfd || user_data[i].sockfd == -1)
                continue;
            if (user_data[i].stationNum == station_num)
            {
                // send the udp packet
                int *send_buffer = malloc(2 + bytes_read);
                memset(send_buffer, 0, 2 + bytes_read);
                send_buffer[0] = i;
                send_buffer[1] = bytes_read;
                memcpy(send_buffer+2, buffer, bytes_read);
                // printf("sending udp packet to user %d\n", i);
                pthread_t t;
                pthread_create(&t, NULL, send_udp_packet_routine, send_buffer);
            }
        }
        free(send_buffer);
        usleep(1000000-5000);
        start_threads = 1;
        pthread_cond_broadcast(&cond);

        usleep(5000);
        start_threads = 0;

        memset(buffer, 0, MAX_RATE_PER_SECOND);
    }

    return (NULL);

    pthread_cleanup_pop(1);
}

int setup_stations(int argc, char *argv[]) {
    num_stations = argc - 2;

    // get the size to malloc
    int totalSize = 0;
    for(int i = 2; i < argc; i++)
    {
        totalSize += sizeof(pthread_t) + sizeof(int)  + strlen(argv[i]);
    }

    // malloc the stations array
    stations = malloc(totalSize);
    if (!stations) { perror("malloc (stations pointer)"); return -1; }
    // assign the stations, and start the threads
    for (int i = 0; i < num_stations; i++) {
        stations[i].filePath = argv[i+2];
        stations[i].readfd = open(argv[i+2], O_RDONLY);
        if (stations[i].readfd < 0) { perror("read (from station file)"); return -1; }
        pthread_create(&stations[i].streamThread, NULL, stream_routine, i);
    }

    printf("successfully created %d stations\n", num_stations);
    return 1;
}

void write_int_to_fd(int fd, int n) {
    int l = snprintf(NULL, 0, "%d", n);
    char *num = malloc(l + 1);
    if (!num) { perror("malloc write to fd"); return; }

    snprintf(num, l + 1, "%d", n);
    if (write(fd, num, strlen(num)) == -1) {
        perror("write");
    }


    free(num);
}

void *print_info_routine(void *arg) {
    int print_fd = (int) arg;
    // printf("thread print_fd: %d\n", print_fd);
    // printf("num_stations: %d\n", num_stations);
    for (int i = 0; i < num_stations; i++) {
        write_int_to_fd(print_fd, i);
        char *comma = ",";
        write(print_fd, comma, strlen(comma));

        // write file path
        char* file_path = stations[i].filePath;
        write(print_fd, file_path, strlen(file_path));

        for (int j = 0; j < max_active_users; j++) {
            if (!user_data[j].sockfd || user_data[j].sockfd == -1)
                continue;
            if (user_data[j].stationNum == i) {
                char *localhost_ip = ",127.0.0.1:";
                write(print_fd, localhost_ip, strlen(localhost_ip));
                // write udpPort
                write_int_to_fd(print_fd, user_data[j].udpPort);
            }
        }
        // wrtie new line
        char *newline = "\n";
        write(print_fd, newline, strlen(newline));
    }

    if (print_fd != STDOUT_FILENO) close(print_fd);
    return (NULL);
}

int send_all_udp(int udp_sockfd, char *buf, int *len, struct addrinfo *thread_res)
{
    int MAX_PACKET_SIZE = 512;
    int total = 0;        // how many bytes we've sent
    int bytesleft = *len; // how many we have left to send
    int n;

    while(total < *len) {
        n = sendto(udp_sockfd, buf+total, MAX_PACKET_SIZE, 0, thread_res->ai_addr, thread_res->ai_addrlen);
        //         thread_res->ai_addr, thread_res->ai_addrlen)) == -1;
        if (n == -1) { break; }
        total += n;
        bytesleft -= n;
    }

    *len = total; // return number actually sent here

    return n==-1?-1:0; // return -1 on failure, 0 on success
} 

void udp_port_cleanup_handler(void *arg)
{
    int sockfd = (int) arg;
    close(sockfd);
}

/* Make the manager routine */
void *send_udp_packet_routine(void *arg) {
    // printf("send udp packet routine\n");
    int *buf =  arg;
    // unpack args
    int user_index = buf[0];
    int buffer_size = buf[1];
    char *file_buffer = malloc(buffer_size);
    memcpy(file_buffer, buf+2, buffer_size);

