mp3server.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 <string.h>
#include <errno.h>
#include <syslog.h>
#include <sys/types.h>
#include <unistd.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <arpa/inet.h>
#include "mp3server.h"

/**********************************************************************
 * 
 * ZhanYi_10617445_HomeWork04
 * 
 * DESCRIPTION
 * * The purpose of this program is to run as a server, which can  
 *   receive requirement from clients and send datas to clients as
 *   requested.
 * * The data to be sended is specified as mp3 files.
 * * The format of requirement is 
 *                     [<filename>\n\r]
 * * The server listens on a random port choose by kernel. The port
 *   will be printed to the standard out when the relationship between
 *   the program and the port is established.
 *   The port should be used as part of the argument of the client 
 *   end program.
 *
 * USEAGE
 * * ./mp3server <directory_name>
 * * If no argument is present, a default argument '.' (the current
 *   directory) is assumed.
 **********************************************************************/

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

    if (argc > 2) {             /* check the arguments */
        fprintf(stderr, "usage: ./mp3server <directory_name>");
        exit(0);
    }
    if (argc == 2) {
        /* change the current directory if directory name is specified*/
        ret_val = chdir(argv[1]);       
        if (ret_val < 0) 
            err_quit("chdir");
    }
            
    sockfd = server_init(&servaddr); /* initialise the server */
    serve(sockfd);                   /* get ready to accept requirements */
}

int                             /* initialise the server */
server_init(struct sockaddr_in *servaddr)
{
    int sockfd, ret_val;
    
    struct sockaddr_in tempaddr;
    socklen_t templen;

    sockfd = socket(AF_INET, SOCK_STREAM, 0); 
    if (sockfd == -1) 
        err_quit("socket");
        
    bzero(servaddr, sizeof(*servaddr));
    servaddr->sin_family = AF_INET;
    servaddr->sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr->sin_port = 0;

    ret_val = bind(sockfd, (struct sockaddr *)servaddr, sizeof(*servaddr));
    if (ret_val == -1) 
        err_quit("bind");
    
    ret_val = listen(sockfd, QLEN);
    if (ret_val == -1) 
        err_quit("listen");
    
    templen = sizeof(struct sockaddr);
    ret_val = getsockname(sockfd,(struct sockaddr*)&tempaddr,&templen);
    if(ret_val == -1){
        perror("getsockname");
        exit(1);
    }
    
    fprintf(stdout, "Mp3Server is listening on port %hu\n", ntohs(tempaddr.sin_port));
        
    return sockfd;
}
    
void                            /* get ready to accept requirements */
serve(int sockfd)
{
    int mp3fd, clfd;
    ssize_t n;
    char buf[SERV_BUF_SIZE];
    struct sockaddr_in claddr;
    socklen_t clilen = sizeof(claddr);
        
    while (1) {
        clfd = accept(sockfd, (struct sockaddr *)&claddr, &clilen);
        if (clfd < 0) 
            err_quit("accept");
        
        fprintf(stdout, "A client form the address %s connected.\n", inet_ntoa(claddr.sin_addr));
        
        n = recv(clfd, buf, SERV_BUF_SIZE, 0);
        if (n < 0) 
            err_quit("recv");
        
        buf[n-2] = '\0';
        fprintf(stdout, "The client requires the mp3 file: %s\n", buf);
        
        if ((mp3fd = open(buf, O_RDONLY)) < 0) {
            sprintf(buf, "the mp3 file %s do not exist\n", buf);
            err_cont("buf");
        } else {
            while ((n = read(mp3fd, buf, SERV_BUF_SIZE)) > 0) {
                send(clfd, buf, n, 0);
            }
            close(mp3fd);
        }
        close(clfd);
    }
}