mp3client.c

The purpose of this program is to run as a server, which can receive requirement from clients and se

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <syslog.h>
#include <string.h>
#include <unistd.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <arpa/inet.h>
#include "mp3client.h"


/**********************************************************************
 * 
 * ZhanYi_10617445_HomeWork04
 * 
 * DESCRIPTION
 * * The purpose of this program is to run as a client, which can  
 *   send requirement for a mp3 file to the server, receive the mp3 
 *   stream, then decode and play the stream.
 * * The mp3 stream is decoded by functions in mymad.h and mymad.c, 
 *   using libmad library. And the PCM data is processed by functions
 *   in myalsa.h and myalsa.c, using asound library and alsa drivers
 * * The format of requirement is 
 *                     [<filename>\n\r]
 * 
 * USEAGE
 * * "usage: ./mp3client myfiles://<ip_address>:<port>/<filename>
 * * <ip_address> should be a IPv4 address in standard dot notation.
 *   IPv6 is not tested. A host and domain name will not be accepted,
 *   probably leading to the failure of connect function.
 * * <port> is specified by the server(print to the console), other
 *   values can't work.
 * * The prefixed "myfiles://" is needed in the argument passed to 
 *   this program. 
 * * A instance as follow
 *     ./mp3client myfiles://127.0.0.1:2024/ScarboboroughFair.mp3
 **********************************************************************/

int
main(int argc, char *argv[])
{
    int sockfd, ret_val;
    struct sockaddr_in serveraddr;

    ssize_t n;
    char requirement[PATH_MAX+2];
    unsigned char buf[CLI_BUF_SIZE];
        
    if (argc != 2) {            /* check arguments */
        fprintf(stderr, "usage: %s myfiles://<ip_address>:<port>/<filename>\n", argv[0]);
        fprintf(stderr, "for a instance: %s myfiles://127.0.0.1:2024/ScarboboroughFair.mp3\n", argv[0]);
        exit(0);
    }
    
    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd == -1) 
        err_quit("socket");

    /* parse the arguments, init the serveraddr and requirement*/
    parse_init(argv[1], &serveraddr, requirement);
   
    if (connect(sockfd, (struct sockaddr *)&serveraddr, sizeof(serveraddr)) < 0) {
        perror("connect");
        exit(1);
    }
    
    n = send(sockfd, requirement, strlen(requirement), 0);
    if (n == -1) 
        err_quit("send");
    
    mad(sockfd);
} 

void                            /* parse the arguments pass to this program */ 
parse_init(char *arg, struct sockaddr_in *serveraddr, char *requirement) 
{
    int ret_val;
    unsigned int ip;
    char *ip_str, *port_str, *filename;

    ret_val = strncmp(arg, "myfiles://", strlen("myfiles://"));
    if (ret_val == 0) {
        ip_str = arg + strlen("myfiles://");
        port_str = strchr(ip_str, ':');
        if (port_str == NULL)
            err_exit("<port> not specified");
        *port_str++ = '\0';
        filename = strchr(port_str, '/');
        if (filename == NULL)
            err_exit("<filename> not specified");
        *filename++ = '\0';
    } else 
        err_exit("unkown protocol");
        
    /* requirement in this format: [<filename>\n\r] */
    if (sprintf(requirement, "%s\n\r",filename) < 0)
     err_quit("sprintf");
    
    bzero(serveraddr, sizeof(*serveraddr));
    serveraddr->sin_family = AF_INET;
    if (inet_pton(AF_INET, ip_str, &ip) <= 0 ) {
        perror("inet_pton");
        exit(1);
    }
    serveraddr->sin_addr.s_addr = ip;
    serveraddr->sin_port = htons(atoi(port_str));
}