    // printf("udp packet routine, user:%d\n size: %d\n", user_index, buffer_size);

    // declare vairables to be used
    int did_work = 1;
    pthread_mutex_t m = PTHREAD_MUTEX_INITIALIZER;
    int s;
    int udp_sockfd;
    struct addrinfo thread_hints, *thread_res, *thread_servinfo;
    int error_code;

    // setup hints
    memset(&thread_hints, 0, sizeof thread_hints);
    thread_hints.ai_family = AF_INET;  // use IPv4 only
    thread_hints.ai_socktype = SOCK_DGRAM;
    thread_hints.ai_flags = AI_PASSIVE; // fill in my IP for me

    int int_port = user_data[user_index].udpPort;
    int length = snprintf( NULL, 0, "%d", int_port );
    char* port = malloc( length + 1 );
    if (!port) { perror("malloc on port"); return (NULL); }
    snprintf(port, length + 1, "%d", int_port);
    sprintf(port, "%d", int_port);

    if (error_code = getaddrinfo(NULL, port, &thread_hints, &thread_servinfo) != 0)
    {
        fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(error_code));
        return (NULL);
    }
    free(port);

    // loop through all the results and make a socket
    for(thread_res = thread_servinfo; thread_res != NULL; thread_res = thread_res->ai_next) {
        if ((udp_sockfd = socket(thread_res->ai_family, thread_res->ai_socktype,
                thread_res->ai_protocol)) == -1) {
            perror("talker: socket");
            continue;
        }
        break;
    }
    if (udp_sockfd == NULL) {
        fprintf(stderr, "talker: failed to create socket\n");
        return (NULL);
    }

    pthread_cleanup_push(udp_port_cleanup_handler, (void *)udp_sockfd);
        // wait for 
    pthread_mutex_lock(&m);
    did_work = 0;
    while (!start_threads)
    {
        pthread_cond_wait(&cond, &m);
    }

    int station_num = user_data[user_index].stationNum;
    if (station_num == -1) {
        did_work = 1;
    }
    // potential error here!
    // printf("station info - bytes read: %d, station_fd: %d, filePath: %s, buffersize: %d\n", bytes_read, station_info->streamFd, station_info->filePath, station_info->fileBufferSize);

    if (send_all_udp(udp_sockfd, file_buffer, &buffer_size, thread_res) == -1)
    {
        perror("send_all_udp");
        printf("We only sent %d bytes because of the error!\n", buffer_size);
    }

    free(file_buffer);

    pthread_mutex_unlock(&m);

    pthread_cleanup_pop(1);

    return (NULL);
}

void *send_announce_routine(void *arg) {
    // unpack args
    int station_num = (int) arg;
     // send the announce messages
    for (int i = 0; i < max_active_users; i++)
    {
        if (user_data[i].sockfd == 0 || user_data[i].sockfd == -1) {
            continue;
        }
        // update the station of each user
        if (user_data[i].stationNum == station_num)
        {
            send_announce_reply(user_data[i].sockfd, station_num);
        }
    }
}

// void *sync_routine(void *arg) {
//     int c = 0;
//     while (1)
//     {
//         start_threads = 1;
//         pthread_cond_broadcast(&cond);
//         usleep(2000);

//         start_threads = 0;

//         usleep(1000000-2000);
//     }
// }

void *select_routine(void *arg) {
    fd_set master;    // master file descriptor list
    fd_set read_fds;  // temp file descriptor list for select()
    int fdmax;        // maximum file descriptor number

    int listener;     // listening socket descriptor
    int newfd;        // newly accept()ed socket descriptor
    struct sockaddr_storage remoteaddr; // client address
    socklen_t addrlen;

    char buf[256];    // buffer for client data
    int nbytes;


    char remoteIP[INET6_ADDRSTRLEN];

    int yes=1;        // for setsockopt() SO_REUSEADDR, below
    int i, j, rv;

    struct addrinfo hints, *ai, *p;

    // const char* port = argv[1];

    FD_ZERO(&master);    // clear the master and temp sets
    FD_ZERO(&read_fds);

    // LISTENER: get us a socket and bind it
    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_INET;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_flags = AI_PASSIVE;
    if ((rv = getaddrinfo(NULL, port, &hints, &ai)) != 0) {
        fprintf(stderr, "snowcast_server: %s\n", gai_strerror(rv));
        exit(1);
    }

    for(p = ai; p != NULL; p = p->ai_next) {
        listener = socket(p->ai_family, p->ai_socktype, p->ai_protocol);
        if (listener < 0) { 
            continue;
        }
        
        // lose the pesky "address already in use" error message
        setsockopt(listener, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(int));

        if (bind(listener, p->ai_addr, p->ai_addrlen) < 0) {
            close(listener);
            continue;
        }

        break;
    }

    // if we got here, it means we didn't get bound
    if (p == NULL) {
        fprintf(stderr, "snowcast_server: failed to bind\n");
        exit(2);
    }

    freeaddrinfo(ai); // all done with this

     // listen
    if (listen(listener, 10) == -1) {
        perror("listen");
        exit(3);
    }

    // add the listener to the master set
    FD_SET(listener, &master);

    // keep track of the biggest file descriptor
    fdmax = listener; // so far, it's this one

    while(1) {
        read_fds = master; // copy it
        if (select(fdmax+1, &read_fds, NULL, NULL, NULL) == -1) {
            perror("select");
            exit(4);
        }

        // run through the existing connections looking for data to read
        for(i = 0; i <= fdmax; i++) {
            if (FD_ISSET(i, &read_fds)) { // we got one!!
                if (i == listener) {
                    // handle new connections
                    addrlen = sizeof remoteaddr;
                    newfd = accept(listener,
                        (struct sockaddr *)&remoteaddr,
                        &addrlen);

                    if (newfd == -1) {
                        perror("accept");
                    } else {
                        struct timeval tv;
                        tv.tv_sec = 0;
                        tv.tv_usec = TIMEOUT;
                        if (setsockopt(newfd, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv)) < 0) {
                            perror("setsockopt");
                        }

                        uint8_t command_type = -1;
                        if ((nbytes = recv(newfd, &command_type, 1, 0)) <= 0)
                        {
                            // got error or connection closed by client
                            if (nbytes == 0) {
                                // connection closed
                                // printf("selectserver: socket %d hung up\n", i);
                            } else {
                                perror("recv");
                            }
                            // remove user from data structures
                            close(newfd);
                            // destroy_user(i);
                            continue;
                        }

                        if (command_type != 0) {
                            char * message = "must send a Hello message first";
                            send_invalid_command_reply(newfd, strlen(message), message);
                            close(newfd);
                            continue;
                        }

                         // get the udp port
                        uint16_t udp_port = -1;
                        int bytes_to_read = sizeof(uint16_t);
                        if (recv_all(newfd, &udp_port, &bytes_to_read) == -1) {
                            perror("recv_all");
                            close(newfd);
                            // destroy_user(i);
                            continue;
                        }
                        udp_port = ntohs(udp_port);

                        FD_SET(newfd, &master); // add to master set
                        if (newfd > fdmax) {    // keep track of the max
                            fdmax = newfd;
                        }
                        init_user(newfd);
                        update_user_udpPort(newfd, udp_port);

                         // send the welcome message to client
                        struct Welcome welcome;
                        welcome.replyType = 2;
                        welcome.numStations = htons(num_stations);
                        int bytes_to_send = sizeof(struct Welcome);
                        if (send_all(newfd, &welcome, &bytes_to_send) == -1)
                            perror("send_all");
                }
                } else {
                    // handle data from a client
                    uint8_t command_type = -1;
                    if ((nbytes = recv(i, &command_type, 1, 0)) <= 0)
                    {
                        // got error or connection closed by client
                        if (nbytes == 0) {
                            // connection closed
                            // printf("selectserver: socket %d hung up\n", i);
                        } else {
                            perror("recv");
                        }
                        close(i); // bye!
                        FD_CLR(i, &master); // remove from master set
                        // remove user from data structures
                        destroy_user(i);
                    }
                    else
                    {
                        // we got some data from a client
                        if (command_type == 0) { // we got a Hello commmand

                            // get the udp port
                            uint16_t udp_port = -1;
                            int bytes_to_read = sizeof(uint16_t);
                            if (recv_all(i, &udp_port, &bytes_to_read) == -1) {
                                perror("recv_all");
                                close(i);
                                FD_CLR(i, &master);
                                destroy_user(i);
                                continue;
                            }

                            if (user_data[sockfd_to_user[i]].udpPort != -1) {
                                // send back in invalid command
                                char * message = "must not sent more than one Hello message";
                                send_invalid_command_reply(i, strlen(message), message);
                                // drop connection upon invalid command
                                close(i);
                                FD_CLR(i, &master);
                                destroy_user(i);
                                continue;
                            }
                        }
                        else if (command_type == 1) { // we got a SetStation command
                            // get the station number
                            
                            uint16_t station_number = -1;
                            int bytes_to_read = sizeof(uint16_t);
                            if (recv_all(i, &station_number, &bytes_to_read) == -1) {
                                perror("recv_all");
                                close(i);
                                FD_CLR(i, &master);
                                destroy_user(i);
                                continue;
                            }
                            station_number = ntohs(station_number);

                            // check if user has a udpPort to stream to
                            if (user_data[sockfd_to_user[i]].udpPort == -1) {
                                // send back in invalid command
                                char * message = "must send Hello message first";
                                send_invalid_command_reply(i, strlen(message), message);
                                // drop connection upon invalid command
                                close(i);
                                FD_CLR(i, &master);
                                destroy_user(i);
                                continue;
                            }

                            // check if station num is in range
                            if (station_number >= num_stations || station_number < 0) {
                                // send back in invalid command
                                char * message = "station number out of range";
                                send_invalid_command_reply(i, strlen(message), message);
                                // drop connection upon invalid command
                                close(i);
                                FD_CLR(i, &master);
                                destroy_user(i);
                                continue;
                            }

                            // printf("setting station to %d\n", ntohs(command.number));
                            // update station of user
                            update_user_station(i, station_number);
                            send_announce_reply(i, station_number);
                        }
                        else {
                            // send back in invalid command
                            char * message = "invalid command";
                            send_invalid_command_reply(i, strlen(message), message);
                            
                            // drop connection upon invalid command
                            close(i);
                            FD_CLR(i, &master);
                            destroy_user(i);
                        }
                    }
                } // END handle data from client
            } // END got new incoming connection
        } // END looping through file descriptors

    } // END for(;;)--and you thought it would never end!
}

void *init_user(int sockfd) {
    // add the user to the list of user data
    pthread_mutex_lock(&mutex_user_data);

    if(sockfd > max_sockfd) {
        max_sockfd = sockfd;
        int * more_sockfd_to_user = realloc(sockfd_to_user, sizeof(int) * (max_sockfd + 1));
        if (!more_sockfd_to_user) { perror("realloc"); exit(1); }
        sockfd_to_user = more_sockfd_to_user;
    }

    int running_index = 0;
    while(running_index < max_active_users) {
        if (user_data[running_index].sockfd == -1) {
            break;
        }
        running_index++;
    }
    if (running_index == max_active_users) {
        // printf("reached max active users\n");
        // printf("making new memory\n");
        max_active_users++;
        user_t *more_users = realloc(user_data, sizeof(user_t) * max_active_users);
        if (!more_users) { perror("realloc"); exit(1); }
        user_data = more_users;
    }
    
    // map TCP sockfd to this user index
    user_data[running_index] = (user_t){-1, -1, sockfd};
    sockfd_to_user[sockfd] = running_index;
    // free(user_stream_threads);
    pthread_mutex_unlock(&mutex_user_data);
}
void *update_user_udpPort(int sockfd, int udpPort) {
    pthread_mutex_lock(&mutex_user_data);
    // get the user
    user_t *user = &user_data[sockfd_to_user[sockfd]];
    // set the udpPort
    user->udpPort = udpPort;
    // start the stream thread, now that we have the udpPort
    // pthread_create(&user->streamThread, NULL, send_udp_packet_routine, (void *)sockfd_to_user[sockfd]);
    pthread_mutex_unlock(&mutex_user_data);
}
void *update_user_station(int sockfd, int stationNum) {
    pthread_mutex_lock(&mutex_user_data);
    user_data[sockfd_to_user[sockfd]].stationNum = stationNum;
    pthread_mutex_unlock(&mutex_user_data);
}
void *print_user_data(int index) {
    printf("udpPort: %d, stationNum: %d, sockfd: %d\n", 
        user_data[index].udpPort, user_data[index].stationNum, user_data[index].sockfd);
}

void destroy_user(int sockfd) {
    pthread_mutex_lock(&mutex_user_data);
    // stop the thread streaming to the user
    // pthread_t thread = user_data[sockfd_to_user[sockfd]].streamThread;
    // if (thread != -1) {
    //     pthread_cancel(thread);
    // }
    // "remove" the user from the list of user data
    user_data[sockfd_to_user[sockfd]] = (user_t) {-1, -1, -1};
    // map sockfd to -1
    sockfd_to_user[sockfd] = -1;

    pthread_mutex_unlock(&mutex_user_data);
}


void *get_in_addr(struct sockaddr *sa)
{
    if (sa->sa_family == AF_INET) {
        return &(((struct sockaddr_in*)sa)->sin_addr);
    }

    return &(((struct sockaddr_in6*)sa)->sin6_addr);
}

void send_announce_reply(int fd, int station_num) {
    char* file_path = stations[station_num].filePath;
    int len_file_path = strlen(file_path);

    char *send_buffer = malloc(len_file_path+2);
    if (!send_buffer) {
        perror("malloc in send announce");
        return;
    }
    send_buffer[0] = 3;
    send_buffer[1] = len_file_path;

    memcpy(send_buffer + 2, file_path, len_file_path);

    size_t bytes_to_send = len_file_path + 2;
    if (send_all(fd, send_buffer, &bytes_to_send) == -1)
        perror("send_all");

    free(send_buffer);
}

void send_invalid_command_reply(int fd, size_t message_size, char* message) {
    char *send_buffer = malloc(message_size+2);
    if (!send_buffer) {
        perror("malloc in send invalid command");
        return;
    }

    // type and payload size
    send_buffer[0] = 4;
    send_buffer[1] = message_size;

    memcpy(send_buffer + 2, message, message_size);

    int bytes_to_send = message_size + 2;
    if (send_all(fd, send_buffer, &bytes_to_send) == -1)
        perror("send");

    free(send_buffer);
}

// void init_station(int station_num, const char* station_name) {
//     station_t *station = &station_data[station_num];

//     // open the file
//     int stream_fd = open(station_name, O_RDONLY);
//     if (stream_fd == -1) {
//         perror("open");
//         return;
//     }
//     station->streamFd = stream_fd;
//     station->filePath = station_name;

//     // setup file buffer
//     char stream_buffer[MAX_STREAM_RATE];
//     memset(stream_buffer, 0, MAX_STREAM_RATE);

//     station->fileBufferSize = MAX_STREAM_RATE;
//     memcpy(&station->fileBufferSize, stream_buffer, MAX_STREAM_RATE);


//     // load the first buffer into the stations
//     seek_stations(station_num);
// }

// void seek_stations(int station_num) {
//     station_t *station_info = &station_data[station_num];
//     memset(&station_info->fileBuffer, 0, MAX_STREAM_RATE);
//     int bytes_read = read(station_info->streamFd, &station_info->fileBuffer, MAX_STREAM_RATE);
//     lseek(station_info->streamFd, -16, SEEK_SET);
//     // printf("station info - bytes read: %d, station_fd: %d, filePath: %s, buffersize: %d\n", bytes_read, station_info->streamFd, station_info->filePath, station_info->fileBufferSize);

//     // time to restart the file
//     if (bytes_read == 0) {
//         if (lseek(station_info->streamFd, 0, SEEK_SET) == -1) {
//             perror("fseek");
//         }
//         pthread_t send_announce_thread;
//         pthread_create(&send_announce_thread, NULL, send_announce_routine, (void *)station_num);

//         // load first chunk
//         bytes_read = read(station_info->streamFd, &station_info->fileBuffer, MAX_STREAM_RATE);
//     }
//     station_info->fileBufferSize = bytes_read;
// }


// Parses a buffer into tokens, from cs33 :)
int parse(char buffer[LINE_MAX], char *tokens[LINE_MAX / 2]) {
    const char *regex = " \n\t\f\r";
    char *current_token = strtok(buffer, regex);
    if (current_token == NULL) return 0;

    for (int i = 0; current_token != NULL; i++) {
        tokens[i] = current_token;
        current_token = strtok(NULL, regex);
    }

    return 1;
}